The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Jean-pierre Julien - One of the best experts on this subject based on the ideXlab platform.
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Peripherin Is a Subunit of Peripheral Nerve Neurofilaments: Implications for Differential Vulnerability of CNS and Peripheral Nervous System Axons
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2012Co-Authors: Aidong Yuan, Jean-pierre Julien, Ronald K.h. Liem, Takahiro Sasaki, Asok Kumar, Corrinne M. Peterhoff, Mala V. Rao, Ralph A. NixonAbstract:Peripherin, a neuronal intermediate filament protein implicated in neurodegenerative disease, coexists with the neurofilament triplet proteins (NFL, NFM, and NFH) but has an unknown function. The earlier peak expression of Peripherin than the triplet during brain development and its ability to form homopolymers, unlike the triplet, which are obligate heteropolymers, have supported a widely held view that Peripherin and neurofilament triplet form separate filament systems. Here, we demonstrate, however, that despite a postnatal decline in expression, Peripherin is as abundant as the triplet in the adult PNS and exists in a relatively fixed stoichiometry with these subunits. Peripherin exhibits a distribution pattern identical to those of triplet proteins in sciatic axons and co-localizes with NFL on single neurofilament by immunogold electron microscopy. Peripherin also co-assembles into a single network of filaments containing NFL, NFM, NFH with and without α-internexin in quadruple- or quintuple-transfected SW13 vim (−) cells. Genetically deleting NFL in mice dramatically reduces Peripherin content in sciatic axons. Moreover, Peripherin mutations has been shown to disrupt the neurofilament network in transfected SW13 vim(−) cells. These data show that Peripherin and the neurofilament proteins are functionally interdependent. The results strongly support the view that rather than forming an independent structure, Peripherin is a subunit of neurofilaments in the adult PNS. Our findings provide a basis for its close relationship with neurofilaments in PNS diseases associated with neurofilament accumulation.
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The type III neurofilament Peripherin is expressed in the tuberomammillary neurons of the mouse
BMC neuroscience, 2008Co-Authors: Krister S. Eriksson, Jean-pierre Julien, Roxanne Larivière, Shengwen Zhang, Ling Lin, Emmanuel MignotAbstract:Peripherin, a type III neuronal intermediate filament, is widely expressed in neurons of the peripheral nervous system and in selected central nervous system hindbrain areas with projections towards peripheral structures, such as cranial nerves and spinal cord neurons. Peripherin appears to play a role in neurite elongation during development and axonal regeneration, but its exact function is not known. We noticed high Peripherin expression in the posterior hypothalamus of mice, and decided to investigate further the exact location of expression and function of Peripherin in the mouse posterior hypothalamus. In situ hybridization indicated expression of Peripherin in neurons with a distribution reminiscent of the histaminergic neurons, with little signal in any other part of the forebrain. Immunocytochemical staining for histidine decarboxylase and Peripherin revealed extensive colocalization, showing that Peripherin is produced by histaminergic neurons in all parts of the tuberomammillary nucleus. We next used histamine immunostaining in Peripherin knockout, overexpressing and wild type mice to study if altered Peripherin expression affects these neurons, but could not detect any visible difference in the appearance of these neurons or their axons. Peripherin knockout mice and heterozygotic littermates were used for measurement of locomotor activity, feeding, drinking, and energy expenditure. Both genotypes displayed diurnal rhythms with all the parameters higher during the dark period. The respiratory quotient, an indicator of the type of substrate being utilized, also exhibited a significant diurnal rhythm in both genotypes. The diurnal patterns and the average values of all the recorded parameters for 24 h, daytime and night time were not significantly different between the genotypes, however. In conclusion, we have shown that Peripherin is expressed in the tuberomammillary neurons of the mouse hypothalamus. Monitoring of locomotor activity, feeding, drinking, and energy expenditure in mice either lacking or overexpressing Peripherin did not reveal any difference, so the significance of Peripherin in these neurons remains to be determined. The complete overlap between histidine decarboxylase and Peripherin, both the protein and its mRNA, renders Peripherin a useful new marker for histaminergic neurons in the hypothalamus.
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Defective axonal transport of neurofilament proteins in neurons overexpressing Peripherin.
Journal of Neurochemistry, 2006Co-Authors: Stéphanie Millecamps, Janice Robertson, Roxanne Larivière, Jacques Mallet, Jean-pierre JulienAbstract:Peripherin is a type III neuronal intermediate filament detected in motor neuron inclusions of amyotrophic lateral sclerosis (ALS) patients. We previously reported that overexpression of Peripherin provokes late-onset motor neuron dysfunction in transgenic mice. Here, we show that Peripherin overexpression slows down axonal transport of neurofilament (NF) proteins, and that the transport defect precedes by several months the appearance of axonal spheroids in adult mice. Defective NF transport by Peripherin up-regulation was further confirmed with dorsal root ganglia (DRG) neurons cultured from Peripherin transgenic embryos. Immunofluorescence microscopy and western blotting revealed that excess Peripherin provokes reduction in levels of hyperphosphorylated NF-H species in DRG neurites. Similarly the transport of a green fluorescent protein (GFP)-tagged NF-M, delivered by means of a lentiviral construct, was impaired in DRG neurites overexpressing Peripherin. These results demonstrate that Peripherin overexpression can cause defective transport of type IV NF proteins, a phenomenon that may account for the progressive formation of ALS-like spheroids in axons.
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Up-regulation of Peripherin is associated with alterations in synaptic plasticity in CA1 and CA3 regions of hippocampus
Neurobiology of disease, 2005Co-Authors: Jasna Kriz, Jean-martin Beaulieu, Jean-pierre Julien, Krešimir KrnjevićAbstract:Peripherin is a type III intermediate filament protein normally undetectable in most brain neurons. Here, we report a similar pattern of Peripherin expression in the brains of both mice treated with systemic injections of kainic acid (KA) and in Peripherin transgenic mice (Per mice) over-expressing the normal Peripherin gene under its own promoter. Double-immunofluorescence labeling revealed a partial co-localization of Peripherin with the microtubule-associated protein MAP2, but not with neurofilament proteins. Electrophysiological studies revealed that synaptic plasticity was markedly altered in Per mice: in CA1, long-term potentiation (LTP) was decreased in Per slices (+29 +/- 2.0%, vs. +58 +/- 5.4%, in WT); while in CA3, LTP was increased in Per (+63 +/- 3.5% vs. +43 +/- 2.4.0%). In the hippocampus of Per mice, the levels of MAP2 were decreased, though synaptophysin and PSD95 remained unchanged. These intriguing findings suggest a role of Peripherin in the alteration of hippocampal synaptic plasticity.
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A Frameshift Deletion in Peripherin Gene Associated with Amyotrophic Lateral Sclerosis
The Journal of biological chemistry, 2004Co-Authors: François Gros-louis, Roxanne Larivière, Genevieve Gowing, Sandra Laurent, William Camu, Jean-pierre Bouchard, Vincent Meininger, Guy A. Rouleau, Jean-pierre JulienAbstract:Peripherin is a neuronal intermediate filament associated with inclusion bodies in motor neurons of patients with amyotrophic lateral sclerosis (ALS). A possible Peripherin involvement in ALS pathogenesis has been suggested based on studies with transgenic mouse overexpressors and with a toxic splicing variant of the mouse Peripherin gene. However, the existence of Peripherin gene mutations in human ALS has not yet been documented. Therefore, we screened for sequence variants of the Peripherin gene (PRPH) in a cohort of ALS patients including familial and sporadic cases. We identified 18 polymorphic variants of PRPH detected in both ALS and age-matched control populations. Two additional PRPH variants were discovered in ALS cases but not in 380 control individuals. One variant consisted of a nucleotide insertion in intron 8 (PRPH(IVS8)(-36insA)), whereas the other one consisted of a 1-bp deletion within exon 1 (PRPH(228delC)), predicting a truncated Peripherin species of 85 amino acids. Remarkably, expression of this frameshift Peripherin mutant in SW13 cells resulted in disruption of neurofilament network assembly. These results suggest that PRPH mutations may be responsible for a small percentage of ALS, cases and they provide further support of the view that neurofilament disorganization may contribute to pathogenesis.
Janice Robertson - One of the best experts on this subject based on the ideXlab platform.
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a two hybrid screen identifies an unconventional role for the intermediate filament Peripherin in regulating the subcellular distribution of the snap25 interacting protein sip30
Journal of Neurochemistry, 2014Co-Authors: Benoit J Gentil, Jesse R Mclean, Shangxi Xiao, Beibei Zhao, Heather D Durham, Janice RobertsonAbstract:Peripherin is a type III intermediate filament protein, the expression of which is associated with the acquisition and maintenance of a terminally differentiated neuronal phenotype. Peripherin up-regulation occurs during acute neuronal injury and in degenerating motor neurons of amyotrophic lateral sclerosis. The functional role(s) of Peripherin during normal, injurious, and disease conditions remains unknown, but may be related to differential expression of spliced isoforms. To better understand Peripherin function, we performed a yeast two-hybrid screen on a mouse brain cDNA library using an assembly incompetent Peripherin isoform, Per-61, as bait. We identified new Peripherin interactors with roles in vesicular trafficking, signal transduction, DNA/RNA processing, protein folding, and mitochondrial metabolism. We focused on the interaction of Per-61 and the constitutive isoform, Per-58, with SNAP25 interacting protein 30 (SIP30), a neuronal protein involved in SNAP receptor-dependent exocytosis. We found that Peripherin and SIP30 interacted through coiled-coil domains and colocalized in cytoplasmic aggregates in SW13vim(−) cells. Interestingly, Per-61 and Per-58 differentially altered the subcellular distribution of SIP30 and SNAP25 in primary motor neurons. Our findings suggest a novel role of Peripherin in vesicle trafficking. The functional roles of the intermediate filament Peripherin remain enigmatic. We performed a two-hybrid screen and identified that Peripherin interacts with SIP30 (a), a vesicle trafficking protein. Per-58 and toxic Per-61 isoforms coaggregated with SIP30 in SW13vim(−) cells and altered SIP30 and SNAP25 subcellular localization in primary motor neurons (b). Our results support a role for Peripherin in vesicle trafficking.
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isoform specific expression and ratio changes accompany oxidant induced Peripherin aggregation in a neuroblastoma cell line
Brain Research, 2011Co-Authors: Jesse R Mclean, Janice RobertsonAbstract:Abstract The type III intermediate filament Peripherin is found associated with pathological inclusions present within motor neurons of patients with amyotrophic lateral sclerosis (ALS). Peripherin intra-isoform associations contribute to filament network formation at defined stoichiometric ratios. Distinct biochemical signatures characterize Peripherin isoform expression in traumatic neuronal injury and motor neuron disease, while disruptions to Peripherin alternative splicing or translation are associated with inclusion formation. In our efforts to identify pathological relationships between Peripherin isoform expression and inclusion formation, we provide evidence of Peripherin isoform-specific expression and ratio changes with concomitant, dose-dependent inclusion formation in response to oxidative stress. Upon increasing exposure to physiologically relevant levels of hydrogen peroxide in Neuro-2a cells, we observed a significant increase and decrease in Peripherin isoforms Per-58 and Per-45, respectively, with Peripherin-specific perikaryal aggregation of filaments 10–15 μm in diameter. Interestingly, Peripherin-immunoreactive inclusions showed no overt carbonylation, suggesting that aggregation may serve a physiologically relevant role during oxidative stress. These findings provide novel insight into the biological significance of Peripherin isoforms and inclusion formation, with relevance to the pathology of ALS.
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Distinct biochemical signatures characterize Peripherin isoform expression in both traumatic neuronal injury and motor neuron disease.
Journal of neurochemistry, 2010Co-Authors: Jesse R Mclean, Hsueh-ning Liu, Denise Miletic, Yuan Cheng Weng, Ekaterina Rogaeva, Lorne Zinman, Jasna Kriz, Janice RobertsonAbstract:Peripherin is a type III intermediate filament protein that is up-regulated during neuronal injury and is a major component of pathological inclusions found within degenerating motor neurons of patients with amyotrophic lateral sclerosis (ALS). The relationship between these inclusions and their protein constituents remains largely unknown. We have previously shown that Peripherin expression is characterized by tissue-specific, intra-isoform associations that contribute to filament structure; changes to the normal isoform expression pattern is associated with malformed filaments and intracellular inclusions. Here, we profile Peripherin isoform expression and ratio changes in traumatic neuronal injury, transgenic mouse models of motor neuron disease, and ALS. Extensive western blot analyses of Triton X-100 soluble and insoluble fractions of neuronal tissue from these conditions revealed significant changes in Peripherin isoform content which could be differentiated by electrophoretic banding patterns to produce distinct Peripherin biochemical signatures. Significantly, we found that the pattern of Peripherin expression in ALS most closely approximates that of Peripherin over-expressing mice, but differs with regard to inter-individual variations in isoform-specific expression. Overall, these results provide important insights into complex post-transcriptional processes that may underlie a continuum between Peripherin-mediated neuronal repair and its role in the pathogenesis of motor neuron disease.
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A novel Peripherin isoform generated by alternative translation is required for normal filament network formation.
Journal of neurochemistry, 2008Co-Authors: Jesse R Mclean, Shangxi Xiao, Keigo Miyazaki, Janice RobertsonAbstract:J. Neurochem. (2008) 104, 1663–1673. Abstract Peripherin is a type III neuronal intermediate filament protein detected within the intraneuronal inclusions characteristic of amyotrophic lateral sclerosis. The constitutively expressed Peripherin isoform is encoded by all nine exons of the human and mouse Peripherin genes to generate a protein species of ∼58 kDa on sodium dodecyl sulfate–polyacrylamide gels. Expression of this isoform, termed Per-58, generates a filament network in transfected SW13 vim cells. On immunoblots of cell lysates derived from these transfected cells, we have consistently observed a second Peripherin species of ∼45 kDa. In this study, we show that this species is a novel Peripherin isoform generated through the use of an in-frame downstream initiation codon. This isoform, that we have designated Per-45, is co-expressed together with Per-58 and, thus, constitutive in both human and mouse. Using mutational analysis, we show that Per-45 is required for normal network formation, with the absence of Per-45 leading to irregular filamentous structures. We further show that Peripherin expression in the normal nervous system is characterized by tissue-specific Per-58 : Per-45 isoform ratios. Taken together, these results identify novel processing requirements for Peripherin expression and indicate a hitherto unrecognized role for neuronal intermediate filament network formation through intra-isoform associations.
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Defective axonal transport of neurofilament proteins in neurons overexpressing Peripherin.
Journal of Neurochemistry, 2006Co-Authors: Stéphanie Millecamps, Janice Robertson, Roxanne Larivière, Jacques Mallet, Jean-pierre JulienAbstract:Peripherin is a type III neuronal intermediate filament detected in motor neuron inclusions of amyotrophic lateral sclerosis (ALS) patients. We previously reported that overexpression of Peripherin provokes late-onset motor neuron dysfunction in transgenic mice. Here, we show that Peripherin overexpression slows down axonal transport of neurofilament (NF) proteins, and that the transport defect precedes by several months the appearance of axonal spheroids in adult mice. Defective NF transport by Peripherin up-regulation was further confirmed with dorsal root ganglia (DRG) neurons cultured from Peripherin transgenic embryos. Immunofluorescence microscopy and western blotting revealed that excess Peripherin provokes reduction in levels of hyperphosphorylated NF-H species in DRG neurites. Similarly the transport of a green fluorescent protein (GFP)-tagged NF-M, delivered by means of a lentiviral construct, was impaired in DRG neurites overexpressing Peripherin. These results demonstrate that Peripherin overexpression can cause defective transport of type IV NF proteins, a phenomenon that may account for the progressive formation of ALS-like spheroids in axons.
Robert S Molday - One of the best experts on this subject based on the ideXlab platform.
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Peripherin diverts ciliary ectosome release to photoreceptor disc morphogenesis
The Journal of cell biology, 2017Co-Authors: Robert S Molday, Andrew F. X. GoldbergAbstract:Formation of membrane discs in photoreceptor cells requires evagination of its ciliary plasma membrane by an unknown molecular mechanism. Salinas et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201608081) show that Peripherin (also known as Peripherin-2 or Peripherin-2/rds) diverts membrane traffic to photoreceptor disc formation by inhibiting ectosome release from the cilium.
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Retinal Dystrophies: Functional Genomics to Gene Therapy: Novartis Foundation Symposium 255 - Role of Subunit Assembly in Autosomal Dominant Retinitis Pigmentosa Linked to Mutations in Peripherin 2
Novartis Foundation symposium, 2008Co-Authors: Robert S Molday, Laurie L. Molday, Christopher J R LoewenAbstract:Peripherin 2 is a photoreceptor-specific membrane protein implicated in outer segment disk morphogenesis and linked to various retinopathies including autosomal dominant retinitis pigmentosa (ADRP). Peripherin 2 and ROM1 assemble as a mixture of core noncovalent homomeric and heteromeric tetramers that further link together through disulfide bonds to form higher order oligomers. These complexes are critical for disk rim formation and outer segment structure through interaction with the cGMP-gated channel and other photoreceptor proteins. We have examined the role of subunit assembly in Peripherin 2 targeting to disks, outer segment structure, and photoreceptor degeneration by examining molecular and cellular properties of Peripherin 2 mutants in COS-1 cells and transgenic Xenopus laevis rod photoreceptors. Wild-type (WT) and the ADRP-linked P216L mutant were transported and incorporated into newly formed outer segment disks of transgenic X. laevis. The P216L mutant, however, induced progressive outer segment instability and photoreceptor degeneration possibly through the introduction of a new N-linked oligosaccharide chain. In contrast, the C214S and L185P disease-linked, tetramerization-defective mutants, were retained in the inner segment, but did not affect outer segment structure or induce photoreceptor degeneration. Together, these results indicate that Peripherin 2 mutations can cause ADRP either through a deficiency in WT Peripherin 2 (C214S, 1.185P) or by a dominant negative effect on disk stability (P216L).
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role of subunit assembly in autosomal dominant retinitis pigmentosa linked to mutations in Peripherin 2
Novartis Foundation symposium, 2004Co-Authors: Robert S Molday, Laurie L. Molday, Christopher J R LoewenAbstract:Peripherin 2 is a photoreceptor-specific membrane protein implicated in outer segment disk morphogenesis and linked to various retinopathies including autosomal dominant retinitis pigmentosa (ADRP). Peripherin 2 and ROM1 assemble as a mixture of core noncovalent homomeric and heteromeric tetramers that further link together through disulfide bonds to form higher order oligomers. These complexes are critical for disk rim formation and outer segment structure through interaction with the cGMP-gated channel and other photoreceptor proteins. We have examined the role of subunit assembly in Peripherin 2 targeting to disks, outer segment structure, and photoreceptor degeneration by examining molecular and cellular properties of Peripherin 2 mutants in COS-1 cells and transgenic Xenopus laevis rod photoreceptors. Wild-type (WT) and the ADRP-linked P216L mutant were transported and incorporated into newly formed outer segment disks of transgenic X. laevis. The P216L mutant, however, induced progressive outer segment instability and photoreceptor degeneration possibly through the introduction of a new N-linked oligosaccharide chain. In contrast, the C214S and L185P disease-linked, tetramerization-defective mutants, were retained in the inner segment, but did not affect outer segment structure or induce photoreceptor degeneration. Together, these results indicate that Peripherin 2 mutations can cause ADRP either through a deficiency in WT Peripherin 2 (C214S, 1.185P) or by a dominant negative effect on disk stability (P216L).
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The Role of Subunit Assembly in Peripherin-2 Targeting to Rod Photoreceptor Disk Membranes and Retinitis Pigmentosa
Molecular biology of the cell, 2003Co-Authors: Christopher J R Loewen, Orson L Moritz, Beatrice M. Tam, David S. Papermaster, Robert S MoldayAbstract:Peripherin-2 is a member of the tetraspanin family of membrane proteins that plays a critical role in photoreceptor outer segment disk morphogenesis. Mutations in Peripherin-2 are responsible for various retinal degenerative diseases including autosomal dominant retinitis pigmentosa (ADRP). To identify determinants required for Peripherin-2 targeting to disk membranes and elucidate mechanisms underlying ADRP, we have generated transgenic Xenopus tadpoles expressing wild-type and ADRP-linked Peripherin-2 mutants as green fluorescent fusion proteins in rod photoreceptors. Wild-type Peripherin-2 and P216L and C150S mutants, which assemble as tetramers, targeted to disk membranes as visualized by confocal and electron microscopy. In contrast the C214S and L185P mutants, which form homodimers, but not tetramers, were retained in the rod inner segment. Only the P216L disease mutant induced photoreceptor degeneration. These results indicate that tetramerization is required for Peripherin-2 targeting and incorporation into disk membranes. Tetramerization-defective mutants cause ADRP through a deficiency in wild-type Peripherin-2, whereas tetramerization-competent P216L Peripherin-2 causes ADRP through a dominant negative effect, possibly arising from the introduction of a new oligosaccharide chain that destabilizes disks. Our results further indicate that a checkpoint between the photoreceptor inner and outer segments allows only correctly assembled Peripherin-2 tetramers to be incorporated into nascent disk membranes.
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disulfide mediated oligomerization of Peripherin rds and rom 1 in photoreceptor disk membranes implications for photoreceptor outer segment morphogenesis and degeneration
Journal of Biological Chemistry, 2000Co-Authors: Christopher J R Loewen, Robert S MoldayAbstract:Abstract Peripherin/Rds is a tetraspanning membrane protein that has been implicated in photoreceptor outer segment morphogenesis and inherited retinal degenerative diseases. Together with the structurally related protein, Rom-1, it forms a complex along the rims of rod and cone disc membranes. We have compared the oligomeric structure of these proteins from nonreduced and dithiothreitol reduced membranes by velocity sedimentation, SDS-gel electrophoresis, immunoaffinity chromatography, and chemical cross-linking. Under reducing conditions Peripherin/Rds and Rom-1 existed as homomeric and heteromeric core complexes devoid of intermolecular disulfide bonds. Under nonreducing conditions core complexes associated through intermolecular disulfide bonds to form oligomers. One intermediate-size oligomer contained monomers and disulfide-linked dimers of Peripherin/Rds and Rom-1, while larger oligomers consisted only of disulfide-linked Peripherin/Rds dimers when analyzed on nonreducing SDS gels. Consistent with this result, disc membranes contained twice as much Peripherin/Rds as Rom-1. Peripherin/Rds individually expressed in COS-1 cells also formed disulfide-linked oligomers bridged through Cys-150 residues, whereas Rom-1 showed little tendency to form oligomers. These results indicate that Peripherin/Rds and Rom-1 associate noncovalently to form multisubunit core complexes. Peripherin/Rds containing core complexes interact through specific intermolecular disulfide bonds to form oligomers which may play a crucial role in photoreceptor disc morphogenesis and retinal degenerative diseases.
John G. Flannery - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Peripherin/rds and rom-1 transport in rod photoreceptors of transgenic and knockout animals.
Investigative ophthalmology & visual science, 2006Co-Authors: Edwin S. Lee, Beth Burnside, John G. FlanneryAbstract:During rod photoreceptor development, a connecting cilium composed of a ring of nine microtubule doublets emerges from the inner segment, a specialized region that houses the photoreceptor’s metabolic and biosynthetic machinery. Membranes and proteins amass at the tip of the cilium and eventually organize to form a highly ordered outer segment structure consisting of stacked discs ensheathed by an overlying plasma membrane. Rhodopsin, Peripherin/rds, and rom-1 are integral membrane proteins that incorporate into newly forming discs, although Peripherin/rds and rom-1 localize and function in a region distinct from rhodopsin. The light-sensing pigment, rhodopsin, resides in the lateral membrane of the disc face, whereas Peripherin/rds, rom-1, and the flippase ABCR, are sorted and incorporated into disc rims.1–5 The precise mechanism controlling the partitioning of these molecules into separate regions of the disc remains unknown, although various studies have elucidated several aspects of rhodopsin trafficking from the Golgi to inner segment membranes and to the outer segment.6 Transport of other disc proteins such as Peripherin/rds and rom-1 has been less well characterized even though they play important roles in the development and stability of the outer segment. Peripherin/rds and rom-1 are tetra-spanning membrane proteins possessing a short cytoplasmic N terminus, an inner D2 loop, and a cytoplasmic C-terminal tail.2,7 The D2 loop is the site of noncovalent interactions between Peripherin/rds and rom-1 heterotetramers.8 Both rim proteins are also capable of forming homotetramers, and Peripherin/rds has been found to exist as higher order oligomeric complexes in the outer segment.8,9 Although rom-1 and Peripherin/rds are structurally similar, they share only 30% identical sequences, mainly in the D2 loop.2 Other differences include glycosylation of Peripherin/rds and its twofold higher concentration than rom-1 in photoreceptor outer segments.9 Normal levels of Peripherin/rds expression are necessary for the morphogenesis and maintenance of photoreceptor outer segments. Homozygous Peripherin/rds-knockout mice that do not synthesize Peripherin/rds fail to form outer segments and also undergo a slow degeneration, mirroring the phenotype of rhodopsin null mice.10–14 Even removal of one copy of Peripherin/rds leads to genetic haploinsufficiency; characterized by the formation of disorganized outer segment membrane “whorls” in place of the rod outer segment, moderate rate of apoptotic photoreceptor cell death, and reduction in the electroretinogram (ERG) responses.15 Loss of rom-1 causes discs to become subtly disorganized and slightly shortened.16 Based on this result, the role of rom-1 is thought to add stability to outer segment discs, fine tuning its ultrastructure. It has also been suggested to play an accessory role in Peripherin/rds mediated membrane fusion.17 Peripherin/rds mutations cause a variety of retinal abnormalities in affected individuals.18 Two premature stop mutations, Tyr258ter and Trp316ter, have been implicated in causing adult vitelliform macular dystrophies in humans, which are characterized by gradual photoreceptor degeneration and macroscopic retinal pigment epithelium (RPE) changes.19,20 Because a recent report has shown an outer segment targeting signal is located within residues 317 to 336 of Xenopus Peripherin/rds,21 both Tyr258ter and Trp316ter mutations are predicted to generate C-terminally truncated Peripherin/rds that is missing this transport signal. Whether the deletion affects localization of truncated Peripherin/rds and how the loss of these residues promotes the disease phenotype has yet to be determined. An earlier study of Peripherin/rds and rhodopsin localization in detached feline retinas has provided some clues about the transport of Peripherin/rds. After the retina was separated from the RPE, Peripherin/rds was detectable only in the cytoplasm close to the striated rootlet, whereas rhodopsin delocalized to plasma membranes throughout the photoreceptor.22 The authors suggest that the distinct localization pattern is evidence of separate transport pathways. However, rim proteins may still depend on rhodopsin for transit to the outer segment, as the sheer abundance of rhodopsin transporting to the outer segment could facilitate the movement of other molecules such as rom-1 and Peripherin/rds by providing material flux (i.e., bulk transport) or dominant transport signals. In mammalian photoreceptors, approximately 2000 rhodopsin molecules within 0.1 μm2 of membrane passes through the connecting cilium per minute,23 and rim proteins may transport passively along this gradient. Therefore, we sought to determine unequivocally whether the transport of rim proteins and rhodopsin are interdependent by examining Peripherin/rds and rom-1 trafficking in rhodopsinless rods. Very few studies have explored the transport of rom-1 in rod photoreceptors. Because its protein topology and localization to disc rims are essentially identical with Peripherin/rds, one might expect rom-1 to interact with the same transport partners. However, the cytoplasmic C-terminal tail of rom-1 and Peripherin/rds share only a small number of identical residues and may not share a common transport signal motif.2,24 In a recent study, a fusion protein composed of the C terminus of bovine rom-1 and green fluorescent protein (GFP) was unable to target normally to the outer segments in transgenic Xenopus photoreceptors, suggesting that rom-1 may not possess any transport signals in its C-terminal tail.21 Rom-1, however, is not normally expressed in Xenopus photoreceptors, making this result difficult to interpret. To improve our understanding of the transport mechanism(s) of the disc rim proteins, Peripherin/rds and rom-1, we have taken various approaches using wild-type, knockout, and transgenic animals. First, the normal localization of Peripherin/rds was examined in developing rod photoreceptors, using wild-type rats. Next, rhodopsin-knockout mice were used to determine whether Peripherin/rds and rom-1 are dependent on rhodopsin for transport to the outer segment membrane domain. We also generated transgenic Xenopus to study how the removal of a C-terminal transport signal from Peripherin/rds would affect its targeting to outer segment disc rims. Finally, we examined rds mice to investigate whether rom-1 localizes properly in the absence of Peripherin/rds.
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characterization of Peripherin rds and rom 1 transport in rod photoreceptors of transgenic and knockout animals
Investigative Ophthalmology & Visual Science, 2006Co-Authors: Edwin S. Lee, Beth Burnside, John G. FlanneryAbstract:During rod photoreceptor development, a connecting cilium composed of a ring of nine microtubule doublets emerges from the inner segment, a specialized region that houses the photoreceptor’s metabolic and biosynthetic machinery. Membranes and proteins amass at the tip of the cilium and eventually organize to form a highly ordered outer segment structure consisting of stacked discs ensheathed by an overlying plasma membrane. Rhodopsin, Peripherin/rds, and rom-1 are integral membrane proteins that incorporate into newly forming discs, although Peripherin/rds and rom-1 localize and function in a region distinct from rhodopsin. The light-sensing pigment, rhodopsin, resides in the lateral membrane of the disc face, whereas Peripherin/rds, rom-1, and the flippase ABCR, are sorted and incorporated into disc rims.1–5 The precise mechanism controlling the partitioning of these molecules into separate regions of the disc remains unknown, although various studies have elucidated several aspects of rhodopsin trafficking from the Golgi to inner segment membranes and to the outer segment.6 Transport of other disc proteins such as Peripherin/rds and rom-1 has been less well characterized even though they play important roles in the development and stability of the outer segment. Peripherin/rds and rom-1 are tetra-spanning membrane proteins possessing a short cytoplasmic N terminus, an inner D2 loop, and a cytoplasmic C-terminal tail.2,7 The D2 loop is the site of noncovalent interactions between Peripherin/rds and rom-1 heterotetramers.8 Both rim proteins are also capable of forming homotetramers, and Peripherin/rds has been found to exist as higher order oligomeric complexes in the outer segment.8,9 Although rom-1 and Peripherin/rds are structurally similar, they share only 30% identical sequences, mainly in the D2 loop.2 Other differences include glycosylation of Peripherin/rds and its twofold higher concentration than rom-1 in photoreceptor outer segments.9 Normal levels of Peripherin/rds expression are necessary for the morphogenesis and maintenance of photoreceptor outer segments. Homozygous Peripherin/rds-knockout mice that do not synthesize Peripherin/rds fail to form outer segments and also undergo a slow degeneration, mirroring the phenotype of rhodopsin null mice.10–14 Even removal of one copy of Peripherin/rds leads to genetic haploinsufficiency; characterized by the formation of disorganized outer segment membrane “whorls” in place of the rod outer segment, moderate rate of apoptotic photoreceptor cell death, and reduction in the electroretinogram (ERG) responses.15 Loss of rom-1 causes discs to become subtly disorganized and slightly shortened.16 Based on this result, the role of rom-1 is thought to add stability to outer segment discs, fine tuning its ultrastructure. It has also been suggested to play an accessory role in Peripherin/rds mediated membrane fusion.17 Peripherin/rds mutations cause a variety of retinal abnormalities in affected individuals.18 Two premature stop mutations, Tyr258ter and Trp316ter, have been implicated in causing adult vitelliform macular dystrophies in humans, which are characterized by gradual photoreceptor degeneration and macroscopic retinal pigment epithelium (RPE) changes.19,20 Because a recent report has shown an outer segment targeting signal is located within residues 317 to 336 of Xenopus Peripherin/rds,21 both Tyr258ter and Trp316ter mutations are predicted to generate C-terminally truncated Peripherin/rds that is missing this transport signal. Whether the deletion affects localization of truncated Peripherin/rds and how the loss of these residues promotes the disease phenotype has yet to be determined. An earlier study of Peripherin/rds and rhodopsin localization in detached feline retinas has provided some clues about the transport of Peripherin/rds. After the retina was separated from the RPE, Peripherin/rds was detectable only in the cytoplasm close to the striated rootlet, whereas rhodopsin delocalized to plasma membranes throughout the photoreceptor.22 The authors suggest that the distinct localization pattern is evidence of separate transport pathways. However, rim proteins may still depend on rhodopsin for transit to the outer segment, as the sheer abundance of rhodopsin transporting to the outer segment could facilitate the movement of other molecules such as rom-1 and Peripherin/rds by providing material flux (i.e., bulk transport) or dominant transport signals. In mammalian photoreceptors, approximately 2000 rhodopsin molecules within 0.1 μm2 of membrane passes through the connecting cilium per minute,23 and rim proteins may transport passively along this gradient. Therefore, we sought to determine unequivocally whether the transport of rim proteins and rhodopsin are interdependent by examining Peripherin/rds and rom-1 trafficking in rhodopsinless rods. Very few studies have explored the transport of rom-1 in rod photoreceptors. Because its protein topology and localization to disc rims are essentially identical with Peripherin/rds, one might expect rom-1 to interact with the same transport partners. However, the cytoplasmic C-terminal tail of rom-1 and Peripherin/rds share only a small number of identical residues and may not share a common transport signal motif.2,24 In a recent study, a fusion protein composed of the C terminus of bovine rom-1 and green fluorescent protein (GFP) was unable to target normally to the outer segments in transgenic Xenopus photoreceptors, suggesting that rom-1 may not possess any transport signals in its C-terminal tail.21 Rom-1, however, is not normally expressed in Xenopus photoreceptors, making this result difficult to interpret. To improve our understanding of the transport mechanism(s) of the disc rim proteins, Peripherin/rds and rom-1, we have taken various approaches using wild-type, knockout, and transgenic animals. First, the normal localization of Peripherin/rds was examined in developing rod photoreceptors, using wild-type rats. Next, rhodopsin-knockout mice were used to determine whether Peripherin/rds and rom-1 are dependent on rhodopsin for transport to the outer segment membrane domain. We also generated transgenic Xenopus to study how the removal of a C-terminal transport signal from Peripherin/rds would affect its targeting to outer segment disc rims. Finally, we examined rds mice to investigate whether rom-1 localizes properly in the absence of Peripherin/rds.
Cecilia Bucci - One of the best experts on this subject based on the ideXlab platform.
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Charcot–Marie–Tooth type 2B disease-causing RAB7A mutant proteins show altered interaction with the neuronal intermediate filament Peripherin
Acta Neuropathologica, 2013Co-Authors: Laura Cogli, Cinzia Progida, Claire L. Thomas, Bradley Spencer-dene, Claudia Donno, Giampietro Schiavo, Cecilia BucciAbstract:Charcot–Marie–Tooth type 2B (CMT2B) is a peripheral ulcero-mutilating neuropathy caused by four missense mutations in the rab7a gene. CMT2B is clinically characterized by prominent sensory loss, distal muscle weakness leading to muscle atrophy, high frequency of foot ulcers and infections that often results in toe amputations. RAB7A is a ubiquitous small GTPase, which controls transport to late endocytic compartments. Although the biochemical and functional properties of disease-causing RAB7A mutant proteins have been investigated, it is not yet clear how the disease originates. To understand how mutations in a ubiquitous protein specifically affect peripheral neurons, we performed a two-hybrid screen using a dorsal root ganglia cDNA library with the purpose of identifying RAB7A interactors specific for these cells. We identified Peripherin, an intermediate filament protein expressed primarily in peripheral neurons, as a putative RAB7A interacting protein. The interaction was confirmed by co-immunoprecipitation and pull-down experiments, and established that the interaction is direct using recombinant proteins. Silencing or overexpression of wild type RAB7A changed the soluble/insoluble rate of Peripherin indicating that RAB7A is important for Peripherin organization and function. In addition, disease-causing RAB7A mutant proteins bind more strongly to Peripherin and their expression causes a significant increase in the amount of soluble Peripherin. Since Peripherin plays a role not only in neurite outgrowth during development but also in axonal regeneration after injury, these data suggest that the altered interaction between disease-causing RAB7A mutants and Peripherin could play an important role in CMT2B neuropathy.
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charcot marie tooth type 2b disease causing rab7a mutant proteins show altered interaction with the neuronal intermediate filament Peripherin
Acta Neuropathologica, 2013Co-Authors: Laura Cogli, Cinzia Progida, Claudia Donno, Giampietro Schiavo, Claire Thomas, Bradley Spencerdene, Cecilia BucciAbstract:Charcot–Marie–Tooth type 2B (CMT2B) is a peripheral ulcero-mutilating neuropathy caused by four missense mutations in the rab7a gene. CMT2B is clinically characterized by prominent sensory loss, distal muscle weakness leading to muscle atrophy, high frequency of foot ulcers and infections that often results in toe amputations. RAB7A is a ubiquitous small GTPase, which controls transport to late endocytic compartments. Although the biochemical and functional properties of disease-causing RAB7A mutant proteins have been investigated, it is not yet clear how the disease originates. To understand how mutations in a ubiquitous protein specifically affect peripheral neurons, we performed a two-hybrid screen using a dorsal root ganglia cDNA library with the purpose of identifying RAB7A interactors specific for these cells. We identified Peripherin, an intermediate filament protein expressed primarily in peripheral neurons, as a putative RAB7A interacting protein. The interaction was confirmed by co-immunoprecipitation and pull-down experiments, and established that the interaction is direct using recombinant proteins. Silencing or overexpression of wild type RAB7A changed the soluble/insoluble rate of Peripherin indicating that RAB7A is important for Peripherin organization and function. In addition, disease-causing RAB7A mutant proteins bind more strongly to Peripherin and their expression causes a significant increase in the amount of soluble Peripherin. Since Peripherin plays a role not only in neurite outgrowth during development but also in axonal regeneration after injury, these data suggest that the altered interaction between disease-causing RAB7A mutants and Peripherin could play an important role in CMT2B neuropathy.