The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Scott T. Brady - One of the best experts on this subject based on the ideXlab platform.
-
engagement of neurotropic viruses in Fast Axonal Transport mechanisms potential role of host kinases and implications for neuronal dysfunction
Frontiers in Cellular Neuroscience, 2021Co-Authors: Alexsia Richards, Scott T. Brady, Sarah H Berth, Gerardo MorfiniAbstract:Much remains unknown about mechanisms sustaining the various stages in the life cycle of neurotropic viruses. An understanding of those mechanisms operating before their replication and propagation could advance the development of effective anti-viral strategies. Here, we review our current knowledge of strategies used by neurotropic viruses to undergo bidirectional movement along axons. We discuss how the invasion strategies used by specific viruses might influence their mode of interaction with selected components of the host's Fast Axonal Transport (FAT) machinery, including specialized membrane-bounded organelles and microtubule-based motor proteins. As part of this discussion, we provide a critical evaluation of various reported interactions among viral and motor proteins and highlight limitations of some in vitro approaches that led to their identification. Based on a large body of evidence documenting activation of host kinases by neurotropic viruses, and on recent work revealing regulation of FAT through phosphorylation-based mechanisms, we posit a potential role of host kinases on the engagement of viruses in retrograde FAT. Finally, we briefly describe recent evidence linking aberrant activation of kinase pathways to deficits in FAT and neuronal degeneration in the context of human neurodegenerative diseases. Based on these findings, we speculate that neurotoxicity elicited by viral infection may involve deregulation of host kinases involved in the regulation of FAT and other cellular processes sustaining neuronal function and survival.
-
defined tau phosphospecies differentially inhibit Fast Axonal Transport through activation of two independent signaling pathways
Frontiers in Molecular Neuroscience, 2021Co-Authors: Sarah L Morris, Gerardo Morfini, Scott T. Brady, Mingying Tsai, Sarah Aloe, Karin Bechberger, Svenja KonigAbstract:Tau protein is subject to phosphorylation by multiple kinases at more than 80 different sites. Some of these sites are associated with tau pathology and neurodegeneration, but other sites are modified in normal tau as well as in pathological tau. Although phosphorylation of tau at residues in the microtubule-binding repeats is thought to reduce tau association with microtubules, the functional consequences of other sites are poorly understood. The AT8 antibody recognizes a complex phosphoepitope site on tau that is detectable in a healthy brain but significantly increased in Alzheimer's disease (AD) and other tauopathies. Previous studies showed that phosphorylation of tau at the AT8 site leads to exposure of an N-terminal sequence that promotes activation of a protein phosphatase 1 (PP1)/glycogen synthase 3 (GSK3) signaling pathway, which inhibits kinesin-1-based anterograde Fast Axonal Transport (FAT). This finding suggests that phosphorylation may control tau conformation and function. However, the AT8 includes three distinct phosphorylated amino acids that may be differentially phosphorylated in normal and disease conditions. To evaluate the effects of specific phosphorylation sites in the AT8 epitope, recombinant, pseudophosphorylated tau proteins were perfused into the isolated squid axoplasm preparation to determine their effects on Axonal signaling pathways and FAT. Results from these studies suggest a mechanism where specific phosphorylation events differentially impact tau conformation, promoting activation of independent signaling pathways that differentially affect FAT. Implications of findings here to our understanding of tau function in health and disease conditions are discussed.
-
pseudophosphorylation of tau at s422 enhances sds stable dimer formation and impairs both anterograde and retrograde Fast Axonal Transport
Experimental Neurology, 2016Co-Authors: Chelsea T Tiernan, Gerardo Morfini, Scott T. Brady, Benjamin Combs, Kristine Cox, Scott E Counts, Nicholas M KanaanAbstract:In Alzheimer's disease (AD), tau undergoes numerous modifications, including increased phosphorylation at serine-422 (pS422). In the human brain, pS422 tau protein is found in prodromal AD, correlates well with cognitive decline and neuropil thread pathology, and appears associated with increased oligomer formation and exposure of the N-terminal phosphatase-activating domain (PAD). However, whether S422 phosphorylation contributes to toxic mechanisms associated with disease-related forms of tau remains unknown. Here, we report that S422-pseudophosphorylated tau (S422E) lengthens the nucleation phase of aggregation without altering the extent of aggregation or the types of aggregates formed. When compared to unmodified tau aggregates, the S422E modification significantly increased the amount of SDS-stable tau dimers, despite similar levels of immunoreactivity with an oligomer-selective antibody (TOC1) and another antibody that reports PAD exposure (TNT1). Vesicle motility assays in isolated squid axoplasm further revealed that S422E tau monomers inhibited anterograde, kinesin-1 dependent Fast Axonal Transport (FAT). Unexpectedly, and unlike unmodified tau aggregates, which selectively inhibit anterograde FAT, aggregates composed of S422E tau were found to inhibit both anterograde and retrograde FAT. Highlighting the relevance of these findings to human disease, pS422 tau was found to colocalize with tau oligomers and with a fraction of tau showing increased PAD exposure in the human AD brain. This study identifies novel effects of pS422 on tau biochemical properties, including prolonged nucleation and enhanced dimer formation, which correlate with a distinct inhibitory effect on FAT. Taken together, these findings identify a novel mechanistic basis by which pS422 confers upon tau a toxic effect that may directly contribute to Axonal dysfunction in AD and other tauopathies.
-
Fast Axonal Transport in isolated axoplasm from the squid giant axon
Methods in Cell Biology, 2016Co-Authors: Yuyu Song, Gerardo Morfini, Scott T. Brady, Minsu KangAbstract:Abstract The giant axon of the squid provides a unique cell biological model for analyzing the biochemistry and cell biology of the axon. These axons may exceed 500 μm in diameter and can be readily dissected. Once the surrounding small axons and connective tissue are removed, the axoplasm can be extruded as an intact cylinder of isolated cytoplasm. This isolated axoplasm is morphologically indistinguishable from the intact axon, but without permeability barriers. Fast Axonal Transport will continue for more than 4 h after extrusion and can be visualized in real time. By perfusing defined concentrations of proteins and/or reagents into the axoplasm, this preparation represents a powerful model for study of intracellular trafficking and its underlying molecular mechanisms.
-
effects of eribulin vincristine paclitaxel and ixabepilone on Fast Axonal Transport and kinesin 1 driven microtubule gliding implications for chemotherapy induced peripheral neuropathy
Neurotoxicology, 2013Co-Authors: Nichole E Lapointe, Gerardo Morfini, Scott T. Brady, Stuart C Feinstein, Leslie Wilson, Mary Ann JordanAbstract:Chemotherapy-induced peripheral neuropathy (CIPN) is a serious, painful and dose-limiting side effect of cancer drugs that target microtubules. The mechanisms underlying the neuronal damage are unknown, but may include disruption of Fast Axonal Transport, an essential microtubule-based process that moves cellular components over long distances between neuronal cell bodies and nerve terminals. This idea is supported by the “dying back” pattern of degeneration observed in CIPN, and by the selective vulnerability of sensory neurons bearing the longest Axonal projections. In this study, we test the hypothesis that microtubule-targeting drugs disrupt Fast Axonal Transport using vesicle motility assays in isolated squid axoplasm and a cell-free microtubule gliding assay with defined components. We compare four clinically-used drugs, eribulin, vincristine, paclitaxel and ixabepilone. Of these, eribulin is associated with a relatively low incidence of severe neuropathy, while vincristine has a relatively high incidence. In vesicle motility assays, we found that all four drugs inhibited anterograde (conventional kinesin-dependent) Fast Axonal Transport, with the potency being vincristine = ixabepilone > paclitaxel = eribulin. Interestingly, eribulin and paclitaxel did not inhibit retrograde (cytoplasmic dynein-dependent) Fast Axonal Transport, in contrast to vincristine and ixabepilone. Similarly, vincristine and ixabepilone both exerted significant inhibitory effects in an in vitro microtubule gliding assay consisting of recombinant kinesin (kinesin-1) and microtubules composed of purified bovine brain tubulin, whereas paclitaxel and eribulin had negligible effects. Our results suggest that (i) inhibition of microtubule-based Fast Axonal Transport may be a significant contributor to neurotoxicity induced by microtubule-targeting drugs, and (ii) that individual microtubule-targeting drugs affect Fast Axonal Transport through different mechanisms.
Gerardo Morfini - One of the best experts on this subject based on the ideXlab platform.
-
engagement of neurotropic viruses in Fast Axonal Transport mechanisms potential role of host kinases and implications for neuronal dysfunction
Frontiers in Cellular Neuroscience, 2021Co-Authors: Alexsia Richards, Scott T. Brady, Sarah H Berth, Gerardo MorfiniAbstract:Much remains unknown about mechanisms sustaining the various stages in the life cycle of neurotropic viruses. An understanding of those mechanisms operating before their replication and propagation could advance the development of effective anti-viral strategies. Here, we review our current knowledge of strategies used by neurotropic viruses to undergo bidirectional movement along axons. We discuss how the invasion strategies used by specific viruses might influence their mode of interaction with selected components of the host's Fast Axonal Transport (FAT) machinery, including specialized membrane-bounded organelles and microtubule-based motor proteins. As part of this discussion, we provide a critical evaluation of various reported interactions among viral and motor proteins and highlight limitations of some in vitro approaches that led to their identification. Based on a large body of evidence documenting activation of host kinases by neurotropic viruses, and on recent work revealing regulation of FAT through phosphorylation-based mechanisms, we posit a potential role of host kinases on the engagement of viruses in retrograde FAT. Finally, we briefly describe recent evidence linking aberrant activation of kinase pathways to deficits in FAT and neuronal degeneration in the context of human neurodegenerative diseases. Based on these findings, we speculate that neurotoxicity elicited by viral infection may involve deregulation of host kinases involved in the regulation of FAT and other cellular processes sustaining neuronal function and survival.
-
defined tau phosphospecies differentially inhibit Fast Axonal Transport through activation of two independent signaling pathways
Frontiers in Molecular Neuroscience, 2021Co-Authors: Sarah L Morris, Gerardo Morfini, Scott T. Brady, Mingying Tsai, Sarah Aloe, Karin Bechberger, Svenja KonigAbstract:Tau protein is subject to phosphorylation by multiple kinases at more than 80 different sites. Some of these sites are associated with tau pathology and neurodegeneration, but other sites are modified in normal tau as well as in pathological tau. Although phosphorylation of tau at residues in the microtubule-binding repeats is thought to reduce tau association with microtubules, the functional consequences of other sites are poorly understood. The AT8 antibody recognizes a complex phosphoepitope site on tau that is detectable in a healthy brain but significantly increased in Alzheimer's disease (AD) and other tauopathies. Previous studies showed that phosphorylation of tau at the AT8 site leads to exposure of an N-terminal sequence that promotes activation of a protein phosphatase 1 (PP1)/glycogen synthase 3 (GSK3) signaling pathway, which inhibits kinesin-1-based anterograde Fast Axonal Transport (FAT). This finding suggests that phosphorylation may control tau conformation and function. However, the AT8 includes three distinct phosphorylated amino acids that may be differentially phosphorylated in normal and disease conditions. To evaluate the effects of specific phosphorylation sites in the AT8 epitope, recombinant, pseudophosphorylated tau proteins were perfused into the isolated squid axoplasm preparation to determine their effects on Axonal signaling pathways and FAT. Results from these studies suggest a mechanism where specific phosphorylation events differentially impact tau conformation, promoting activation of independent signaling pathways that differentially affect FAT. Implications of findings here to our understanding of tau function in health and disease conditions are discussed.
-
hiv glycoprotein gp120 impairs Fast Axonal Transport by activating tak1 signaling pathways
Asn Neuro, 2016Co-Authors: Sarah Berth, Yuyu Song, Gerardo Morfini, Nichole A Mesnardhoaglin, Bin Wang, Hajwa Kim, Maria SaparAbstract:Sensory neuropathies are the most common neurological complication of HIV. Of these, distal sensory polyneuropathy (DSP) is directly caused by HIV infection and characterized by length-dependent Axonal degeneration of dorsal root ganglion (DRG) neurons. Mechanisms for Axonal degeneration in DSP remain unclear, but recent experiments revealed that the HIV glycoprotein gp120 is internalized and localized within axons of DRG neurons. Based on these findings, we investigated whether intra-Axonal gp120 might impair Fast Axonal Transport (FAT), a cellular process critical for appropriate maintenance of the Axonal compartment. Significantly, we found that gp120 severely impaired both anterograde and retrograde FAT. Providing a mechanistic basis for these effects, pharmacological experiments revealed an involvement of various phosphotransferases in this toxic effect, including members of mitogen-activated protein kinase pathways (Tak-1, p38, and c-Jun N-terminal Kinase (JNK)), inhibitor of kappa-B-kinase 2 (IKK2), and PP1. Biochemical experiments and Axonal outgrowth assays in cell lines and primary cultures extended these findings. Impairments in neurite outgrowth in DRG neurons by gp120 were rescued using a Tak-1 inhibitor, implicating a Tak-1 mitogen-activated protein kinase pathway in gp120 neurotoxicity. Taken together, these observations indicate that kinase-based impairments in FAT represent a novel mechanism underlying gp120 neurotoxicity consistent with the dying-back degeneration seen in DSP. Targeting gp120-based impairments in FAT with specific kinase inhibitors might provide a novel therapeutic strategy to prevent Axonal degeneration in DSP.
-
pseudophosphorylation of tau at s422 enhances sds stable dimer formation and impairs both anterograde and retrograde Fast Axonal Transport
Experimental Neurology, 2016Co-Authors: Chelsea T Tiernan, Gerardo Morfini, Scott T. Brady, Benjamin Combs, Kristine Cox, Scott E Counts, Nicholas M KanaanAbstract:In Alzheimer's disease (AD), tau undergoes numerous modifications, including increased phosphorylation at serine-422 (pS422). In the human brain, pS422 tau protein is found in prodromal AD, correlates well with cognitive decline and neuropil thread pathology, and appears associated with increased oligomer formation and exposure of the N-terminal phosphatase-activating domain (PAD). However, whether S422 phosphorylation contributes to toxic mechanisms associated with disease-related forms of tau remains unknown. Here, we report that S422-pseudophosphorylated tau (S422E) lengthens the nucleation phase of aggregation without altering the extent of aggregation or the types of aggregates formed. When compared to unmodified tau aggregates, the S422E modification significantly increased the amount of SDS-stable tau dimers, despite similar levels of immunoreactivity with an oligomer-selective antibody (TOC1) and another antibody that reports PAD exposure (TNT1). Vesicle motility assays in isolated squid axoplasm further revealed that S422E tau monomers inhibited anterograde, kinesin-1 dependent Fast Axonal Transport (FAT). Unexpectedly, and unlike unmodified tau aggregates, which selectively inhibit anterograde FAT, aggregates composed of S422E tau were found to inhibit both anterograde and retrograde FAT. Highlighting the relevance of these findings to human disease, pS422 tau was found to colocalize with tau oligomers and with a fraction of tau showing increased PAD exposure in the human AD brain. This study identifies novel effects of pS422 on tau biochemical properties, including prolonged nucleation and enhanced dimer formation, which correlate with a distinct inhibitory effect on FAT. Taken together, these findings identify a novel mechanistic basis by which pS422 confers upon tau a toxic effect that may directly contribute to Axonal dysfunction in AD and other tauopathies.
-
Fast Axonal Transport in isolated axoplasm from the squid giant axon
Methods in Cell Biology, 2016Co-Authors: Yuyu Song, Gerardo Morfini, Scott T. Brady, Minsu KangAbstract:Abstract The giant axon of the squid provides a unique cell biological model for analyzing the biochemistry and cell biology of the axon. These axons may exceed 500 μm in diameter and can be readily dissected. Once the surrounding small axons and connective tissue are removed, the axoplasm can be extruded as an intact cylinder of isolated cytoplasm. This isolated axoplasm is morphologically indistinguishable from the intact axon, but without permeability barriers. Fast Axonal Transport will continue for more than 4 h after extrusion and can be visualized in real time. By perfusing defined concentrations of proteins and/or reagents into the axoplasm, this preparation represents a powerful model for study of intracellular trafficking and its underlying molecular mechanisms.
Nicholas M Kanaan - One of the best experts on this subject based on the ideXlab platform.
-
pseudophosphorylation of tau at s422 enhances sds stable dimer formation and impairs both anterograde and retrograde Fast Axonal Transport
Experimental Neurology, 2016Co-Authors: Chelsea T Tiernan, Gerardo Morfini, Scott T. Brady, Benjamin Combs, Kristine Cox, Scott E Counts, Nicholas M KanaanAbstract:In Alzheimer's disease (AD), tau undergoes numerous modifications, including increased phosphorylation at serine-422 (pS422). In the human brain, pS422 tau protein is found in prodromal AD, correlates well with cognitive decline and neuropil thread pathology, and appears associated with increased oligomer formation and exposure of the N-terminal phosphatase-activating domain (PAD). However, whether S422 phosphorylation contributes to toxic mechanisms associated with disease-related forms of tau remains unknown. Here, we report that S422-pseudophosphorylated tau (S422E) lengthens the nucleation phase of aggregation without altering the extent of aggregation or the types of aggregates formed. When compared to unmodified tau aggregates, the S422E modification significantly increased the amount of SDS-stable tau dimers, despite similar levels of immunoreactivity with an oligomer-selective antibody (TOC1) and another antibody that reports PAD exposure (TNT1). Vesicle motility assays in isolated squid axoplasm further revealed that S422E tau monomers inhibited anterograde, kinesin-1 dependent Fast Axonal Transport (FAT). Unexpectedly, and unlike unmodified tau aggregates, which selectively inhibit anterograde FAT, aggregates composed of S422E tau were found to inhibit both anterograde and retrograde FAT. Highlighting the relevance of these findings to human disease, pS422 tau was found to colocalize with tau oligomers and with a fraction of tau showing increased PAD exposure in the human AD brain. This study identifies novel effects of pS422 on tau biochemical properties, including prolonged nucleation and enhanced dimer formation, which correlate with a distinct inhibitory effect on FAT. Taken together, these findings identify a novel mechanistic basis by which pS422 confers upon tau a toxic effect that may directly contribute to Axonal dysfunction in AD and other tauopathies.
-
heat shock protein 70 prevents both tau aggregation and the inhibitory effects of preexisting tau aggregates on Fast Axonal Transport
Biochemistry, 2011Co-Authors: Kristina R Patterson, Gerardo Morfini, Scott T. Brady, Benjamin Combs, Nicholas M Kanaan, Sarah M Ward, Kellen Voss, Chris T Gamblin, Lester I BinderAbstract:Tau is a microtubule-associated protein predominantly expressed in axons where it is involved in the maintenance and stabilization of microtubules.1 Under physiological conditions, tau is a soluble protein with limited secondary structure.2 However, in Alzheimer's disease (AD), tau dissociates from microtubules and self-associates to form both fibrillar and prefibrillar oligomeric aggregates.3,4 Aggregated forms of tau are also found in various other tauopathies, including Pick's disease, corticobasal degeneration, and progressive supranuclear palsy.5 Importantly, the identification of mutations in the tau gene that cause hereditary tauopathies demonstrates that tau dysfunction is sufficient to cause neuronal degeneration. Neurofibrillary tangles (NFTs), a pathological hallmark of AD and other tauopathies, are composed of fibrillar tau aggregates and positively correlate with cognitive decline.6 However, recent evidence suggests that prefibrillar oligomeric tau aggregates may represent the main toxic species.7 For instance, neurodegeneration occurs in some tau overexpression animal models that lack overt neurofibrillary pathology.8,9 Another study demonstrated that levels of early multimeric tau aggregates that preceded neurofibrillary pathology correlated better with memory deficits.10 Moreover, suppression of tau expression improved memory function without affecting existing NFTs.11,12 The exact mechanisms underlying tau toxicity remain a matter of debate. However, recent experiments demonstrated that abnormal activation of kinase-based pathways and disruption of Fast Axonal Transport (FAT) represent toxic gains of function associated with aggregated but not soluble tau species.13–15 Specifically, experiments in isolated squid axoplasm revealed that aggregated tau activates a protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3)-dependent signaling pathway that results in the inhibition of conventional kinesin-dependent anterograde FAT.13 Given that aggregated tau pathology is a common denominator in several neurodegenerative diseases and that tau aggregates are demonstrably toxic, it follows that prevention of tau aggregation represents a reasonable therapeutic objective. Molecular chaperones make up a highly conserved family of related proteins that prevent protein misfolding and aggregation. Chaperone involvement has been implicated in several neurodegenerative diseases, including Parkinson's disease, Huntington's disease, and AD.16–20 In particular, molecular chaperones of the Hsp70 family are upregulated in AD and attenuate toxicity in a variety of neurodegenerative disease models.21 Hsp70 has been found to facilitate microtubule binding of tau and is associated with decreased levels of insoluble tau.22,23 In addition, Hsp70 facilitates the degradation of insoluble tau aggregates via a direct interaction with CHIP (carboxyl terminus of the Hsc70-interacting protein), a ubiquitin ligase,23 or BAG2 (BCL2-associated athanogene 2), a cochaperone.24 Taken together, the available data suggest that Hsp70 attenuates tau toxicity by maintaining tau in a soluble, nonaggregated state and by facilitating the degradation of aggregated tau species. However, the exact tau aggregate species targeted by Hsp70 chaperones remains unknown. Moreover, specific cellular processes protected by Hsp70 chaperones have not been identified, and thus data showing reduction of tau toxicity remain largely correlative. In this study, we demonstrate that Hsp70 directly inhibits tau aggregation by a mechanism involving preferential associations with soluble, monomeric and prefibrillar oligomeric tau species. In addition, Hsp70 prevents the toxic effect of preformed tau aggregates on anterograde FAT. When added to preformed tau aggregates in vitro, Hsp70 did not appreciably dissociate tau filaments. Interestingly, Hsp70 was found to associate preferentially with oligomeric versus fibrillar tau aggregates, suggesting that oligomeric aggregates may represent the main toxic species associated with aggregated tau.
Nobutaka Hirokawa - One of the best experts on this subject based on the ideXlab platform.
-
kinesin 1 hsc70 dependent mechanism of slow Axonal Transport and its relation to Fast Axonal Transport
Biophysical Journal, 2011Co-Authors: Sumio Terada, Yosuke Takei, Masataka Kinjo, Makoto Aihara, Nobutaka HirokawaAbstract:Cytoplasmic protein Transport in axons (‘slow Axonal Transport’) is essential for neuronal homeostasis, and involves Kinesin-1, the same motor for membranous organelle Transport (‘Fast Axonal Transport’). However, both molecular mechanisms of slow Axonal Transport and difference in usage of Kinesin-1 between slow and Fast Axonal Transport have been elusive. Here, we show that slow Axonal Transport depends on the interaction between the DnaJ-like domain of the kinesin light chain in the Kinesin-1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin-1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein Transport and reinforced membranous organelle Transport, indicating that this domain might have a function as a switchover system between slow and Fast Transport by Hsc70. Transgenic mice overexpressing a dominant-negative form of the domain showed delayed slow Transport, accelerated Fast Transport and optic axonopathy without elevation of intraocular pressure. These findings provide a basis for the regulatory mechanism of intracellular Transport and its intriguing implication in the understanding of neuronal dysfunction such as normal tension glaucoma.View Large Image | View Hi-Res Image | Download PowerPoint Slide
-
kinesin 1 hsc70 dependent mechanism of slow Axonal Transport and its relation to Fast Axonal Transport
The EMBO Journal, 2010Co-Authors: Yosuke Takei, Sumio Terada, Masataka Kinjo, Makoto Aihara, Nobutaka HirokawaAbstract:Cytoplasmic protein Transport in axons (‘slow Axonal Transport’) is essential for neuronal homeostasis, and involves Kinesin‐1, the same motor for membranous organelle Transport (‘Fast Axonal Transport’). However, both molecular mechanisms of slow Axonal Transport and difference in usage of Kinesin‐1 between slow and Fast Axonal Transport have been elusive. Here, we show that slow Axonal Transport depends on the interaction between the DnaJ‐like domain of the kinesin light chain in the Kinesin‐1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin‐1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein Transport and reinforced membranous organelle Transport, indicating that this domain might have a function as a switchover system between slow and Fast Transport by Hsc70. Transgenic mice overexpressing a dominant‐negative form of the domain showed delayed slow Transport, accelerated Fast Transport and optic axonopathy. These findings provide a basis for the regulatory mechanism of intracellular Transport and its intriguing implication in neuronal dysfunction.
-
kinesin superfamily protein 3 kif3 motor Transports fodrin associating vesicles important for neurite building
Journal of Cell Biology, 2000Co-Authors: Sen Takeda, Sumio Terada, Daehyun Seog, Hiroto Yamazaki, Yoshimitsu Kanai, Nobutaka HirokawaAbstract:Kinesin superfamily proteins (KIFs) comprise several dozen molecular motor proteins. The KIF3 heterotrimer complex is one of the most abundantly and ubiquitously expressed KIFs in mammalian cells. To unveil the functions of KIF3, microinjection of function-blocking monovalent antibodies against KIF3 into cultured superior cervical ganglion (SCG) neurons was carried out. They significantly blocked Fast Axonal Transport and brought about inhibition of neurite extension. A yeast two-hybrid binding assay revealed the association of fodrin with the KIF3 motor through KAP3. This was further confirmed by using vesicles collected from large bundles of axons (cauda equina), from which membranous vesicles could be prepared in pure preparations. Both immunoprecipitation and immunoelectron microscopy indicated the colocalization of fodrin and KIF3 on the same vesicles, the results reinforcing the evidence that the cargo of the KIF3 motor consists of fodrin-associating vesicles. In addition, pulse-labeling study implied partial comigration of both molecules as Fast flow components. Taken together, the KIF3 motor is engaged in Fast Axonal Transport that conveys membranous components important for neurite extension.
Yuyu Song - One of the best experts on this subject based on the ideXlab platform.
-
prion protein inhibits Fast Axonal Transport through a mechanism involving casein kinase 2
PLOS ONE, 2017Co-Authors: Emiliano Zamponi, Yuyu Song, Fiamma Buratti, Gabriel Enrique Cataldi, Hector Hugo Caicedo, Lisa Jungbauer, Mary Jo Ladu, Mariano Bisbal, Alfredo Lorenzo, Pablo HelgueraAbstract:Prion diseases include a number of progressive neuropathies involving conformational changes in cellular prion protein (PrPc) that may be fatal sporadic, familial or infectious. Pathological evidence indicated that neurons affected in prion diseases follow a dying-back pattern of degeneration. However, specific cellular processes affected by PrPc that explain such a pattern have not yet been identified. Results from cell biological and pharmacological experiments in isolated squid axoplasm and primary cultured neurons reveal inhibition of Fast Axonal Transport (FAT) as a novel toxic effect elicited by PrPc. Pharmacological, biochemical and cell biological experiments further indicate this toxic effect involves casein kinase 2 (CK2) activation, providing a molecular basis for the toxic effect of PrPc on FAT. CK2 was found to phosphorylate and inhibit light chain subunits of the major motor protein conventional kinesin. Collectively, these findings suggest CK2 as a novel therapeutic target to prevent the gradual loss of neuronal connectivity that characterizes prion diseases.
-
hiv glycoprotein gp120 impairs Fast Axonal Transport by activating tak1 signaling pathways
Asn Neuro, 2016Co-Authors: Sarah Berth, Yuyu Song, Gerardo Morfini, Nichole A Mesnardhoaglin, Bin Wang, Hajwa Kim, Maria SaparAbstract:Sensory neuropathies are the most common neurological complication of HIV. Of these, distal sensory polyneuropathy (DSP) is directly caused by HIV infection and characterized by length-dependent Axonal degeneration of dorsal root ganglion (DRG) neurons. Mechanisms for Axonal degeneration in DSP remain unclear, but recent experiments revealed that the HIV glycoprotein gp120 is internalized and localized within axons of DRG neurons. Based on these findings, we investigated whether intra-Axonal gp120 might impair Fast Axonal Transport (FAT), a cellular process critical for appropriate maintenance of the Axonal compartment. Significantly, we found that gp120 severely impaired both anterograde and retrograde FAT. Providing a mechanistic basis for these effects, pharmacological experiments revealed an involvement of various phosphotransferases in this toxic effect, including members of mitogen-activated protein kinase pathways (Tak-1, p38, and c-Jun N-terminal Kinase (JNK)), inhibitor of kappa-B-kinase 2 (IKK2), and PP1. Biochemical experiments and Axonal outgrowth assays in cell lines and primary cultures extended these findings. Impairments in neurite outgrowth in DRG neurons by gp120 were rescued using a Tak-1 inhibitor, implicating a Tak-1 mitogen-activated protein kinase pathway in gp120 neurotoxicity. Taken together, these observations indicate that kinase-based impairments in FAT represent a novel mechanism underlying gp120 neurotoxicity consistent with the dying-back degeneration seen in DSP. Targeting gp120-based impairments in FAT with specific kinase inhibitors might provide a novel therapeutic strategy to prevent Axonal degeneration in DSP.
-
Fast Axonal Transport in isolated axoplasm from the squid giant axon
Methods in Cell Biology, 2016Co-Authors: Yuyu Song, Gerardo Morfini, Scott T. Brady, Minsu KangAbstract:Abstract The giant axon of the squid provides a unique cell biological model for analyzing the biochemistry and cell biology of the axon. These axons may exceed 500 μm in diameter and can be readily dissected. Once the surrounding small axons and connective tissue are removed, the axoplasm can be extruded as an intact cylinder of isolated cytoplasm. This isolated axoplasm is morphologically indistinguishable from the intact axon, but without permeability barriers. Fast Axonal Transport will continue for more than 4 h after extrusion and can be visualized in real time. By perfusing defined concentrations of proteins and/or reagents into the axoplasm, this preparation represents a powerful model for study of intracellular trafficking and its underlying molecular mechanisms.
-
the sphingolipid psychosine inhibits Fast Axonal Transport in krabbe disease by activation of gsk3β and deregulation of molecular motors
The Journal of Neuroscience, 2013Co-Authors: Ludovico Cantuti Castelvetri, Maria I Givogri, Amy K Hebert, Benjamin Smith, Yuyu Song, Agnieszka Kaminska, Aurora Lopezrosas, Gerardo Morfini, Gustavo Pigino, Mark S SandsAbstract:Loss of function of galactosylceramidase lysosomal activity causes demyelination and vulnerability of various neuronal populations in Krabbe disease. Psychosine, a lipid-raft-associated sphingolipid that accumulates in this disease, is thought to trigger these abnormalities. Myelin-free in vitro analyses showed that psychosine inhibited Fast Axonal Transport through the activation of Axonal PP1 and GSK3β in the axon. Abnormal levels of activated GSK3β and abnormally phosphorylated kinesin light chains were found in nerve samples from a mouse model of Krabbe disease. Administration of GSK3β inhibitors significantly ameliorated Transport defects in vitro and in vivo in peripheral axons of the mutant mouse. This study identifies psychosine as a pathogenic sphingolipid able to block Fast Axonal Transport and is the first to provide a molecular mechanism underlying dying-back degeneration in this genetic leukodystrophy.
-
inhibition of Fast Axonal Transport by pathogenic sod1 involves activation of p38 map kinase
PLOS ONE, 2013Co-Authors: Yuyu Song, Agnieszka Kaminska, Gerardo Morfini, Daryl A Bosco, Hannah E Brown, Rodolfo GattoAbstract:Dying-back degeneration of motor neuron axons represents an established feature of familial amyotrophic lateral sclerosis (FALS) associated with superoxide dismutase 1 (SOD1) mutations, but axon-autonomous effects of pathogenic SOD1 remained undefined. Characteristics of motor neurons affected in FALS include abnormal kinase activation, aberrant neurofilament phosphorylation, and Fast Axonal Transport (FAT) deficits, but functional relationships among these pathogenic events were unclear. Experiments in isolated squid axoplasm reveal that FALS-related SOD1 mutant polypeptides inhibit FAT through a mechanism involving a p38 mitogen activated protein kinase pathway. Mutant SOD1 activated neuronal p38 in mouse spinal cord, neuroblastoma cells and squid axoplasm. Active p38 MAP kinase phosphorylated kinesin-1, and this phosphorylation event inhibited kinesin-1. Finally, vesicle motility assays revealed previously unrecognized, isoform-specific effects of p38 on FAT. Axon-autonomous activation of the p38 pathway represents a novel gain of toxic function for FALS-linked SOD1 proteins consistent with the dying-back pattern of neurodegeneration characteristic of ALS.