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Sergio Grinstein - One of the best experts on this subject based on the ideXlab platform.

  • rab5 regulates macropinocytosis by recruiting the inositol 5 phosphatases ocrl and inpp5b that hydrolyse ptdins 4 5 p2
    Journal of Cell Science, 2021
    Co-Authors: Michelle E Maxson, Sergio Grinstein, Helen Sarantis, Allen Volchuk, John H Brumell
    Abstract:

    Rab5 is required for macropinosome formation, but its site and mode of action remain unknown. We report that Rab5 acts at the plasma membrane, downstream of ruffling, to promote macropinosome sealing and scission. Dominant-negative Rab5, which obliterates macropinocytosis, had no effect on the development of membrane ruffles. However, Rab5-containing vesicles were recruited to circular membrane ruffles, and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-dependent endomembrane fusion was necessary for the completion of macropinocytosis. This fusion event coincided with the disappearance of PtdIns(4,5)P2 that accompanies macropinosome closure. Counteracting the depletion of PtdIns(4,5)P2 by expression of phosphatidylinositol-4-phosphate 5-kinase impaired macropinosome formation. Importantly, we found that the removal of PtdIns(4,5)P2 is dependent on Rab5, through the Rab5-mediated recruitment of the inositol 5-phosphatases OCRL and Inpp5b, via APPL1. Knockdown of OCRL and Inpp5b, or APPL1, prevented macropinosome closure without affecting ruffling. We therefore propose that Rab5 is essential for the clearance of PtdIns(4,5)P2 needed to complete the scission of macropinosomes or to prevent their back-fusion with the plasmalemma.

  • rab5 regulates macropinosome closure through recruitment of the inositol 5 phosphatases ocrl inpp5b and the hydrolysis of ptdins 4 5 p2
    bioRxiv, 2020
    Co-Authors: Michelle E Maxson, Sergio Grinstein, Helen Sarantis, Allen Volchuk, John H Brumell
    Abstract:

    Abstract Rab5 is required for macropinosome formation, but its site and mode of action remain unknown. We report that Rab5 acts at the plasma membrane, downstream of ruffling, to promote macropinosome sealing and scission. Dominant-negative Rab5, which obliterates macropinocytosis, had no effect on the development of membrane ruffles. However, Rab5-containing vesicles were recruited to circular membrane ruffles, and SNARE-dependent endomembrane fusion was necessary for completion of macropinocytosis. This fusion event coincided with the disappearance of PtdIns(4,5)P2 that accompanies macropinosome closure. Counteracting the depletion of PtdIns(4,5)P2 by expression of phosphatidylinositol-4-phosphate 5-kinase impaired macropinosome formation. Importantly, we found that removal of PtdIns(4,5)P2 is dependent on Rab5, through the Rab5-mediated recruitment of the inositol 5-phosphatases OCRL and Inpp5b, via APPL1. Knockdown of OCRL and Inpp5b, or APPL1 prevented macropinosome closure, without affecting ruffling. We therefore propose that Rab5 is essential for the clearance of PtdIns(4,5)P2 needed to complete macropinosome scission from the plasmalemma.

  • rab5 regulates macropinosome closure by recruitment of ocrl inpp5b and hydrolysis of ptdins 4 5 p2
    bioRxiv, 2020
    Co-Authors: Sergio Grinstein, Helen Sarantis, Allen Volchuk, John H Brumell, Michelle E Maxson
    Abstract:

    AO_SCPLOWBSTRACTC_SCPLOWRab5 is required for macropinosome formation, but its site and mode of action remain unknown. We report that Rab5 acts at the plasma membrane, downstream of ruffling, to promote macropinosome sealing and scission. Dominant-negative Rab5, which obliterates macropinocytosis, had no effect on the development of membrane ruffles. However, Rab5-containing vesicles were recruited to circular membrane ruffles, and SNARE-dependent endomembrane fusion was necessary for completion of macropinocytosis. This fusion event coincided with the disappearance of PtdIns(4,5)P2 that accompanies macropinosome closure. Counteracting the depletion of PtdIns(4,5)P2 by expression of phosphatidylinositol-4-phosphate 5-kinase impaired macropinosome formation. Importantly, we found that removal of PtdIns(4,5)P2 is dependent on Rab5, through the Rab5-mediated recruitment of the inositol 5-phosphatases OCRL and Inpp5b, via APPL1. Knockdown of OCRL and Inpp5b, or APPL1 prevented macropinosome closure, without affecting ruffling. We therefore propose that Rab5 is essential for the clearance of PtdIns(4,5)P2 needed to complete macropinosome scission from the plasmalemma.

  • recruitment of ocrl and inpp5b to phagosomes by rab5 and appl1 depletes phosphoinositides and attenuates akt signaling
    Molecular Biology of the Cell, 2012
    Co-Authors: Michal Bohdanowicz, Daniel M Balkin, Sergio Grinstein
    Abstract:

    Sealing of phagosomes is accompanied by the disappearance of phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P2) from their cytoplasmic leaflet. Elimination of PtdIns(4,5)P2, which is required for actin remodeling during phagosome formation, has been attributed to hydrolysis by phospholipase C and phosphorylation by phosphatidylinositol 3-kinase. We found that two inositol 5-phosphatases, OCRL and Inpp5B, become associated with nascent phagosomes. Both phosphatases, which are Rab5 effectors, associate with the adaptor protein APPL1, which is recruited to the phagosomes by active Rab5. Knockdown of APPL1 or inhibition of Rab5 impairs association of OCRL and Inpp5B with phagosomes and prolongs the presence of PtdIns(4,5)P2 and actin on their membranes. Even though APPL1 can serve as an anchor for Akt, its depletion accentuated the activation of the kinase, likely by increasing the amount of PtdIns(4,5)P2 available to generate phosphatidylinositol (3,4,5)-trisphosphate. Thus, inositol 5-phosphatases are important contributors to the phosphoinositide remodeling and signaling that are pivotal for phagocytosis.

  • class i and class iii phosphoinositide 3 kinases are required for actin polymerization that propels phagosomes
    Journal of Cell Biology, 2010
    Co-Authors: Michal Bohdanowicz, Gabriela Cosio, Jonathan M Backer, Sergio Grinstein
    Abstract:

    Actin polymerization drives the extension of pseudopods that trap and engulf phagocytic targets. The polymerized actin subsequently dissociates as the phagocytic vacuole seals and detaches from the plasma membrane. We found that phagosomes formed by engagement of integrins that serve as complement receptors (CR3) undergo secondary waves of actin polymerization, leading to the formation of “comet tails” that propel the vacuoles inside the cells. Actin tail formation was accompanied by and required de novo formation of PI(3,4)P2 and PI(3,4,5)P3 on the phagosomal membrane by class I phosphoinositide 3-kinases (PI3Ks). Although the phosphatidylinositide phosphatase Inpp5B was recruited to nascent phagosomes, it rapidly detached from the membrane after phagosomes sealed. Detachment of Inpp5B required the formation of PI(3)P. Thus, class III PI3K activity was also required for the accumulation of PI(4,5)P2 and PI(3,4,5)P3 and for actin tail formation. These experiments reveal a new PI(3)P-sensitive pathway leading to PI(3,4)P2 and PI(3,4,5)P3 formation and signaling in endomembranes.

Robert L Nussbaum - One of the best experts on this subject based on the ideXlab platform.

  • kidney tubular ablation of ocrl inpp5b phenocopies lowe syndrome tubulopathy
    Journal of The American Society of Nephrology, 2017
    Co-Authors: Kazunori Inoue, Ramiro Nandez, Daniel M Balkin, Robert L Nussbaum, Lijuan Liu, Xuefei Tian, Tong Wang
    Abstract:

    Lowe syndrome and Dent disease are two conditions that result from mutations of the inositol 5-phosphatase oculocerebrorenal syndrome of Lowe (OCRL) and share the feature of impaired kidney proximal tubule function. Genetic ablation of Ocrl in mice failed to recapitulate the human phenotypes, possibly because of the redundant functions of OCRL and its paralog type 2 inositol polyphosphate-5-phosphatase (INPP5B). Germline knockout of both paralogs in mice results in early embryonic lethality. We report that kidney tubule-specific inactivation of Inpp5b on a global Ocrl-knockout mouse background resulted in low molecular weight proteinuria, phosphaturia, and acidemia. At the cellular level, we observed a striking impairment of clathrin-dependent and -independent endocytosis in proximal tubules, phenocopying what has been reported for Dent disease caused by mutations in the gene encoding endosomal proton-chloride exchange transporter 5. These results suggest that the functions of OCRL/INPP5B and proton-chloride exchange transporter 5 converge on shared mechanisms, the impairment of which has a dramatic effect on proximal tubule endocytosis.

  • mouse model for lowe syndrome dent disease 2 renal tubulopathy
    Journal of The American Society of Nephrology, 2011
    Co-Authors: Susan P Bothwell, Emily Chan, Isa Bernardini, William A. Gahl, Robert L Nussbaum
    Abstract:

    The Lowe oculocerebrorenal syndrome is an X-linked disorder characterized by congenital cataracts, cognitive disability, and proximal tubular dysfunction. Both this syndrome and Dent Disease 2 result from loss-of-function mutations in the OCRL gene, which encodes a type II phosphatidylinositol bisphosphate 5-phosphatase. Ocrl-deficient mice are unaffected, however, which we believe reflects a difference in how humans and mice cope with the enzyme deficiency. Inpp5b and INPP5B, paralogous autosomal genes that encode another type II phosphoinositide 5-phosphatase in mice and humans, respectively, might explain the distinct phenotype in the two species because they are the closest paralogs to Ocrl and OCRL in their respective genomes yet differ between the two species with regard to expression and splicing. Here, we generated Ocrl(-/-) mice that express INPP5B but not Inpp5b. Similar to the human syndromes, all showed reduced postnatal growth, low molecular weight proteinuria, and aminoaciduria. Thus, we created an animal model for OCRL and Dent Disease 2 tubulopathy by humanizing a modifier paralog in mice already carrying the mutant disease gene.

  • Species-specific difference in expression and splice-site choice in Inpp5b, an inositol polyphosphate 5-phosphatase paralogous to the enzyme deficient in Lowe Syndrome
    Mammalian Genome, 2010
    Co-Authors: Susan P Bothwell, Leslie W. Farber, Adam Hoagland, Robert L Nussbaum
    Abstract:

    The oculocerebrorenal syndrome of Lowe (OCRL; MIM #309000) is an X-linked human disorder characterized by congenital cataracts, mental retardation, and renal proximal tubular dysfunction caused by loss-of-function mutations in the OCRL gene that encodes Ocrl, a type II phosphatidylinositol bisphosphate (PtdIns4,5P_2) 5-phosphatase. In contrast, mice with complete loss-of-function of the highly homologous ortholog Ocrl have no detectable renal, ophthalmological, or central nervous system abnormalities. We inferred that the disparate phenotype between Ocrl-deficient humans and mice was likely due to differences in how the two species compensate for loss of the Ocrl enzyme. We therefore turned our attention to Inpp5b, another type II PtdIns4,5P_2 5-phosphatase encoded by Inpp5b in mice and INPP5B in humans, as potential compensating genes in the two species, because Inpp5b / INPP5B are the most highly conserved paralogs to Ocrl / OCRL in the respective genomes of both species and Inpp5b demonstrates functional overlap with Ocrl in mice in vivo . We used in silico sequence analysis, reverse-transcription PCR, quantitative PCR, and transient transfection assays of promoter function to define splice-site usage and the function of an internal promoter in mouse Inpp5b versus human INPP5B . We found mouse Inpp5b and human INPP5B differ in their transcription, splicing, and primary amino acid sequence. These observations form the foundation for analyzing the functional basis for the difference in how Inpp5b and INPP5B compensate for loss of Ocrl function and, by providing insight into the cellular roles of Ocrl and Inpp5b, aid in the development of a model system in which to study Lowe syndrome.

  • x inactivation analysis of embryonic lethality in ocrl wt inpp5b mice
    Mammalian Genome, 2010
    Co-Authors: David J. Bernard, Robert L Nussbaum
    Abstract:

    Mutations in the human OCRL gene, which encodes a phosphatidylinositol(4,5)bisphosphate 5-phosphatase, result in the X-linked oculocerebrorenal syndrome of Lowe. Mice with a targeted disruption of Ocrl have no phenotypic abnormalities. Targeted disruption of its closest paralog, Inpp5b, causes male infertility in the 129S6 background. Mice with disruptions of both genes are lost in utero prior to 9.5-10.5 dpc, indicating that there is a functional overlap between the two paralogs early in development. We analyzed the pattern of X-inactivation in four tissues of distinct embryonic origin from Ocrlwt/−;Inpp5b−/− females to explore the timing and tissue distribution of the functional overlap. X-inactivation was strongly skewed against the disrupted Ocrl− allele being on the active X chromosome in all four tissues tested, indicating that there is early selection against cell lineages lacking both Ocrl and Inpp5b. Extraembryonic tissue was also involved in the lethality because there were never any live-born Ocrlwt/−;Inpp5b−/− females when the functional Ocrlwt allele was on the paternal X chromosome, which is preferentially inactivated in trophoblast-derived extraembryonic tissues. Live-born Ocrlwt/−;Inpp5b−/− females were found when the functional Ocrlwt allele was maternal, although in fewer numbers than expected. The importance of the extraembryonic tissues in the early embryonic lethality of embryos lacking both Ocrl and Inpp5b is reinforced by the successful isolation of a viable 40,XX Ocrl−/−;Inpp5b−/− embryonic stem cell from the inner cell mass of a 3.5-dpc blastocyst prior to implantation. These results indicate a functional overlap of Ocrl and Inpp5b in most cell lineages, especially in extraembryonic tissues.

  • disrupted sperm function and fertilin β processing in mice deficient in the inositol polyphosphate 5 phosphatase inpp5b
    Developmental Biology, 2001
    Co-Authors: Elina Hellsten, Pasi A. Jänne, David J. Bernard, Janice Perry Evans, Robert L Nussbaum
    Abstract:

    Inpp5b is an ubiquitously expressed type II inositol polyphosphate 5-phosphatase. We have disrupted the Inpp5b gene in mice and found that homozygous mutant males are infertile. Here we examine the causes for the infertility in detail. We demonstrate that sperm from Inpp5b(-/-) males have reduced motility and reduced ability to fertilize eggs, although capacitation and acrosome exocytosis appear to be normal. In addition, fertilin beta, a sperm surface protein involved in sperm-egg membrane interactions that is normally proteolytically processed during sperm transit through the epididymis, showed reduced levels of processing in the Inpp5b(-/-) animals. Inpp5b was expressed in the Sertoli cells and epididymis and at low levels in the developing germ cells; however, mice lacking Inpp5b in spermatids and not in other cell types generated by conditional gene targeting, were fully fertile. The abnormalities in mutant sperm function and maturation appear to arise from defects in the functioning of Sertoli and epididymal epithelial cells. Our results directly demonstrate a previously unknown role for phosphoinositides in normal sperm maturation beyond their previously characterized involvement in the acrosome reaction. Inpp5b(-/-) mice provide an excellent model to study the role of Sertoli and epididymal epithelial cells in the differentiation and maturation of sperm.

Christina Anne Mitchell - One of the best experts on this subject based on the ideXlab platform.

  • deletion of the phosphatase inpp5e in the murine retina impairs photoreceptor axoneme formation and prevents disc morphogenesis
    Journal of Biological Chemistry, 2021
    Co-Authors: Ali Sharif, Christina Anne Mitchell, Cecilia D Gerstner, Martha A Cady, Vadim Y Arshavsky, Guoxin Ying, Jeanne M Frederick, Wolfgang Baehr
    Abstract:

    INPP5E, also known as pharbin, is a ubiquitously expressed phosphatidylinositol polyphosphate 5-phosphatase that is typically located in the primary cilia and modulates the phosphoinositide composition of membranes. Mutations to or loss of INPP5E is associated with ciliary dysfunction. INPP5E missense mutations of the phosphatase catalytic domain cause Joubert syndrome in humans—a syndromic ciliopathy affecting multiple tissues including the brain, liver, kidney, and retina. In contrast to other primary cilia, photoreceptor INPP5E is prominently expressed in the inner segment and connecting cilium and absent in the outer segment, which is a modified primary cilium dedicated to phototransduction. To investigate how loss of INPP5e causes retina degeneration, we generated mice with a retina-specific KO (Inpp5eF/F;Six3Cre, abbreviated as retInpp5e−/−). These mice exhibit a rapidly progressing rod–cone degeneration resembling Leber congenital amaurosis that is nearly completed by postnatal day 21 (P21) in the central retina. Mutant cone outer segments contain vesicles instead of discs as early as P8. Although P10 mutant outer segments contain structural and phototransduction proteins, axonemal structure and disc membranes fail to form. Connecting cilia of retInpp5e−/− rods display accumulation of intraflagellar transport particles A and B at their distal ends, suggesting disrupted intraflagellar transport. Although INPP5E ablation may not prevent delivery of outer segment–specific proteins by means of the photoreceptor secretory pathway, its absence prevents the assembly of axonemal and disc components. Herein, we suggest a model for INPP5E–Leber congenital amaurosis, proposing how deletion of INPP5E may interrupt axoneme extension and disc membrane elaboration.

  • deletion of inpp5e in the murine retina impairs axoneme formation and prevents photoreceptor disc morphogenesis
    bioRxiv, 2020
    Co-Authors: Ali Sharif, Christina Anne Mitchell, Cecilia D Gerstner, Martha A Cady, Vadim Y Arshavsky, Guoxin Ying, Jeanne M Frederick, Wolfgang Baehr
    Abstract:

    INPP5E (pharbin) is a ubiquitously-expressed, farnesylated phosphatidylinositol polyphosphate 5-phosphatase which modulates the phosphoinositide composition of membranes. INPP5E resides in primary cilia, and mutations or loss of INPP5E are associated with ciliary dysfunction. INPP5E missense mutations of the phosphatase catalytic domain cause Joubert syndrome in humans, a syndromic ciliopathy affecting multiple tissues including brain, liver, kidney and retina. We show that, differing from other primary cilia, INPP5E is present in the wildtype photoreceptor inner segment and absent in the outer segment--a modified primary cilium dedicated to phototransduction. We generated Inpp5eF/F;Six3Cre (in short, retInpp5e-/-) mice which exhibit a rapidly progressing rod-cone degeneration nearly completed by postnatal day 21 (P21) in the central retina. Mutant cone outer segments contain vesicles instead of discs as early as P8. While P10 mutant outer segments contain phototransduction and structural proteins, they do not form axonemes and fail to elaborate disc membranes. Connecting cilia of retInpp5e-/- rods appear normal, although IFT-B/A particles accumulate at their distal ends suggesting disrupted intraflagellar transport. These results show that ablation of INPP5E does not impair the secretory pathway responsible for delivery of outer segment-specific proteins, but blocks axonemal extension and prevents disc morphogenesis.

  • regulation of ptdins 3 4 5 p3 akt signalling by inositol polyphosphate 5 phosphatases
    Biochemical Society Transactions, 2016
    Co-Authors: Matthew J Eramo, Christina Anne Mitchell
    Abstract:

    The phosphoinositide 3-kinase (PI3K) generated lipid signals, PtdIns(3,4,5) P 3 and PtdIns(3,4) P 2, are both required for the maximal activation of the serine/threonine kinase proto-oncogene Akt. The inositol polyphosphate 5-phosphatases (5-phosphatases) hydrolyse the 5-position phosphate from the inositol head group of PtdIns(3,4,5) P 3 to yield PtdIns(3,4) P 2. Extensive work has revealed several 5-phosphatases inhibit PI3K-driven Akt signalling, by decreasing PtdIns(3,4,5) P 3 despite increasing cellular levels of PtdIns(3,4) P 2. The roles that 5-phosphatases play in suppressing cell proliferation and transformation are slow to emerge; however, the 5-phosphatase PIPP [proline-rich inositol polyphosphate 5-phosphatase; inositol polyphosphate 5-phosphatase ( INPP5J )] has recently been identified as a putative tumour suppressor in melanoma and breast cancer and SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase 1] inhibits haematopoietic cell proliferation. INPP5E regulates cilia stability and INPP5E mutations have been implicated ciliopathy syndromes. This review will examine 5-phosphatase regulation of PI3K/Akt signalling, focussing on the role PtdIns(3,4,5) P 3 5-phosphatases play in developmental diseases and cancer. * 3AC, : 3-a-aminocholestane; 5-phosphatases, : inositol polyphosphate 5-phosphatases; AURKA, : aurora kinase A; BJAB, : human B-cell lymphoma cell line; BMMC, : bone marrow-derived mast cells; CHO, : Chinese hamster ovary; EGF, : epidermal growth factor; ENU, : N -ethyl- N -nitrosourea; ER, : estrogen receptor; FoxO, : forkhead box, class O; GLUT4, : glucose transporter type 4; Gpr161, : G-protein-coupled receptor 161; HEK, : human embryonic kidney; IGF-1, : insulin-like growth factor-1; IL-3, : interleukin-3; LPS, : lipopolysaccharide; MEF, : mouse embryonic fibroblast; MM, : multiple myeloma; mTORC, : mammalian target of rapamycin complex; NFAT, : nuclear factor of activated T cells; OCRL, : oculocerebrorenal syndrome of Lowe; Pak1, : P21-activated kinase 1; PDK1, : phosphoinositide-dependent kinase 1; PH, : pleckstrin homology; 1PIE, : (2-phenyl-benzo[ h ]quinolin-4-yl)-[2]piperidyl-methanol hydrochloride; 2PIQ, : 1-[(chlorophenyl)methyl]-2-methyl-5-(methylthio)-1H-indole-3-ethanamine hydrochloride; 6PTQ, : (2-adamantan-1-yl-6,8-dichloro-quinolin-4-yl)-pyridin-2-yl-methanol hydrochloride; PI3K, : phosphoinositide 3-kinase; PIPP, : proline-rich inositol polyphosphate 5-phosphatase; PRAS40, : proline-rich Akt substrate of 40 kDa; PTEN, : phosphatase and tensin homologue deleted on chromosome 10; PyMT, : polyoma middle T; Rheb, : Ras homologue enriched in brain; RhoGAP, : Rho GTP-ase activating protein; SAG, : smoothened agonist; Shh, : sonic hedgehog; SHIP, : SH2-containing inositol phosphatase; SKICH, : SKIP carboxy homology; SKIP, : skeletal muscle- and kidney-enriched inositol phosphatase; TNFα, : tumour necrosis factor α; TSC, : tuberous sclerosis; TULP3, : Tubby-like protein 3

  • inpp5e interacts with aurka linking phosphoinositide signaling to primary cilium stability
    Journal of Cell Science, 2015
    Co-Authors: Olga V Plotnikova, Christina Anne Mitchell, Jennifer M Dyson, Sandra Hakim, Sarah E Conduit, Seongjin Seo, Denny L Cottle, Ian M Smyth
    Abstract:

    Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) cause the ciliopathies known as Joubert and MORM syndromes; however, the role of INPP5E in ciliary biology is not well understood. Here, we describe an interaction between INPP5E and AURKA, a centrosomal kinase that regulates mitosis and ciliary disassembly, and we show that this interaction is important for the stability of primary cilia. Furthermore, AURKA phosphorylates INPP5E and thereby increases its 5-phosphatase activity, which in turn promotes transcriptional downregulation of AURKA, partly through an AKT-dependent mechanism. These findings establish the first direct link between AURKA and phosphoinositide signaling and suggest that the function of INPP5E in cilia is at least partly mediated by its interactions with AURKA.

  • Inositol polyphosphate 5-phosphatases; new players in the regulation of cilia and ciliopathies
    FEBS Letters, 2012
    Co-Authors: Sarah E Conduit, Jennifer M Dyson, Christina Anne Mitchell
    Abstract:

    Phosphoinositides regulate numerous cellular events via the recruitment and activation of multiple lipid-binding effector proteins. The precise temporal and spatial regulation of phosphoinositide signals by the co-ordinated activities of phosphoinositide kinases and phosphatases is essential for homeostasis and development. Mutations in two inositol polyphosphate 5-phosphatases, INPP5E and OCRL, cause the cerebrorenal syndromes of Joubert and Lowe's, respectively. INPP5E and OCRL exhibit overlapping phosphoinositide substrate specificity and subcellular localisation, including an association with the primary cilia. Here, we review recent studies that identify a new role for these enzymes in the regulation of primary cilia function. Joubert syndrome has been extensively linked to primary cilia defects, and Lowe's may represent a new class of 'ciliopathy associated' syndromes.

Serge N Schiffmann - One of the best experts on this subject based on the ideXlab platform.

  • Modulation of Ciliary Phosphoinositide Content Regulates Trafficking and Sonic Hedgehog Signaling Output
    Developmental cell, 2015
    Co-Authors: Marcelo Chávez, Stephane Schurmans, Sabrina Ena, Jacqueline Van Sande, Alban De Kerchove D'exaerde, Serge N Schiffmann
    Abstract:

    Ciliary transport is required for ciliogenesis, signal transduction, and trafficking of receptors to the primary cilium. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) have been associated with ciliary dysfunction; however, its role in regulating ciliary phosphoinositides is unknown. Here we report that in neural stem cells, phosphatidylinositol 4-phosphate (PI4P) is found in high levels in cilia whereas phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) is not detectable. Upon INPP5E inactivation, PI(4,5)P2 accumulates at the ciliary tip whereas PI4P is depleted. This is accompanied by recruitment of the PI(4,5)P2-interacting protein TULP3 to the ciliary membrane, along with Gpr161. This results in an increased production of cAMP and a repression of the Shh transcription gene Gli1. Our results reveal the link between ciliary regulation of phosphoinositides by INPP5E and Shh regulation via ciliary trafficking of TULP3/Gpr161 and also provide mechanistic insight into ciliary alterations found in Joubert and MORM syndromes resulting from INPP5E mutations.

  • inpp5e mutations cause primary cilium signaling defects ciliary instability and ciliopathies in human and mouse
    Nature Genetics, 2009
    Co-Authors: Monique Jacoby, James J Cox, Stephanie Gayral, Daniel J Hampshire, Mohammed Ayub, Marianne Blockmans, Eileen Pernot, Marina V Kisseleva, Philippe Compere, Serge N Schiffmann
    Abstract:

    The primary cilium is an antenna-like structure that protrudes from the cell surface of quiescent/differentiated cells and participates in extracellular signal processing. Here, we report that mice deficient for the lipid 5-phosphatase Inpp5e develop a multiorgan disorder associated with structural defects of the primary cilium. In ciliated mouse embryonic fibroblasts, Inpp5e is concentrated in the axoneme of the primary cilium. Inpp5e inactivation did not impair ciliary assembly but altered the stability of pre-established cilia after serum addition. Blocking phosphoinositide 3-kinase (PI3K) activity or ciliary platelet-derived growth factor receptor alpha (PDGFRalpha) restored ciliary stability. In human INPP5E, we identified a mutation affecting INPP5E ciliary localization and cilium stability in a family with MORM syndrome, a condition related to Bardet-Biedl syndrome. Together, our results show that INPP5E plays an essential role in the primary cilium by controlling ciliary growth factor and PI3K signaling and stability, and highlight the consequences of INPP5E dysfunction.

Stephane Schurmans - One of the best experts on this subject based on the ideXlab platform.

  • the phosphoinositide 5 phosphatase inpp5k from gene structure to in vivo functions
    Advances in biological regulation, 2021
    Co-Authors: Stephane Schurmans, Charlesandrew Vande Catsyne, Christophe Desmet, Bastien Moes
    Abstract:

    Abstract INPP5K (Inositol Polyphosphate 5-Phosphatase K, or SKIP (for Skeletal muscle and Kidney enriched Inositol Phosphatase) is a member of the phosphoinositide 5-phosphatases family. Its protein structure is comprised of a N-terminal catalytic domain which hydrolyses both PtdIns(4,5)P2 and PtdIns(3,4,5)P3, followed by a SKICH domain at the C-terminus which is responsible for protein-protein interactions and subcellular localization of INPP5K. Strikingly, INPP5K is mostly concentrated in the endoplasmic reticulum, although it is also detected at the plasma membrane, in the cytosol and the nucleus. Recently, mutations in INPP5K have been detected in patients with a rare form of autosomal recessive congenital muscular dystrophy with cataract, short stature and intellectual disability. INPP5K functions extend from control of insulin signaling, endoplasmic reticulum stress response and structural integrity, myoblast differentiation, cytoskeleton organization, cell adhesion and migration, renal osmoregulation, to cancer. The goal of this review is thus to summarize and comment recent and less recent data in the literature on INPP5K, in particular on the structure, expression, intracellular localization, interactions and functions of this specific member of the 5-phosphatases family.

  • phosphoinositides regulate ciliary protein trafficking to modulate hedgehog signaling
    Developmental Cell, 2015
    Co-Authors: Francesc R Garciagonzalo, Siew Cheng Phua, Elle C Roberson, Galo Garcia, Monika Abedin, Stephane Schurmans, Takanari Inoue, Jeremy F Reiter
    Abstract:

    Primary cilia interpret vertebrate Hedgehog (Hh) signals. Why cilia are essential for signaling is unclear. One possibility is that some forms of signaling require a distinct membrane lipid composition, found at cilia. We found that the ciliary membrane contains a particular phosphoinositide, PI(4)P, whereas a different phosphoinositide, PI(4,5)P2, is restricted to the membrane of the ciliary base. This distribution is created by Inpp5e, a ciliary phosphoinositide 5-phosphatase. Without Inpp5e, ciliary PI(4,5)P2 levels are elevated and Hh signaling is disrupted. Inpp5e limits the ciliary levels of inhibitors of Hh signaling, including Gpr161 and the PI(4,5)P2-binding protein Tulp3. Increasing ciliary PI(4,5)P2 levels or conferring the ability to bind PI(4)P on Tulp3 increases the ciliary localization of Tulp3. Lowering Tulp3 in cells lacking Inpp5e reduces ciliary Gpr161 levels and restores Hh signaling. Therefore, Inpp5e regulates ciliary membrane phosphoinositide composition, and Tulp3 reads out ciliary phosphoinositides to control ciliary protein localization, enabling Hh signaling.

  • Modulation of Ciliary Phosphoinositide Content Regulates Trafficking and Sonic Hedgehog Signaling Output
    Developmental cell, 2015
    Co-Authors: Marcelo Chávez, Stephane Schurmans, Sabrina Ena, Jacqueline Van Sande, Alban De Kerchove D'exaerde, Serge N Schiffmann
    Abstract:

    Ciliary transport is required for ciliogenesis, signal transduction, and trafficking of receptors to the primary cilium. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) have been associated with ciliary dysfunction; however, its role in regulating ciliary phosphoinositides is unknown. Here we report that in neural stem cells, phosphatidylinositol 4-phosphate (PI4P) is found in high levels in cilia whereas phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) is not detectable. Upon INPP5E inactivation, PI(4,5)P2 accumulates at the ciliary tip whereas PI4P is depleted. This is accompanied by recruitment of the PI(4,5)P2-interacting protein TULP3 to the ciliary membrane, along with Gpr161. This results in an increased production of cAMP and a repression of the Shh transcription gene Gli1. Our results reveal the link between ciliary regulation of phosphoinositides by INPP5E and Shh regulation via ciliary trafficking of TULP3/Gpr161 and also provide mechanistic insight into ciliary alterations found in Joubert and MORM syndromes resulting from INPP5E mutations.