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Thomas M. Roberts - One of the best experts on this subject based on the ideXlab platform.
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Major Sperm Protein and Sperm Locomotion
Encyclopedia of Biological Chemistry, 2013Co-Authors: K. Shimabukuro, Thomas M. RobertsAbstract:Major Sperm Protein (MSP) is a 14-kDa, multifunctional, Sperm-specific polypeptide that is essential for reproduction in nematodes. MSP polymerizes to form the filament meshworks that power Sperm movement and, remarkably, also functions as an extracellular signaling molecule that promotes oocyte maturation and fertilization. Nematode Sperm have no flagellum and, instead, extend a lamellipod to crawl over substrates like an amoeba. These cells lack actin, the key motility Protein in conventional crawling cells, and base their motility on MSP. The polymerization of MSP into filaments causes the leading edge membrane to protrude while the disassembly of MSP filament meshworks at the base of the lamellipod is involved in creating a force to pull the rear part of the Sperm forward. The tight coupling of these two forces in the Sperm necessitates finely tuned control of the cytoskeleton that is provided by a series of accessory Proteins, many of which are regulated by phosphorylation. While MSP works as an engine to propel Sperm movement, it also functions as a signaling molecule that, following its release from Sperm, diffuses through the reproductive tract to trigger the final steps of oocyte maturation and the movement of oocytes through the oviduct to the site of fertilization.
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Role of Major Sperm Protein (MSP) in the protrusion and retraction of Ascaris Sperm.
International review of cell and molecular biology, 2012Co-Authors: Thomas M. Roberts, Murray StewartAbstract:Nematode Sperm offer a unique perspective for investigating amoeboid cell motility. These cells display the hallmark features of amoeboid movement but power their locomotion with a cytoskeleton composed of Major Sperm Protein (MSP) filaments in place of the familiar actin cytoskeleton found in other crawling cells. Thus, properties of Sperm can be compared to those of actin-rich cells to identify the shared features that are essential to motility. Sperm are simple cells in which cytoskeletal dynamics are tightly coupled to protrusion of the leading edge and retraction of the cell body. These features have facilitated reconstitution of both protrusion and retraction in cell-free extracts and enabled identification of accessory components in the motility apparatus as well as elucidation of the mechanical basis of movement. Six MSP accessory Proteins have been isolated including four components of the Sperm cytoskeleton and two enzymes that play key roles in regulating cytoskeletal dynamics and locomotion. Analysis of this versatile in vitro motility system has identified motor-independent mechanisms for protrusion and retraction that are based on changes in filament-packing density. These changes result in expansion and contraction of the MSP-filament network that generate the forces for movement. We discuss how the mechanisms of motility that operate in nematode Sperm may contribute generally to the movement of crawling cells.
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Dephosphorylation of Major Sperm Protein (MSP) fiber Protein 3 by Protein phosphatase 2A during cell body retraction in the MSP-based amoeboid motility of Ascaris Sperm.
Molecular biology of the cell, 2009Co-Authors: Xu Wang, Murray Stewart, Mark R. Emmett, Alan G. Marshall, Thomas M. RobertsAbstract:The crawling movement of nematode Sperm requires coordination of leading edge protrusion with cell body retraction, both of which are powered by modulation of a cytoskeleton based on Major Sperm Protein (MSP) filaments. We used a cell-free in vitro motility system in which both protrusion and retraction can be reconstituted, to identify two Proteins involved in cell body retraction. Pharmacological and depletion-add back assays showed that retraction was triggered by a putative Protein phosphatase 2A (PP2A, a Ser/Thr phosphatase activated by tyrosine dephosphorylation). Immunofluorescence showed that PP2A was present in the cell body and was concentrated at the base of the lamellipod where the force for retraction is generated. PP2A targeted MSP fiber Protein 3 (MFP3), a Protein unique to nematode Sperm that binds to the MSP filaments in the motility apparatus. Dephosphorylation of MFP3 caused its release from the cytoskeleton and generated filament disassembly. Our results suggest that interaction between PP2A and MFP3 leads to local disassembly of the MSP cytoskeleton at the base of the lamellipod in Sperm that in turn pulls the trailing cell body forward.
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The role of filament-packing dynamics in powering amoeboid cell motility
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Long Miao, Murray Stewart, Orion Vanderlinde, Jun Liu, Richard P. Grant, Alan Wouterse, Katsuya Shimabukuro, Albert P. Philipse, Thomas M. RobertsAbstract:Although several models have been proposed to account for how cytoskeleton polymerization drives protrusion in cell motility, the precise mechanism remains controversial. Here, we show that, in addition to force exerted directly against the membrane by growing filaments, the way elongating filaments pack also contributes to protrusion by generating an expansion of the cytoskeleton gel. Tomography shows that filament packing in the Major Sperm Protein (MSP) -based nematode Sperm-motility machinery resembles that observed with rigid rods. Maximum rod-packing density decreases dramatically as the rods lengthen. Therefore, as filaments elongate, the cytoskeleton gel expands to accommodate their packing less densely. This volume expansion combines with polymerization to drive protrusion. Consistent with this hypothesis, an engineered MSP mutant that generates shorter filaments shows higher filament-packing density and slower movement.
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a ser thr kinase required for membrane associated assembly of the Major Sperm Protein motility apparatus in the amoeboid Sperm of ascaris
Molecular Biology of the Cell, 2007Co-Authors: Shawnna M. Buttery, Murray Stewart, Thomas M. RobertsAbstract:Leading edge protrusion in the amoeboid Sperm of Ascaris suum is driven by the localized assembly of the Major Sperm Protein (MSP) cytoskeleton in the same way that actin assembly powers protrusion in other types of crawling cell. Reconstitution of this process in vitro led to the identification of two accessory Proteins required for MSP polymerization: an integral membrane phosphoProtein, MSP polymerization-organizing Protein (MPOP), and a cytosolic component, MSP fiber Protein 2 (MFP2). Here, we identify and characterize a 34-kDa cytosolic Protein, MSP polymerization-activating kinase (MPAK) that links the activities of MPOP and MFP2. Depletion/add-back assays of Sperm extracts showed that MPAK, which is a member of the casein kinase 1 family of Ser/Thr Protein kinases, is required for motility. MPOP and MPAK comigrated by native gel electrophoresis, coimmunoprecipitated, and colocalized by immunofluorescence, indicating that MPOP binds to and recruits MPAK to the membrane surface. MPAK, in turn, phosphorylated MFP2 on threonine residues, resulting in incorporation of MFP2 into the cytoskeleton. Beads coated with MPAK assembled a surrounding cloud of MSP filaments when incubated in MPAK-depleted Sperm extract, but only when supplemented with detergent-solubilized MPOP. Our results suggest that interactions involving MPOP, MPAK, and MFP2 focus MSP polymerization to the plasma membrane at the leading edge of the cell thereby generating protrusion and minimizing nonproductive filament formation elsewhere.
Murray Stewart - One of the best experts on this subject based on the ideXlab platform.
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Role of Major Sperm Protein (MSP) in the protrusion and retraction of Ascaris Sperm.
International review of cell and molecular biology, 2012Co-Authors: Thomas M. Roberts, Murray StewartAbstract:Nematode Sperm offer a unique perspective for investigating amoeboid cell motility. These cells display the hallmark features of amoeboid movement but power their locomotion with a cytoskeleton composed of Major Sperm Protein (MSP) filaments in place of the familiar actin cytoskeleton found in other crawling cells. Thus, properties of Sperm can be compared to those of actin-rich cells to identify the shared features that are essential to motility. Sperm are simple cells in which cytoskeletal dynamics are tightly coupled to protrusion of the leading edge and retraction of the cell body. These features have facilitated reconstitution of both protrusion and retraction in cell-free extracts and enabled identification of accessory components in the motility apparatus as well as elucidation of the mechanical basis of movement. Six MSP accessory Proteins have been isolated including four components of the Sperm cytoskeleton and two enzymes that play key roles in regulating cytoskeletal dynamics and locomotion. Analysis of this versatile in vitro motility system has identified motor-independent mechanisms for protrusion and retraction that are based on changes in filament-packing density. These changes result in expansion and contraction of the MSP-filament network that generate the forces for movement. We discuss how the mechanisms of motility that operate in nematode Sperm may contribute generally to the movement of crawling cells.
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Dephosphorylation of Major Sperm Protein (MSP) fiber Protein 3 by Protein phosphatase 2A during cell body retraction in the MSP-based amoeboid motility of Ascaris Sperm.
Molecular biology of the cell, 2009Co-Authors: Xu Wang, Murray Stewart, Mark R. Emmett, Alan G. Marshall, Thomas M. RobertsAbstract:The crawling movement of nematode Sperm requires coordination of leading edge protrusion with cell body retraction, both of which are powered by modulation of a cytoskeleton based on Major Sperm Protein (MSP) filaments. We used a cell-free in vitro motility system in which both protrusion and retraction can be reconstituted, to identify two Proteins involved in cell body retraction. Pharmacological and depletion-add back assays showed that retraction was triggered by a putative Protein phosphatase 2A (PP2A, a Ser/Thr phosphatase activated by tyrosine dephosphorylation). Immunofluorescence showed that PP2A was present in the cell body and was concentrated at the base of the lamellipod where the force for retraction is generated. PP2A targeted MSP fiber Protein 3 (MFP3), a Protein unique to nematode Sperm that binds to the MSP filaments in the motility apparatus. Dephosphorylation of MFP3 caused its release from the cytoskeleton and generated filament disassembly. Our results suggest that interaction between PP2A and MFP3 leads to local disassembly of the MSP cytoskeleton at the base of the lamellipod in Sperm that in turn pulls the trailing cell body forward.
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The role of filament-packing dynamics in powering amoeboid cell motility
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Long Miao, Murray Stewart, Orion Vanderlinde, Jun Liu, Richard P. Grant, Alan Wouterse, Katsuya Shimabukuro, Albert P. Philipse, Thomas M. RobertsAbstract:Although several models have been proposed to account for how cytoskeleton polymerization drives protrusion in cell motility, the precise mechanism remains controversial. Here, we show that, in addition to force exerted directly against the membrane by growing filaments, the way elongating filaments pack also contributes to protrusion by generating an expansion of the cytoskeleton gel. Tomography shows that filament packing in the Major Sperm Protein (MSP) -based nematode Sperm-motility machinery resembles that observed with rigid rods. Maximum rod-packing density decreases dramatically as the rods lengthen. Therefore, as filaments elongate, the cytoskeleton gel expands to accommodate their packing less densely. This volume expansion combines with polymerization to drive protrusion. Consistent with this hypothesis, an engineered MSP mutant that generates shorter filaments shows higher filament-packing density and slower movement.
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a ser thr kinase required for membrane associated assembly of the Major Sperm Protein motility apparatus in the amoeboid Sperm of ascaris
Molecular Biology of the Cell, 2007Co-Authors: Shawnna M. Buttery, Murray Stewart, Thomas M. RobertsAbstract:Leading edge protrusion in the amoeboid Sperm of Ascaris suum is driven by the localized assembly of the Major Sperm Protein (MSP) cytoskeleton in the same way that actin assembly powers protrusion in other types of crawling cell. Reconstitution of this process in vitro led to the identification of two accessory Proteins required for MSP polymerization: an integral membrane phosphoProtein, MSP polymerization-organizing Protein (MPOP), and a cytosolic component, MSP fiber Protein 2 (MFP2). Here, we identify and characterize a 34-kDa cytosolic Protein, MSP polymerization-activating kinase (MPAK) that links the activities of MPOP and MFP2. Depletion/add-back assays of Sperm extracts showed that MPAK, which is a member of the casein kinase 1 family of Ser/Thr Protein kinases, is required for motility. MPOP and MPAK comigrated by native gel electrophoresis, coimmunoprecipitated, and colocalized by immunofluorescence, indicating that MPOP binds to and recruits MPAK to the membrane surface. MPAK, in turn, phosphorylated MFP2 on threonine residues, resulting in incorporation of MFP2 into the cytoskeleton. Beads coated with MPAK assembled a surrounding cloud of MSP filaments when incubated in MPAK-depleted Sperm extract, but only when supplemented with detergent-solubilized MPOP. Our results suggest that interactions involving MPOP, MPAK, and MFP2 focus MSP polymerization to the plasma membrane at the leading edge of the cell thereby generating protrusion and minimizing nonproductive filament formation elsewhere.
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A Ser/Thr kinase required for membrane-associated assembly of the Major Sperm Protein motility apparatus in the amoeboid Sperm of Ascaris
Molecular biology of the cell, 2007Co-Authors: Shawnna M. Buttery, Murray Stewart, Thomas M. RobertsAbstract:Leading edge protrusion in the amoeboid Sperm of Ascaris suum is driven by the localized assembly of the Major Sperm Protein (MSP) cytoskeleton in the same way that actin assembly powers protrusion in other types of crawling cell. Reconstitution of this process in vitro led to the identification of two accessory Proteins required for MSP polymerization: an integral membrane phosphoProtein, MSP polymerization-organizing Protein (MPOP), and a cytosolic component, MSP fiber Protein 2 (MFP2). Here, we identify and characterize a 34-kDa cytosolic Protein, MSP polymerization-activating kinase (MPAK) that links the activities of MPOP and MFP2. Depletion/add-back assays of Sperm extracts showed that MPAK, which is a member of the casein kinase 1 family of Ser/Thr Protein kinases, is required for motility. MPOP and MPAK comigrated by native gel electrophoresis, coimmunoprecipitated, and colocalized by immunofluorescence, indicating that MPOP binds to and recruits MPAK to the membrane surface. MPAK, in turn, phosphorylated MFP2 on threonine residues, resulting in incorporation of MFP2 into the cytoskeleton. Beads coated with MPAK assembled a surrounding cloud of MSP filaments when incubated in MPAK-depleted Sperm extract, but only when supplemented with detergent-solubilized MPOP. Our results suggest that interactions involving MPOP, MPAK, and MFP2 focus MSP polymerization to the plasma membrane at the leading edge of the cell thereby generating protrusion and minimizing nonproductive filament formation elsewhere.
Michael A. Miller - One of the best experts on this subject based on the ideXlab platform.
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the secreted msp domain of c elegans vapb homolog vpr 1 patterns the adult striated muscle mitochondrial reticulum via smn 1
Development, 2017Co-Authors: Jessica Schultz, Jack Vibbert, Pauline Cottee, Tim Cole, Hieu D Hoang, Michael A. MillerAbstract:The Major Sperm Protein domain (MSPd) has an extracellular signaling function implicated in amyotrophic lateral sclerosis. Secreted MSPds derived from the C. elegans VAPB homolog VPR-1 promote mitochondrial localization to actin-rich I-bands in body wall muscle. Here we show that the nervous system and germ line are key MSPd secretion tissues. MSPd signals are transduced through the CLR-1 Lar-like tyrosine phosphatase receptor. We show that CLR-1 is expressed throughout the muscle plasma membrane, where it is accessible to MSPd within the pseudocoelomic fluid. MSPd signaling is sufficient to remodel the muscle mitochondrial reticulum during adulthood. An RNAi suppressor screen identified survival of motor neuron 1 (SMN-1) as a downstream effector. SMN-1 acts in muscle, where it colocalizes at myofilaments with ARX-2, a component of the Arp2/3 actin-nucleation complex. Genetic studies suggest that SMN-1 promotes Arp2/3 activity important for localizing mitochondria to I-bands. Our results support the model that VAPB homologs are circulating hormones that pattern the striated muscle mitochondrial reticulum. This function is crucial in adults and requires SMN-1 in muscle, likely independent of its role in pre-mRNA splicing.
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secreted vapb als8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors
Developmental Cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Se Jin Lee, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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Secreted VAPB/ALS8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors.
Developmental cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jin Lee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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an eph receptor Sperm sensing control mechanism for oocyte meiotic maturation in caenorhabditis elegans
Genes & Development, 2003Co-Authors: Michael A. Miller, Paul J Ruest, Mary Kosinski, Steven K Hanks, David GreensteinAbstract:During sexual reproduction in most animals, oocytes arrest in meiotic prophase and resume meiosis (meiotic maturation) in response to Sperm or somatic cell signals. Despite progress in delineating mitogen-activated Protein kinase (MAPK) and CDK/cyclin activation pathways involved in meiotic maturation, it is less clear how these pathways are regulated at the cell surface. The Caenorhabditis elegans Major Sperm Protein (MSP) signals oocytes, which are arrested in meiotic prophase, to resume meiosis and ovulate. We used DNA microarray data and an in situ binding assay to identify the VAB-1 Eph receptor Protein-tyrosine kinase as an MSP receptor. We show that VAB-1 and a somatic gonadal sheath cell-dependent pathway, defined by the CEH-18 POU-class homeoProtein, negatively regulate meiotic maturation and MAPK activation. MSP antagonizes these inhibitory signaling circuits, in part by binding VAB-1 on oocytes and sheath cells. Our results define a Sperm-sensing control mechanism that inhibits oocyte maturation, MAPK activation, and ovulation when Sperm are unavailable for fertilization. MSP-domain Proteins are found in diverse animal taxa, where they may regulate contact-dependent Eph receptor signaling pathways.
Sung Min Han - One of the best experts on this subject based on the ideXlab platform.
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secreted vapb als8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors
Developmental Cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Se Jin Lee, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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Secreted VAPB/ALS8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors.
Developmental cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jin Lee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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The amyotrophic lateral sclerosis 8 Protein VAPB is cleaved, secreted, and acts as a ligand for Eph receptors.
Cell, 2008Co-Authors: Hiroshi Tsuda, Sung Min Han, Youfeng Yang, Claire Haueter, Chao Tong, Yong Qi Lin, Kriti Mohan, Anthony William Zoghbi, Yadollah Harati, Justin Y. KwanAbstract:VAP Proteins (human VAPB/ALS8, Drosophila VAP33, and C. elegans VPR-1) are homologous Proteins with an amino-terminal Major Sperm Protein (MSP) domain and a transmembrane domain. The MSP domain is named for its similarity to the C. elegans MSP Protein, a Sperm-derived hormone that binds to the Eph receptor and induces oocyte maturation. A point mutation (P56S) in the MSP domain of human VAPB is associated with Amyotrophic lateral sclerosis (ALS), but the mechanisms underlying the pathogenesis are poorly understood. Here we show that the MSP domains of VAP Proteins are cleaved and secreted ligands for Eph receptors. The P58S mutation in VAP33 leads to a failure to secrete the MSP domain as well as ubiquitination, accumulation of inclusions in the endoplasmic reticulum, and an unfolded Protein response. We propose that VAP MSP domains are secreted and act as diffusible hormones for Eph receptors. This work provides insight into mechanisms that may impact the pathogenesis of ALS.
Pauline Cottee - One of the best experts on this subject based on the ideXlab platform.
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the secreted msp domain of c elegans vapb homolog vpr 1 patterns the adult striated muscle mitochondrial reticulum via smn 1
Development, 2017Co-Authors: Jessica Schultz, Jack Vibbert, Pauline Cottee, Tim Cole, Hieu D Hoang, Michael A. MillerAbstract:The Major Sperm Protein domain (MSPd) has an extracellular signaling function implicated in amyotrophic lateral sclerosis. Secreted MSPds derived from the C. elegans VAPB homolog VPR-1 promote mitochondrial localization to actin-rich I-bands in body wall muscle. Here we show that the nervous system and germ line are key MSPd secretion tissues. MSPd signals are transduced through the CLR-1 Lar-like tyrosine phosphatase receptor. We show that CLR-1 is expressed throughout the muscle plasma membrane, where it is accessible to MSPd within the pseudocoelomic fluid. MSPd signaling is sufficient to remodel the muscle mitochondrial reticulum during adulthood. An RNAi suppressor screen identified survival of motor neuron 1 (SMN-1) as a downstream effector. SMN-1 acts in muscle, where it colocalizes at myofilaments with ARX-2, a component of the Arp2/3 actin-nucleation complex. Genetic studies suggest that SMN-1 promotes Arp2/3 activity important for localizing mitochondria to I-bands. Our results support the model that VAPB homologs are circulating hormones that pattern the striated muscle mitochondrial reticulum. This function is crucial in adults and requires SMN-1 in muscle, likely independent of its role in pre-mRNA splicing.
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secreted vapb als8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors
Developmental Cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Se Jin Lee, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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Secreted VAPB/ALS8 Major Sperm Protein domains modulate mitochondrial localization and morphology via growth cone guidance receptors.
Developmental cell, 2012Co-Authors: Sung Min Han, Hiroshi Tsuda, Youfeng Yang, Jack Vibbert, Pauline Cottee, Jin Lee, Jessica Winek, Claire Haueter, Hugo J. Bellen, Michael A. MillerAbstract:Summary The VAPB/ALS8 Major Sperm Protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila , the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like Protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function. Video Abstract
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characterization of Major Sperm Protein genes and their expression in oesophagostomum dentatum nematoda strongylida
Parasitology, 2004Co-Authors: Pauline Cottee, A J Nisbet, P R Boag, M Larsen, R B GasserAbstract:Major Sperm Protein ( msp ) genes were isolated from complementary (cDNA) and genomic DNA libraries prepared from the parasitic nematode, Oesophagostomum dentatum , characterized at the nucleotide and amino acid (aa) levels, and their expression was investigated. Three different msp cDNA and 2 genomic sequences were determined The nucleotide sequences reported in this article have been deposited in the EMBL, GenBank and DDJB databases under the Accession numbers AJ627869–AJ627873. , each with an open reading frame (ORF) of 381 nucleotides. Nucleotide variation was detected at 30 positions in the ORF among all 5 sequences. Conceptual translation of the full-length msp sequences inferred 4 different MSPs each of 126 aa. These predicted MSPs differed at aa positions 15 (serine threonine), 101 (alanine glycine), 103 (glutamine leucine) and 126 (proline leucine). Southern blot analysis of O. dentatum genomic DNA, digested separately with various restriction endonucleases, displayed multiple ( n =7–13) bands for each enzyme, providing support for a multigene family. Also, at the genomic level, sequence tracts consistent with a ‘substitute’ TATA box sequence motif were identified within a region (−1 to −123 nt) preceding the 2 msp genes. In contrast to other species of nematode investigated to date, no GATA transcription factor binding motif was detected immediately upstream of the msp coding region. Real-time PCR analysis demonstrated that msp mRNA was expressed exclusively in the males of both fourth-stage larvae (L4s) and adults of O. dentatum (raised in pigs after intragastric inoculation). The magnitude of expression in male O. dentatum raised in pigs in the presence of female worms was the same as in males in the absence of females. Comparative analyses showed aa sequence conservation among MSPs from various nematodes, suggesting similar functional roles for these Proteins.
