title: FER-1 regulates Ca2+ -mediated membrane fusion during C. elegans spermatogenesis.
abstract: FER-1 is required for fusion of specialized vesicles, called membranous organelles, with the sperm plasma membrane during Caenorhabditis elegans spermiogenesis. To investigate its role in membranous organelle fusion, we examined ten fer-1 mutations and found that they all cause the same defect in membrane fusion. FER-1 and the ferlin protein family are membrane proteins with four to seven C2 domains. These domains commonly mediate Ca2+ -dependent lipid-processing events. Most of the fer-1 mutations fall within these C2 domains, showing that they have distinct, non-redundant functions. We found that membranous organelle fusion requires intracellular Ca2+ and that C2 domain mutations alter Ca2+ sensitivity. This suggests that the C2 domains are involved in Ca2+ sensing and further supports their independent function. Using two immunological approaches we found three FER-1 isoforms, two of which might arise from FER-1 by proteolysis. By both light and electron microscopy, these FER-1 proteins were found to be localized to membranous organelle membranes. Dysferlin, a human homologue of FER-1 involved in muscular dystrophy, is required for vesicle fusion during Ca2+ -induced muscle membrane repair. Our results suggest that the ferlin family members share a conserved mechanism to regulate cell-type-specific membrane fusion.
authors.affiliation: Department of Molecular and Cellular Biology, The University of Arizona, 1007 E. Lowell Street, Life Sciences South 452, Tucson, AZ, 85721, USA.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Washington
authors.forename: Samuel
authors.initials: S
authors.lastname: Ward
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D008297:Male; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D008854:Microscopy, Electron; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D012680:Sensitivity and Specificity; D013091:Spermatogenesis / Q000235:genetics / Q000502:physiology*; D013094:Spermatozoa / Q000737:chemistry
chemical_list: D029742:Caenorhabditis elegans Proteins; C106933:FER-1 protein, C elegans; D008565:Membrane Proteins; D020033:Protein Isoforms; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium