title: The C terminus of collagen SQT-3 has complex and essential functions in nematode collagen assembly.
abstract: The nematode exoskeleton is a multilayered structure secreted by the underlying hypodermal cells and mainly composed of small collagens, which are encoded by a large gene family. In previous work, we reported analysis of the C. elegans dpy-31 locus, encoding a hypodermally expressed zinc-metalloprotease of the BMP-1/TOLLOID family essential for viability and cuticle deposition. We have generated a large set of extragenic suppressors of dpy-31 lethality, most of which we show here to be allelic to the cuticle collagen genes sqt-3 and dpy-17. We analyzed the interaction among dpy-31, sqt-3, and dpy-17 using a SQT-3-specific antiserum, which was employed in immunofluorescence experiments. Our results support a role for DPY-31 in SQT-3 extracellular processing and suggest that the SQT-3 C-terminal nontrimeric region serves multiple roles during SQT-3 assembly. Different missense mutations of this region have diverse phenotypic consequences, including cold-sensitive lethality. Furthermore, the biochemical and genetic data indicate that the extracellular assemblies of DPY-17 and SQT-3 are interdependent, most likely because the collagens are incorporated into the same cuticular substructure. We find that absence of DPY-17 causes extensive intracellular retention of SQT-3, indicating that formation of the SQT-3-DPY-17 polymer could begin in the intracellular environment before secretion.
authors.affiliation: Genetics Unit, Department of Biochemistry, University of Oxford, United Kingdom.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Novelli
authors.forename: Antony P
authors.initials: AP
authors.lastname: Page
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hodgkin
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003094:Collagen / Q000737:chemistry*; D015801:Helminth Proteins / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D024041:Non-Fibrillar Collagens; D011108:Polymers / Q000737:chemistry; D017434:Protein Structure, Tertiary; D019076:Transgenes
chemical_list: D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D024041:Non-Fibrillar Collagens; D011108:Polymers; C511741:SQT-3 protein, C elegans; C116307:dpy-17 protein, C elegans; D003094:Collagen; C511740:DPY-31 protein, C elegans; D008666:Metalloendopeptidases