title: Loss of secretory pathway FK506-binding proteins results in cold-sensitive lethality and associate extracellular matrix defects in the nematode Caenorhabditis elegans.
abstract: The FK506-binding proteins (FKBs) represent ubiquitous enzymes that catalyze the rate-limiting peptidyl prolyl cis-trans isomerization step in protein folding. The nematode Caenorhabditis elegans has eight FKBs, three of which (FKB-3, -4, and -5) have dual peptidyl prolyl cis-trans isomerase (PPIase) domains, signal peptides and ER retention signals. PPIase activity has been detected for recombinant FKB-3. Both FKB-3 and -5 are expressed in the exoskeleton-synthesizing hypodermis with transcript peaks that correspond to the molting and collagen synthesis cycles. FKB-4 is expressed at a low level throughout development. No phenotypes were observed in deletion mutants in each of the secretory pathway FKBs. Combined triple and fkb-4, -5 double deletion mutants were however found to arrest at 12 degrees C, but developed normally at 15-25 degrees C. This cold-sensitive larval lethal effect was not maternally derived, occurred during embryogenesis, and could be rescued following the transgenic introduction of a wild type copy of either fkb-4 or fkb-5. The temperature-sensitive defects also affected molting, cuticle collagen expression, hypodermal seam cell morphology, and the structural integrity of the cuticular extracellular matrix. This study establishes that the secretory pathway FK506-binding PPIase enzymes are essential for normal nematode development, collagen biogenesis, and the formation of an intact exoskeleton under adverse physiological conditions.
authors.affiliation: Institute of Comparative Medicine, Faculty of Veterinary Medicine, The University of Glasgow, Bearsden Road, Glasgow G61 1QH, Scotland, United Kingdom.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Winter
authors.forename: Sylvain C P
authors.initials: SC
authors.lastname: Eschenlauer
authors.forename: Gillian
authors.initials: G
authors.lastname: McCormack
authors.forename: Antony P
authors.initials: AP
authors.lastname: Page
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D003094:Collagen / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism* / Q000473:pathology; D017353:Gene Deletion; D018978:Molting / Q000235:genetics; D019696:Peptidylprolyl Isomerase / Q000172:deficiency*; D022021:Tacrolimus Binding Proteins / Q000172:deficiency*
chemical_list: D029742:Caenorhabditis elegans Proteins; D003094:Collagen; D022021:Tacrolimus Binding Proteins; C403485:tacrolimus binding protein 4; D019696:Peptidylprolyl Isomerase