Kettin, the large actin-binding protein with multiple immunoglobulin domains, is essential for sarcomeric actin assembly and larval development in Caenorhabditis elegans

• Type of Material: Article
• Authors: Shoichiro Ono, Emory University; Zhaozhao Qin, Simon Fraser University; Robert C. Johnsen, Simon Fraser University; David L. Baillie, Simon Fraser University
• Language: English
• Date: 2019-08-24
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2019 Federation of European Biochemical Societies.
• Final Published Version (URL): http://dx.doi.org/10.1111/febs.15039
• Title of Journal or Parent Work: FEBS Journal
• Volume: 287
• Issue: 4
• Start Page: 659
• End Page: 670
• Grant/Funding Information: This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada to D. L. B. and the National Institutes of Health (AR48615) to S. O.
• Keywords: D-TITIN; Z-disc; Caenorhabditis elegans; actin; C-elegans; immunoglobulin domain; Life Sciences & Biomedicine; Contractile apparatuses; Essential genes; genetics; Science & Technology; sarcomere; Striated muscle; Biochemistry & Molecular Biology; Modular disposition; striated muscle; Genomic identification; Dense body; Adhesion-like structures
• Research Categories: Biology, Genetics; Biology, Cell; Biology, Molecular; Health Sciences, Oncology

Abstract

Among many essential genes in the nematode Caenorhabditis elegans, let-330 is located on the left arm of chromosome V and was identified as the largest target of a mutagen in this region. However, let-330 gene has not been characterized at the molecular level. Here, we report that two sequenced let-330 alleles are nonsense mutations of ketn-1, a previously characterized gene encoding kettin. Kettin is a large actin-binding protein of 472 kDa with 31 immunoglobulin domains and is expressed in muscle cells in C. elegans. let-330/ketn-1 mutants are homozygous lethal at the first larval stage with mild defects in body elongation. These mutants have severe defects in sarcomeric actin and myosin assembly in striated muscle. However, α-actinin and vinculin, which are components of the dense bodies anchoring actin to the membranes, were not significantly disorganized by let-330/ketn-1 mutation. Kettin localizes to embryonic myofibrils before α-actinin is expressed, and α-actinin deficiency does not affect kettin localization in larval muscle. Depletion of vinculin minimally affects kettin localization but significantly reduces colocalization of actin with kettin in embryonic muscle cells. These results indicate that kettin is an essential protein for sarcomeric assembly of actin filaments in muscle cells.