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

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.

Segregated localization of two calponin‐related proteins within sarcomeric thin filaments in Caenorhabditis elegans striated muscle

“…This segregation is most likely due to their competitive binding to actin filaments (Drabikowski et al, 1968; Drabikowski & Nowak, 1968). Similarly, in invertebrate muscles, kettin, a connectin/titin‐related protein, is associated with sarcomeric actin filaments near the actin barbed ends due to competition with tropomyosin (Lakey et al, 1993; K. Ono et al, 2006, 2020; van Straaten et al, 1999). Likewise, there may be an unknown factor(s) that regulates segregation of UNC‐87 and CLIK‐1.…”

“…Immunofluorescent staining of UNC‐87, UNC‐94, and actin (Figures 6a, 7c, and 8) was performed with the method of Nonet et al (1997). Other immunofluorescent staining experiments (Figure 7a,b) were performed with the freeze‐crack method as described previously (K. Ono et al, 2020). Briefly, adult worms were anesthetized by 0.1% tricaine and 0.01% levamisole and cut in half using a pair of 28‐gauge needles on polylysine‐coated glass slides.…”

The intestinal milieu influences the immunoproteome of male and femaleHeligmosomoides polygyrus bakeriL4 stage

“…Another immunogenic protein was kettin, which was recognized in male and female L4 from control mice but not from mice with colitis. Kettin is essential for sarcomeric assembly of actin filaments in muscle cells in Caenorhabditis elegans (Ono et al ., 2020).…”

“…colitis. Kettin is essential for sarcomeric assembly of actin filaments in muscle cells in Caenorhabditis elegans (Ono et al, 2020). Immunogenic succinate dehydrogenase, flavoprotein subunit was observed in male L4 from control mice and female L4 from mice with colitis.…”

The α-arrestin SUP-13/ARRD-15 promotes isoform turnover of actin-interacting protein 1 in Caenorhabditis elegans striated muscle

“…We sequenced RW2337 sup-13(st210) III;unc-78(e1217) X and CB1217 unc-78(e1217) X as described previously ( 71 ). Genomic DNA was submitted to the British Columbia Cancer Agency Canada’s Michael Smith Genome Sciences Centre for whole-genome sequencing using the Illumina PET HiSeq technology to produce 150 bp long paired end reads.…”