Differential Requirement for the Nonhelical Tailpiece and the C Terminus of the Myosin Rod inCaenorhabditis elegansMuscle

Abstract

Myosin heavy chain (MHC) is a large, multidomain protein important for both cellular structure and contraction. To examine the functional role of two C-terminal domains, the end of the coiled-coil rod and the nonhelical tailpiece, we have generated constructs in which residues within these domains are removed or mutated, and examined their behavior in Caenorhabditis elegans striated muscle. Genetic tests demonstrate that MHC lacking only tailpiece residues is competent to support the timely onset of embryonic contractions, and therefore viability, in animals lacking full-length MHC. Antibody staining experiments show that this truncated molecule localizes as wild type in early stages of development, but may be defective in processes important for thick filament organization later in embryogenesis. Ultrastructural analysis reveals thick filaments of normal morphology in disorganized arrangement, as well as occasional abnormal assemblages. In contrast, molecules in which the four terminal residues of the coiled coil are absent or mutated fail to rescue animals lacking endogenous MHC. Loss of these four residues is associated with delayed protein localization and delayed contractile function during early embryogenesis. Our results suggest that these two MHC domains, the rod and the tailpiece, are required for distinct steps during muscle development.

Caenorhabditis elegans unc-82 Encodes a Serine/Threonine Kinase Important for Myosin Filament Organization in Muscle During Growth

“…Abnormal thick-filament structures found in unc-82 mutants contain both myosin and paramyosin (Epstein et al 1987). The possibility that myosin is a target of UNC-82 is supported by the observation that the myosin phenotype observed in unc-82 mutant embryos is similar to that caused by removal of the phosphorylation motifs contained in the myosin nonhelical tailpiece: early patterning of myosin is normal, but aberrant patchy distribution appears as elongation proceeds (Hoppe et al 2003). While the mechanisms guiding thick filament elongation and placement during growth are not well understood in striated muscle, many prior studies have examined the regulation of assembly and disassembly of nonmuscle and smooth muscle myosins by phosphorylation (Castellani and Cohen 1987;Castellani et al 1988;reviews: Moussavi et al 1993;Brzeska and Korn 1996;Redowicz 2001;Bosgraafa and van Haastert 2006).…”

Myosin isoform switching during assembly of the Drosophila flight muscle thick filament lattice

“…In non-muscle myosin the tailpiece can promote filament assembly (Hodge et al, 1992;Ronen and Ravid, 2009), while its removal affects the stability of in vitro rod assemblies either positively or negatively, depending on the isoform (Ronen et al, 2010). Conversely, some studies claim that the tailpiece is not directly important for thick filament assembly itself (Ikebe et al, 2001, Hoppe et al, 2003, but might be required for stable positioning of the filaments in the sarcomere (Hoppe et al, 2003).…”

Oral Fibroblast Expression of wound-inducible transcript 3.0 (wit3.0) Accelerates the Collagen Gel Contraction in Vitro

“…Myosin heavy chain II molecules are dimerized through the coiled-coil ␣-helix and provide the phosphorylation site. Thus, the coiled-coil domain is thought to regulate the ability of the myosin to produce force (25)(26)(27). The peptide sequence of wit3.0␤ suggests a potential ␣-helix structure (Fig.…”