RRC ID 28966
Author Chen P, Ostrow BD, Tafuri SR, Chisholm RL.
Title Targeted disruption of the Dictyostelium RMLC gene produces cells defective in cytokinesis and development.
Journal J Cell Biol
Abstract Conventional myosin has two different light chains bound to the neck region of the molecule. It has been suggested that the light chains contribute to myosin function by providing structural support to the neck region, therefore amplifying the conformational changes in the head following ATP hydrolysis (Rayment et al., 1993). The regulatory light chain is also believed to be important in regulating the actin-activated ATPase and myosin motor function as assayed by an in vitro motility assay (Griffith et al., 1987). Despite extensive in vitro biochemical study, little is known regarding RMLC function and its regulatory role in vivo. To better understand the importance and contribution of RMLC in vivo, we engineered Dictyostelium cell lines with a disrupted RMLC gene. Homologous recombination between the introduced gene disruption vector and the chromosomal RMLC locus (mlcR) resulted in disruption of the RMLC-coding region, leading to cells devoid of both the RMLC transcript and the 18-kD RMLC polypeptide. RMLC-deficient cells failed to divide in suspension, becoming large and multinucleate, and could not complete development following starvation. These results, similar to those from myosin heavy chain mutants (DeLozanne et al., 1987; Manstein et al., 1989), suggest the RMLC subunit is required for normal cytokinesis and cell motility. In contrast to the myosin heavy chain mutants, however, the mlcR cells are able to cap cell surface receptors following concanavilin A treatment. By immunofluorescence microscopy, RMLC null cells exhibited myosin localization patterns different from that of wild-type cells. The myosin localization in RMLC null cells also varied depending upon whether the cells were cultured in suspension or on a solid substrate. In vitro, purified RMLC- myosin assembled to form thick filaments comparable to wild-type myosin, but the filaments then exhibit abnormal disassembly properties. These results indicate that in vivo RMLC is necessary for myosin function.
Volume 127(6 Pt 2)
Pages 1933-44
Published 1994-12-1
DOI 10.1083/jcb.127.6.1933
PMID 7806571
PMC PMC2120281
MeSH Actins / isolation & purification Animals Blotting, Western Calcium-Transporting ATPases / analysis Cell Aggregation Cell Division Cytoskeleton / enzymology DNA, Protozoan / genetics DNA, Recombinant Dictyostelium / genetics Dictyostelium / growth & development* Fluorescent Antibody Technique Genes, Protozoan / genetics* Microscopy, Fluorescence Mutagenesis Myosins / genetics* Myosins / metabolism Myosins / ultrastructure Phenotype Transformation, Genetic
IF 8.811
Times Cited 74
Cellular slime molds S00033