HSP25, a small heat shock protein associated with dense bodies and M-lines of body wall muscle in Caenorhabditis elegans

HSP25, a previously uncharacterized member of the alpha-crystallin family of small heat shock proteins in Caenorhabditis elegans, has been examined using biochemical and immunological techniques. HSP25 is the second largest of 16 identifiable small heat shock proteins in the nematode and is expressed at all developmental stages under normal growth conditions. Recombinant HSP25 produced in Escherichia coli exists predominantly as small oligomers (dimers to tetramers) and possesses chaperone activity against citrate synthase in vitro. In C. elegans, HSP25 is localized to dense bodies and M-lines in body wall muscle, to the lining of the pharynx, and to the junctions between cells of the spermathecal wall. Affinity chromatography of nematode extracts on a column of immobilized HSP25 resulted in specific binding of vinculin and alpha-actinin but not actin, as revealed by Western blotting. These results suggest a role for HSP25 in the organization or maintenance of the myofilament lattice and adherens junctions in C. elegans.