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

HSP25, a previously uncharacterized member of the alpha-crystallin family o f small heat shock proteins in Caenorhabditis elegans, has been examined us ing biochemical and immunological techniques. HSP25 is the second largest o f 16 identifiable small heat shock proteins in the nematode and is expresse d at all developmental stages under normal growth conditions. Recombinant H SP25 produced in Escherichia coil exists predominantly as small oligomers ( dimers to tetramers) and possesses chaperone activity against citrate synth ase 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 be tween cells of the spermathecal wall. Affinity chromatography of nematode e xtracts on a column of immobilized HSP25 resulted in specific binding of vi nculin and alpha-actinin but not actin, as revealed by Western blotting. Th ese results suggest a role for HSP25 in the organization or maintenance of the myofilament lattice and adherens junctions in C. elegans.