The effect of lysophosphatidic acid on the composition of cytoplasmic protein complexes that contain myosin-9 and tropomyosin

Abstract

The present article reports immunofluorescence-based analysis of the distribution of the actin-binding protein myosin-9 in the cytoplasm of human embryonic lung fibroblasts. Electrophoresis and Western blotting were used to demonstrate that myosin-9, actin, and high molecular weight tropomyosin isoforms are incorporated into cytoplasmic protein complexes not bound to cytoskeletal structures. Cross-immunoprecipitation was used to show that these complexes were rapidly disassembled when the cells were exposed to lysophosphatidic acid (LPA). Moreover, LPA induced proteolytic degradation of myosin-9 associated with the structures of the actin cytoskeleton. The results obtained point at the participation of multimolecular cytoplasmic protein complexes that contain myosin-9 and tropomyosin in the regulation of the cellular response to stimulation with LPA.