α-Crystallin Stabilizes Actin Filaments and Prevents Cytochalasin-Induced Depolymerization in a Phosphorylation-Dependent Manner
Article first published online: 23 JUL 2004
European Journal of Biochemistry
Volume 242, Issue 1, pages 56–66, November 1996
How to Cite
Wang, K. and Spector, A. (1996), α-Crystallin Stabilizes Actin Filaments and Prevents Cytochalasin-Induced Depolymerization in a Phosphorylation-Dependent Manner. European Journal of Biochemistry, 242: 56–66. doi: 10.1111/j.1432-1033.1996.0056r.x
- Issue published online: 23 JUL 2004
- Article first published online: 23 JUL 2004
- (Received 3 July/16 September 1996) – EJB 96 0982/3
- heat-shock protein;
α-crystallin, a major lens protein of approximately 800 kDa with subunits of about 20 kDa has previously been shown to act as a chaperone protecting other proteins from stress-induced damage and to share sequence similarity with small heat-shock proteins, sHsp. It is now demonstrated that this chaperone effect extends to protection of the intracellular matrix component actin. It was found that the powerful depolymerization effect of cytochalasin D could be almost completely blocked by α-crystallin, αA-crystallin or αB-crystallin. However, phosphorylation of α-crystallin markedly decreased its protective effect. It is suggested that phosphorylation of α-crystallin may contribute to changes in actin structure observed during cellular remodeling that occurs with the terminal differentiation of a lens epithelial cell to a fiber cell and contributes to cellular remodeling in other cell types that contain α-crystallin species. This communication presents biochemical evidence clearly demonstrating that α-crystallin is involved in actin polymerization-depolymerization dynamics.
It is also shown that α-crystallin prevented heat-induced aggregation of actin filaments. α-crystallin was found to stabilize actin polymers decreasing dilution-induced depolymerization rates up to twofold while slightly decreasing the critical concentration from 0.23 μM to 0.18 μM. Similar results were found with either α-crystallin or its purified subunits αA-crystallin and αB-crystallin. In contrast to the experiments with cytochalasin D, phosphorylation had no effect. There does not appear to be an interaction between α-crystallin and actin monomers since the effect of α-crystallin in enhancing actin polymerization does not become apparent until some polymerization has occurred. Examination of the stoichiometry of the α-crystallin effect indicates that 2-3 α-crystallin monomers/actin monomer give maximum actin polymer stabilization.