αB-Crystallin Phosphorylation: Advances and Problems

The review is dedicated to phosphorylation of alpha B-crystallin (HspB5), one of ubiquitously expressed small heat shock proteins. We describe the structure and properties of alpha B-crystallin and protein kinases involved in its phosphorylation in different cells and tissues, advantages and drawbacks of pseudophosphorylation mutants in elucidation of the mechanism of alpha B-crystallin functioning, effects of phosphorylation on the quaternary structure and intracellular location of alpha B-crystallin, interactions of alpha B-crystallin with different elements of the cytoskeleton, and effect of phosphorylation on the chap-erone-like activity of alpha B-crystallin. We also discuss the validity of experimental data obtained by overexpression of pseudophosphorylation mutants for understanding the effect of phosphorylation on physiologically important properties of alpha B-crystallin, as well as the question why multiple attempts to phosphorylate alpha B-crystallin in vitro have been unsuccessful so far.