The effect of stress on the pattern of phosphorylation of alphaA and alphaB crystallin in the rat lens.

Previously, we have shown that phosphorylation of alpha crystallin (alpha) in rat lenses can be stimulated by oxidative stress. To better understand the biological functions of the stress-induced phosphorylation of the A and B chains of alpha (alphaA and alphaB), the normal and stress-induced phosphorylation pattern of these polypeptides in the rat lens has been investigated. With either alphaA or alphaB, there is only one phosphorylation site that is significantly affected, with widely different stresses, H(2)O(2)or elevation in free Ca(++)levels. However, the phosphorylation sites are markedly different for the two polypeptides, for alphaA being on Thr-4 in the N terminal region and with alphaB on Ser-59 in the central region of the polypeptide. The difference in the sequence in the two phosphorylation regions suggests that different phosphorylation systems are probably involved. This implies that the cellular function of the phosphorylation of alphaA and alphaB may be quite different. Copyright 2000 Academic Press.