alpha B-crystallin in the rat lens is phosphorylated at an early post-natal age

We determined the developmental changes in the phosphorylation state of alp ha B-crystallin in lenses from rats at various post-natal ages by isoelectr ic focusing gel electrophoresis or sodium dodecyl sulfate-polyacrylamide ge l electrophoresis and a subsequent Western blot analysis of extracts of len ses using antibodies that recognized the carboxy-terminal sequence or each of the three phosphorylated serine residues (Ser-19, Ser-45 and Ser-59) in alpha B-crystallin. Phosphorylated forms of alpha B-crystallin were barely detected at birth but they became detectable at 3 weeks of age and reached plateau levels at 8 weeks of age. The phosphorylation of alpha B-crystallin at Ser-45 was observed preferentially. The active form of p44/42 MAP kinas e, which is responsible for the phosphorylation of Ser-45 in alpha B-crysta llin, also increased in a development-dependent manner. Thus we found that the developmental increase of the phosphorylation at Ser-45 of alpha B-crys tallin in the rat lens was due to the developmental activation of p44/42 MA P kinase, (C) 1999 Federation of European Biochemical Societies.