αB-Crystallin phosphorylated at Ser-59 is localized in centrosomes and midbodies during mitosis

Abstract

We have reported that the three serine residues in alphaB-crystallin are phosphorylated under various stress conditions. We prepared affinity-purified antibodies recognizing each of the phosphorylated serine residues (Ser-19, Ser-45, and Ser-59, respectively) in alphaB-crystallin with peptides (p19S, p45S, or p59S) that contained the corresponding phosphorylated serine residue. Immunocytochemically anti-p45S antibodies stained the cytoplasm of mitotic cells (J. Biol. Chem. 273, 28,346-28,354). We have now found that the anti-p59S antibodies recognize centrosomes and midbodies of dividing cells. alphaB-Crystallin was the only protein recognized by the anti-p59S antibodies in Western blot analyses of isolated centrosome fractions. alphaB-Crystallin phosphorylated at Ser-59 was localized at the microtubule organizing centers by means of double staining with anti-beta-tubulin antibody in aster formation analysis and was co-localized with gamma-tubulin in centrosomes. Gamma-Tubulin was co-immunoprecipitated with alphaB-crystallin in U373 glioma cell extracts. On the other hand, the location of the phosphorylated alphaB-crystallin deviated from that of alpha-tubulin or gamma-tubulin in the midbody region. Taken together with the evidences that several chaperones are distributed to centrosomes, these results suggest that alphaB-crystallin as a chaperone might be also involved in the quality control of proteins.