Phosphorylation of ribosomal protein S19 at Ser59 by CaM Kinase Iα |
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Authors: | Noriko Maeda Seikichi Toku Yasuhito Naito† Hiroshi Nishiura‡ Tatsuo Tanaka§ Hideyuki Yamamoto |
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Institution: | Department of Biochemistry, School of Medicine, University of the Ryukyus, Okinawa, Japan; Department of Pharmacology, School of Pharmaceutical Science, Kitasato University, Tokyo, Japan; Department of Molecular Pathology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan; Okinawa College of Rehabilitation and Welfare, Okinawa, Japan |
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Abstract: | In order to examine the possible involvements of Ca2+/calmodulin-dependent protein kinases (CaM kinases) in the regulation of ribosomal functions, we tested the phosphorylation of rat ribosomal protein S19 (RPS19) by various CaM kinases in vitro . We found that CaM kinase Iα, but not CaM kinase Iβ1, Iβ2, II, or IV, robustly phosphorylated RPS19. From the consensus phosphorylation site sequence, Ser59, Ser90, and Thr124 were likely to be phosphorylated; therefore, we mutated each amino acid to alanine and found that the mutation of Ser59 to alanine strongly attenuated phosphorylation by CaM kinase Iα, suggesting that Ser59 was a major phosphorylation site. Furthermore, we produced a specific antibody against RPS19 phosphorylated at Ser59, and found that Ser59 was phosphorylated both in GT1-7 cells and rat brain. Phosphorylation of RPS19 in GT1-7 cells was inhibited by KN93, an inhibitor of CaM kinases. Immunoblot analysis after subcellular fractionation of rat brain demonstrated that phosphorylated RPS19 was present in 80S ribosomes. Phosphorylation of RPS19 by CaM kinase Iα augmented the interaction of RPS19 with the previously identified S19 binding protein. These results suggest that CaM kinase Iα regulates the functions of RPS19 through phosphorylation of Ser59. |
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Keywords: | calmodulin Ca2+/calmodulin-dependent protein kinase I Diamond-Blackfan anemia phosphorylation ribosomal protein S19 |
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