Phosphorylation and subcellular distribution of calpastatin in human hematopoietic system cells

• Published in: The Journal of biological chemistry 1991-02, Vol.266 (6), p.3968-3972
• Main Authors: Adachi, Y, Ishida-Takahashi, A, Takahashi, C, Takano, E, Murachi, T, Hatanaka, M
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Bone Marrow - drug effects; Bone Marrow - metabolism; Bone Marrow Cells; Calcium-Binding Proteins - metabolism; Cell Fractionation; Cells, Cultured; Electrophoresis, Polyacrylamide Gel; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Humans; Hydrolases; Molecular Sequence Data; Peptide Mapping; Precipitin Tests; Tetradecanoylphorbol Acetate - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)67888-9

Calpastatin is an endogenous inhibitor protein acting specifically on calpain (EC 3.4.22.17; Ca2(+)-dependent cysteine proteinase). The phosphorylation of calpastatin was investigated in human hematopoietic system cell lines. Microheterogeneity of calpastatin was observed, in which 118- and 116-kDa forms were named calpastatin a and b, respectively. The phosphorylation of both calpastatins was identified in all cell lines examined and occurred mainly at serine residues with trace amounts of phosphothreonine in vivo. The incubation of cells with 12-O-tetradecanoylphorbol-13-acetate increased the incorporation of 32P-orthophosphate into calpastatin a. Two-dimensional maps of 32P-labeled phosphopeptide from both calpastatins were identical except for additional minor spots for calpastatin a. [35S]methionine-labeled calpastatins a and b were localized mainly in the cytosol, and only 6% of cellular calpastatins were detected in the membrane fraction. By contrast, more than 30% of the 32P-labeled calpastatins a and b were distributed in the membrane fraction. Thus, the phosphorylation of calpastatin may be involved in regulating the calpain-calpastatin protein kinase system by its subcellular distribution.