We have previously reported that, in neuroblastoma LAN-5 cells, calpastatin is in an aggregated state, close to the cell nucleus [De Tullio, Passalacqua, Averna, Salamino, Melloni and Pontremoli (1999) Biochem. J. 343, 467–472]. In the present paper, we demonstrate that aggregated calpastatin is predominantly in a phosphorylated state. An increase in intracellular free [Ca2+] induces both dephosphorylation of calpastatin, through the action of a phosphoprotein phosphatase, and its redistribution as a soluble inhibitor species. cAMP, but not PMA-induced phosphorylation, reverses calpastatin distribution favouring its aggregation. This intracellular reversible mechanism, regulating the level of cytosolic calpastatin, could be considered a strategy through which calpain can escape calpastatin inhibition, especially during earlier steps of its activation process.
Changes in intracellular calpastatin localization are mediated by reversible phosphorylation
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Monica AVERNA, Roberta DE TULLIO, Mario PASSALACQUA, Franca SALAMINO, Sandro PONTREMOLI, Edon MELLONI; Changes in intracellular calpastatin localization are mediated by reversible phosphorylation. Biochem J 15 February 2001; 354 (1): 25–30. doi: https://doi.org/10.1042/bj3540025
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