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ABSTRACT: Background. Senescence marker protein-30 (SMP30), a calcium binding protein, is preferentially expressed in the renal proximal tubules
and hepatocytes and is presumed to play a role in Ca2+ homeostasis.
Methods. To explore its physiological functions in the tubular cells, we investigated the effect of SMP30 on Ca2+ efflux via the ATP-dependent plasma membrane calcium pump. LLC-PK1 cells were stably transfected with a cDNA encoding SMP30,
and the established transfectants were subjected to ATP responses.
Results. Overexpression of SMP30 significantly increased Ca2+ efflux under both basal and ATP-stimulated conditions. Inhibition of calmodulin by trifluoperazine abrogated the enhanced
Ca2+ efflux, suggesting that SMP30 activated the calmodulin-dependent Ca2+ pump. It is known that Ca2+ superfluous influx induces cellular injury. Compared with mock-transfected cells, LLC-PK1 cells expressing SMP30 showed resistance
to cellular death triggered by Ca2+ superfluous influx.
Conclusion. These results suggest the possibility that, in renal tubular cells, endogenous SMP30 participates in Ca2+ efflux via activating the calmodulin-dependent Ca2+ pump and thereby confers resistance of the cells against injury caused by high intracellular Ca2+ concentrations.
Clinical and Experimental Nephrology 11/1999; 3(4):261-267. · 1.37 Impact Factor
