Journal Article

Early-phase occurrence of K^sup +^ and Cl^sup -^ efflux in addition to Ca^sup 2+^ mobilization is a prerequisite to apoptosis in HeLa cells

Dezaki, Katsuya, Maeno, Emi, Sato, Kaori, Okada, Yasunobu, Akita, Tenpei

2012

Overview

Sustained rise in cytosolic Ca^sup 2+^ and cell shrinkage mainly caused by K^sup +^ and Cl^sup -^ efflux are known to be prerequisites to apoptotic cell death. Here, we investigated how the efflux of K^sup +^ and Cl^sup -^ as well as the rise in cytosolic Ca^sup 2+^ occur prior to caspase activation and are coupled to each other in apoptotic human epithelial HeLa cells. Caspase-3 activation and DNA laddering induced by staurosporine were abolished by blockers of K^sup +^ and Cl^sup -^ channels or cytosolic Ca^sup 2+^ chelation. Staurosporine induced decreases in the intracellular free K^sup +^ and Cl^sup -^ concentrations ([K^sup +^]^sub i^ and [Cl^sup -^]^sub i^) in an early stage prior to caspase-3 activation. Staurosporine also induced a long-lasting rise in the cytosolic free Ca^sup 2+^ concentration. The early-phase decreases in [K^sup +^]^sub i^ and [Cl^sup -^]^sub i^ were completely prevented by a blocker of K^sup +^ or Cl^sup -^ channel, but were not affected by cytosolic Ca^sup 2+^ chelation. By contrast, the Ca^sup 2+^ response was abolished by a blocker of K^sup +^ or Cl^sup -^ channel. Strong hypertonic stress promptly induced a cytosolic Ca^sup 2+^ increase lasting >50 min together with sustained shrinkage and thereafter caspase-3 activation after 4 h. The hypertonic stress induced slight increases in [K^sup +^]^sub i^ and [Cl^sup -^]^sub i^ in the first 50 min, but these increases were much less than the effect of shrinkage-induced condensation, indicating that K^sup +^ and Cl^sup -^ efflux took place. Hypertonicity induced caspase-3 activation that was prevented not only by cytosolic Ca^sup 2+^ chelation but also by K^sup +^ and Cl^sup -^ channel blockers. Thus, it is concluded that not only Ca^sup 2+^ mobilization but early-phase efflux of K^sup +^ and Cl^sup -^ are required for caspase activation, and Ca^sup 2+^ mobilization is a downstream and resultant event of cell shrinkage in both staurosporine- and hypertonicity-induced apoptosis.[PUBLICATION ABSTRACT]

• Publisher: Springer Nature B.V
• Subject: Chelation