Identification of potassium-dependent and -independent components of the apoptotic machinery in mouse ovarian germ cells and granulosa cells.

Published

Journal Article

Recent studies with thymocytes have suggested a critical role for intracellular potassium in the regulation of apoptosis. In this study, we examined the pathways of K(+) regulation during ovarian cell death. In initial studies, fluorographic analysis demonstrated a significant loss of K(+) during apoptosis stimulated by doxorubicin in oocytes and trophic hormone deprivation in granulosa cells. In oocytes, suppression of potassium efflux by potassium-enriched medium prevented condensation, budding, and fragmentation, although it did not block DNA degradation, suggesting the existence of potassium-independent nucleases in oocytes. Culture of granulosa cells in potassium-enriched medium inhibited internucleosomal DNA cleavage, although high-molecular weight DNA cleavage was apparent, suggesting that the nuclease or nucleases responsible for generating 50-kilobase (kb) fragments in these cells is potassium independent. To address this directly, isolated granulosa cell nuclei were stimulated to autodigest their DNA, and internucleosomal, but not large-fragment, cleavage was completely blocked by 150 mM potassium. We next examined whether the proapoptotic caspases are targets for potassium regulation. In cell-free assays, processing of pro-interleukin-1beta and proteolysis of cellular actin by recombinant caspase-1 and caspase-3, respectively, were suppressed by the presence of 150 mM potassium. Other monovalent ions (NaCl, LiCl) exerted a similar effect in these cell-free assays. Thus, in oocytes and granulosa cells, potassium efflux appears to occur early in the cell death program and may regulate a number of apoptotic events including caspase activity and internucleosomal DNA cleavage. However, there also exist novel potassium-independent pathways in both ovarian germ cells and somatic cells that signal certain apoptotic events, such as large-fragment DNA cleavage.

Full Text

Duke Authors

Cited Authors

  • Perez, GI; Maravei, DV; Trbovich, AM; Cidlowski, JA; Tilly, JL; Hughes, FM

Published Date

  • November 2000

Published In

Volume / Issue

  • 63 / 5

Start / End Page

  • 1358 - 1369

PubMed ID

  • 11058539

Pubmed Central ID

  • 11058539

International Standard Serial Number (ISSN)

  • 0006-3363

Digital Object Identifier (DOI)

  • 10.1095/biolreprod63.5.1358

Language

  • eng

Conference Location

  • United States