Document Detail

Identification of potassium-dependent and -independent components of the apoptotic machinery in mouse ovarian germ cells and granulosa cells.
MedLine Citation:
PMID:  11058539     Owner:  NLM     Status:  MEDLINE    
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.
G I Perez; D V Maravei; A M Trbovich; J A Cidlowski; J L Tilly; F M Hughes
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biology of reproduction     Volume:  63     ISSN:  0006-3363     ISO Abbreviation:  Biol. Reprod.     Publication Date:  2000 Nov 
Date Detail:
Created Date:  2000-12-15     Completed Date:  2000-12-15     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0207224     Medline TA:  Biol Reprod     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1358-69     Citation Subset:  IM    
Vincent Center for Reproductive Biology, Department of Obstetrics and Gynecology, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts 02114, USA.
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MeSH Terms
Apoptosis / physiology*
Caspases / metabolism
Cell Nucleus / metabolism
Cytoplasm / metabolism
DNA / chemistry,  genetics
Deoxyribonuclease I / metabolism
Electrophoresis, Agar Gel
Electrophoresis, Gel, Pulsed-Field
Germ Cells / physiology*
Granulosa Cells / physiology*
In Situ Nick-End Labeling
Oocytes / physiology
Ovarian Follicle / cytology
Ovary / cytology,  physiology*
Plasmids / chemistry,  genetics
Potassium / physiology*
Rats, Sprague-Dawley
Grant Support
Reg. No./Substance:
7440-09-7/Potassium; 9007-49-2/DNA; EC I; EC 3.4.22.-/Caspases

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