Inhibition of DNA fragmentation in thymocytes and isolated thymocyte nuclei by agents that stimulate protein kinase C

D. J. McConkey, P. Hartzell, M. Jondal, S. Orrenius

Research output: Contribution to journalArticlepeer-review

Abstract

Glucocorticoid hormones and Ca2+ ionophores stimulate a suicide process in immature thymocytes, known as apoptosis or programmed cell death, that involves extensive DNA fragmentation. We have recently shown that a sustained increase in cytosolic Ca2+ concentration stimulates DNA fragmentation and cell killing in glucocorticoid- or ionophore-treated thymocytes. However, a sustained increase in the cytosolic Ca2+ level also mediates lymphocyte proliferation, suggesting that apoptosis is blocked in proliferating thymocytes. In this study we report that phorbol esters, which selectively stimulate protein kinase C (PKC), blocked DNA fragmentation and cell death in thymocytes exposed to Ca2+ ionophore or glucocorticoid hormone. The T cell mitogen, concanavalin A, which stimulates thymocytes by a mechanism that involves PKC activation, caused concentration-dependent increases in the cytosolic Ca2+ level that did not result in DNA fragmentation, but incubation with concanavalin A and the PKC inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) resulted in both DNA fragmentation and cell death. Phorbol ester directly inhibited Ca2+-dependent DNA fragmentation in isolated thymocyte nuclei. Our results strongly suggest that PKC activation blocks thymocyte apoptosis by preventing Ca2+-stimulated endonuclease activation.

Original languageEnglish (US)
Pages (from-to)13399-13402
Number of pages4
JournalJournal of Biological Chemistry
Volume264
Issue number23
StatePublished - Jan 1 1989
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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