Regulation of apoptosis by phosphatidylinositol 4,5-bisphosphate inhibition of caspases, and caspase inactivation of phosphatidylinositol phosphate 5-kinases

Marisan Mejillano, Masaya Yamamoto, Andrew L. Rozelle, Hui Qiao Sun, Xiaodong Wang, Helen L. Yin

Research output: Contribution to journalArticle

69 Scopus citations

Abstract

Phosphoinositides such as phosphatidylinositol 3,4,5-trisphosphate and phosphatidylinositol 3,4-bisphosphate promote cell survival and protect against apoptosis by activating Akt/PKB, which phosphorylates components of the apoptotic machinery. We now report that another phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2) is a direct inhibitor of initiator caspases 8 and 9, and their common effector caspase 3. PIP2 inhibited procaspase 9 processing in cell extracts and in a reconstituted procaspase 9/Apaf1 apoptosome system. It inhibited purified caspase 3 and 8 activity, at physiologically attainable PIP2 levels in mixed lipid vesicles. Caspase 3 binding to PIP2 was confirmed by cosedimentation with mixed lipid vesicles. Overexpression of phosphatidylinositol phosphate 5-kinase α (PIP5KIα), which synthesizes PIP2, suppressed apoptosis, whereas a kinase-deficient mutant did not. Protection by the wild-type PIP5KIα was accompanied by decreases in the generation of activated caspases and of caspase 3-cleaved PARP. Protection was not mediated through PIP3 or Akt activation. An anti-apoptotic role for PIP2 is further substantiated by our finding that PIP5KIα was cleaved by caspase 3 during apoptosis, and cleavage inactivated PIP5KIα in vitro. Mutation of the P4 position (D279A) of the PIP5KIα caspase 3 cleavage consensus prevented cleavage in vitro, and during apoptosis in vivo. Significantly, the caspase 3-resistant PIP5KIα mutant was more effective in suppressing apoptosis than the wild-type kinase. These results show that PIP2 is a direct regulator of apical and effector caspases in the death receptor and mitochondrial pathways, and that PIP5KIα inactivation contributes to the progression of apoptosis. This novel feedforward amplification mechanism for maintaining the balance between life and death of a cell works through phosphoinositide regulation of caspases and caspase regulation of phosphoinositide synthesis.

Original languageEnglish (US)
Pages (from-to)1865-1872
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number3
DOIs
StatePublished - Jan 19 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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