Src-family tyrosine kinase fyn phosphorylates phosphatidylinositol 3-kinase enhancer-activating Akt, preventing its apoptotic cleavage and promoting cell survival.
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Tang X, Feng Y, Ye K
Src-family tyrosine kinase fyn phosphorylates phosphatidylinositol 3-kinase enhancer-activating Akt, preventing its apoptotic cleavage and promoting cell survival.
Cell Death Differ. 2007 Feb;14(2):368-77. Epub 2006 Jul 14.
- PubMed ID
- 16841086 [ View in PubMed]
- Abstract
Phosphatidylinositol 3-kinase enhancer-activating Akt (PIKE-A) binds Akt and upregulates its kinase activity, preventing apoptosis. PIKE-A can be potently phosphorylated on tyrosine residues 682 and 774, leading to its resistance to caspase cleavage. However, the upstream tyrosine kinases responsible for PIKE-A phosphorylation and subsequent physiological significance remain unknown. Here, we show that PIKE-A can be cleaved by the active apoptosome at both D474 and D592 residues. Employing fyn-deficient mouse embryonic fibroblast cells and tissues, we demonstrate that fyn is essential for phosphorylating PIKE-A and protects it from apoptotic cleavage. Active but not kinase-dead fyn interacts with PIKE-A and phosphorylates it on both Y682 and Y774 residues. Tyrosine phosphorylation in PIKE-A is required for its association with active fyn but not for Akt. Mutation of D into A in PIKE-A protects it from caspase cleavage and promotes cell survival. Thus, this finding provides a molecular mechanism accounting for the antiapoptotic action of src-family tyrosine kinase.