Phosphoinositide 3‐phosphatase segregates from phosphatidylinositol 3‐kinase in EGF‐stimulated A431 cells and fails to in vitro hydrolyse phosphatidylinositol(3,4,5) tris phosphate

• Published in: FEBS letters Vol. 341; no. 1; pp. 113 - 118
• Main Authors: Payrastre, Bernard, Gironcel, Daisy, Plantavid, Monique, Mauco, Gérard, Breton, Monique, Chap, Hugues
• Format: Journal Article
• Language: English
• Published: 14.03.1994
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(94)80251-3

Beside 4‐ and 5‐phosphatases playing a role in the interconversion between the D‐3 phosphorylated polyphosphoinositides, the only enzyme described so far to be responsible for a phosphomonoesterasic activity on the D‐3 position of inositol lipids is a specific 3‐phosphatase that hydrolyzes PtdIns(3)P in NIH 3T3 cells. We report here the presence of a potent 3‐phosphatase activity in different cell types. This activity is detected both in cytosol and membranes of A431 cells and is inhibited by VO 4 3− and Zn 2+ . Interestingly, the cytosolic activity from A431 cells selectively hydrolyzes in vitro PtdIns(3)P and PtdIns(3,4)P 2 , whereas PtdIns(3,4,5)P 3 remains a very poor substrate under the same conditions. Finally, assays of phosphatidylinositol 3‐kinase and 3‐phosphatase activities in the pool of phosphotyrosine‐containing proteins isolated from EGF‐stimulated A431 cells suggest a compartmentation of these two antagonistic activities during cell activation.