The Tumor Suppressor PTEN Positively Regulates Macroautophagy by Inhibiting the Phosphatidylinositol 3-Kinase/Protein Kinase B Pathway

doi:10.1074/jbc.C100319200

The Tumor Suppressor PTEN Positively Regulates Macroautophagy by Inhibiting the Phosphatidylinositol 3-Kinase/Protein Kinase B Pathway*

From the ^‡INSERM U504, Glycobiologie et Signalisation Cellulaire, 16 Avenue Paul-Vaillant-Couturier, 94807 Villejuif Cedex, France and the ^¶Department of Biochemistry, Academic Medical Centre University of Amsterdam, 1105AZ Amsterdam, The Netherlands

Abstract

The tumor suppressor PTEN is a dual protein and phosphoinositide phosphatase that negatively controls the phosphatidylinositol (PI) 3-kinase/protein kinase B (Akt/PKB) signaling pathway. Interleukin-13 via the activation of the class I PI 3-kinase has been shown to inhibit the macroautophagic pathway in the human colon cancer HT-29 cells. Here we demonstrate that the wild-type PTEN is expressed in this cell line. Its overexpression directed by an inducible promoter counteracts the interleukin-13 down-regulation of macroautophagy. This effect was dependent upon the phosphoinositide phosphatase activity of PTEN as determined by using the mutant G129E, which has only protein phosphatase activity. The role of Akt/PKB in the signaling control of interleukin-13-dependent macroautophagy was investigated by expressing a constitutively active form of the kinase (^MyrPKB). Under these conditions a dramatic inhibition of macroautophagy was observed. By contrast a high rate of autophagy was observed in cells expressing a dominant negative form of PKB. These data demonstrate that the signaling control of macroautophagy overlaps with the well known PI 3-kinase/PKB survival pathway and that the loss of PTEN function in cancer cells inhibits a major catabolic pathway.

Footnotes

↵* This work was supported by institutional funding from the INSERM and by grants from the Association pour la Recherche sur le Cancer (5831), Vaincre les Maladies Lysosomales, and the Ligue Nationale contre le Cancer. This work is part of a bilateral project of INSERM/NWO.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ Present address: Dept. of Biochemistry, Sciences II, University of Geneva, 30 quai Ernest Ansermet, 12114 Geneva, Switzerland.
↵‖ To whom correspondence should be addressed: INSERM U504, Glycobiologie et Signalisation Cellulaire, 16 Avenue Paul-Vaillant-Couturier, 94807 Villejuif Cedex, France. Tel.: 33-1-45-59-50-41; Fax: 33-1-46-77-02-33; E-mail: codogno@vjf.inserm.fr.
Published, JBC Papers in Press, July 26, 2001, DOI 10.1074/jbc.C100319200
↵2 S. Arico, A. Petiot, C. Bauvy, P. F. Dubbelhuis, A. J. Meijer, P. Codogno, and E. Ogier-Denis, unpublished data.
Abbreviations:

3-MA

3-methyladenine

Akt/PKB

protein kinase B

GSK-3β

glycogen synthase kinase-3β

HA

hemagglutinin

His

polyhistidine

IL

interleukin

IPTG

isopropyl-β-d-thiogalactopyranoside

kd

kinase dead

LDH

lactate dehydrogenase

Myr

myristoylated

PCR

polymerase chain reaction

PI 3-K

phosphatidylinositol 3-kinase

wt

wild-type
- Received June 12, 2001.
- Revision received July 13, 2001.
The American Society for Biochemistry and Molecular Biology, Inc.