The Docking Molecule Gab2 Is Induced by Lymphocyte Activation and Is Involved in Signaling by Interleukin-2 and Interleukin-15 but Not Other Common γ Chain-using Cytokines

doi:10.1074/jbc.M004021200

The Docking Molecule Gab2 Is Induced by Lymphocyte Activation and Is Involved in Signaling by Interleukin-2 and Interleukin-15 but Not Other Common γ Chain-using Cytokines*

From the Lymphocyte Cell Biology Section, Arthritis and Rheumatism Branch, NIAMS, National Institutes of Health, Bethesda, Maryland 20892 and the ^§Division of Hematology-Oncology, Department of Medicine, Beth Israel-Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115

Abstract

Interleukin (IL)-2, a critical cytokine with indispensable functions in regulating lymphoid homeostasis, induces the activation of several biochemical pathways. Precisely how these pathways are linked and how they relate to the biological action of IL-2 is incompletely understood. We previously identified SHP-2 (Src homology 2 domain containing phosphatase 2) as an important intermediate in IL-2-dependent MAPK activation and showed its association with a 98-kDa phosphoprotein in response to IL-2. Here, we demonstrate that Gab2, a recently identified adapter molecule, is the major SHP-2 and phosphatidylinositol 3′-kinase-associated 98-kDa protein in normal, IL-2-activated lymphocytes. We further demonstrate that phosphorylation of both Gab2 and SHP-2 is largely dependent upon tyrosine 338 of the IL-2 receptor β chain. Gab2 can be a substrate of all the three major classes of non-receptor tyrosine kinases associated with the IL-2R, but in terms of IL-2 signaling, JAK3 but not Lck or Syk is essential for Gab2 phosphorylation. We also demonstrate that only IL-2 and IL-15, but not other γc cytokines induce Gab2 phosphorylation; the ability to phosphorylate Gab2 correlates with Shc phosphorylation and ERK1/ERK2 activation. Finally, we also show that Gab2 levels are regulated by T cell activation, and resting T cells express little Gab2. Therefore, up-regulation and activation of Gab2 may be important in linking the IL-2 receptor to activation of MAPK and may be an important means of achieving specificity in cytokine signaling.

Footnotes

↵* 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.

This paper is dedicated to the memory of Ernesto Gadina.
↵‡ To whom correspondence should be addressed: Bldg. 10, Rm. 9N228, 10 Center Dr. MSC 1820, Bethesda, MD 20892-1820. Tel.: 301-496-2541; Fax: 301-402-0012. E-mail: massimog@helix.nih.gov.
↵¶ Supported by National Research Service Award CA72144 from the National Institutes of Health as well as by an Anna D. Barker postdoctoral fellowship in basic science from American Association for Cancer Research.
↵‖ Recipient of National Institutes of Health Grant RO1-DK50693.
Published, JBC Papers in Press, June 9, 2000, DOI 10.1074/jbc.M004021200
↵2 Gu, H., Maeda, H., Moon, J. J., Lord, J. D., Yoakim, M., Nelson, B. H., and Neel, B. G. (2000) Mol. Cell Biol., in press.
↵3 W. E. Paul, personal communication.
Abbreviations:

IL-

interleukin-

IL-2R

IL-2 receptor

ERK

extracellular signal-regulated kinase

FRIP

IL-four receptor interactingprotein

γc

common γ chain

IFN

interferon

IRS

insulin receptor substrate

JAK

Janus kinase

MAPK

mitogen-activated protein kinase

NK

natural killer

SH2

Src homology 2

SHP-2

SH2 domain containing phosphatase 2

PI 3′-kinase

phosphatidylinositol 3′-kinase

STAT

signal transducer and activator of transcription

IU

international unit

PHA

phytohemagglutinin
- Received May 11, 2000.
- Revision received May 31, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.