Rack1, a Receptor for Activated Protein Kinase C, Interacts with Integrin β Subunit

doi:10.1074/jbc.273.4.2379

Rack1, a Receptor for Activated Protein Kinase C, Interacts with Integrin β Subunit*

Joanna Liliental and
David D. Chang‡

From the Department of Medicine, Microbiology and Immunology, and Jonsson Cancer Center, University of California at Los Angeles School of Medicine, Los Angeles, California 90095

Abstract

The integrin β subunit cytoplasmic domains are important for activation-dependent cell adhesion and adhesion-dependent signaling events. We report an interaction between integrin β subunit cytoplasmic domain and Rack1, a Trp-Asp (WD) repeat protein that has been shown to bind activated protein kinase C. The Rack1-binding site on integrin β₂subunit resides within a conserved, membrane-proximal region. In the yeast two-hybrid assay, WD repeats five to seven of Rack1 (Rack1-WD5/7) interact with integrin β₁, β₂, and β₅ cytoplasmic domain. In eukaryotic cells, Rack1 co-immunoprecipitates with at least two different β integrins, β₁ integrins in 293T cells and β₂ integrins in JY lymphoblastoid cells. Whereas Rack1-WD5/7 binds integrins constitutively, the association of full-length Rack1 to integrinsin vivo requires a treatment with phorbol esters, which promotes cell spreading and adhesion. These findings suggest that Rack1 may link protein kinase C directly to integrins and participate in the regulation of integrin functions.

Footnotes

↵* This work was supported by the grants from the Margaret E. Early Medical Research Trust, the Searle Scholars Program/The Chicago Community Trust, the James S. McDonnell Foundation, and the Jonsson Cancer Center and by Tumor Immunology Training Grant CA09120-21.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.
↵‡ To whom correspondence should be addressed: UCLA School of Medicine, Div. of Heme-Onc, Factor 11-934, 10833 Le Conte Ave., Los Angeles, CA 90095. Fax: 310-825-6192; E-mail:dchang{at}medicine.medsch.ucla.edu.
↵1 The abbreviations used are: LFA1, leukocyte function antigen-1; GST, glutathione S-transferase; PKC, protein kinase C; PMA, phorbol 12-myristate 13-acetate; mAb, monoclonal antibody(ies); GST-Rack1, GST-tagged Rack1; WD, Trp-Asp.
- Received July 18, 1997.
- Revision received October 11, 1997.
The American Society for Biochemistry and Molecular Biology, Inc.