The Related Adhesion Focal Tyrosine Kinase Is Tyrosine-phosphorylated after β1-Integrin Stimulation in B Cells and Binds to p130cas

doi:10.1074/jbc.272.1.228

The Related Adhesion Focal Tyrosine Kinase Is Tyrosine-phosphorylated after β1-Integrin Stimulation in B Cells and Binds to p130^cas*

From the ^‡ Division of Hematologic Malignancies, Dana-Farber Cancer Institute, and
the ^§ Division of Hematology and Oncology, Deaconess Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

^¶ To whom correspondence should be addressed:
Division of Hematologic Malignancies, Dana-Farber Cancer Institute, 44 Binney St., Boston, MA 02115.
Tel.: 617-632-3441; Fax: 617-632-5167.

Abstract

Integrin ligation initiates intracellular signaling events, among which are the activation of protein tyrosine kinases. The related adhesion focal tyrosine kinase (RAFTK), also known as PYK2 and CAKβ, is a tyrosine kinase that is homologous to the focal adhesion kinase (FAK) p125^FAK. The structure of RAFTK is similar to p125^FAK in that it lacks a transmembrane region, does not contain Src homology 2 or 3 domains, and has a proline-rich region in its C terminus. Here we report that RAFTK is a target for β1-integrin-mediated tyrosine phosphorylation in both transformed and normal human B cells. Ligation of the B cell antigen receptor also induced tyrosine phosphorylation of RAFTK. Phosphorylation of RAFTK following integrin- or B cell antigen receptor-mediated stimulation was decreased by prior treatment of cells with cytochalasin B, indicating that this process was at least partially cytoskeleton-dependent. One of the tyrosine-phosphorylated substrates after integrin stimulation in fibroblasts is p130^cas, which can associate with p125^FAK. RAFTK also interacted constitutively with p130^cas in B cells, since p130^cas was detected in RAFTK immunoprecipitates. Although the function of RAFTK remains unknown, these data suggest that RAFTK may have a significant function in integrin-mediated signaling pathways in B cells.

Footnotes

↵* This work was supported in part by National Institutes of Health Grants CA55207, CA66996, HL51456, HL55445, and HL46668, American Cancer Society Grant DHP-145, and a fellowship from the Lymphoma Foundation of America (to S. N. M.). 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.
↵¹ The abbreviations used are:

FAK

focal adhesion kinase

RAFTK

related adhesion focal tyrosine kinase

BCR

B cell antigen receptor

RαM

rabbit anti-mouse

TCR

T cell antigen receptor

SH

Src homology

TBS-T

Tris-buffered saline and Tween 20

mAb

monoclonal antibody

CB

cytochalasin B.
↵²S. N. Manié, A. R. P. Beck, A. Astier, S. F. Law, T. Canty, H. Hirai, B. J. Druker, H. Avraham, M. Sattler, R. Salgia, J. D. Griffin, E. A. Golemis, and A. S. Freedman, submitted for publication.
- Received April 27, 1996.
- Revision received October 15, 1996.