The Protein-tyrosine Phosphatase SHP-2 Binds Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1) and Forms a Distinct Signaling Complex during Platelet Aggregation

doi:10.1074/jbc.272.11.6986

The Protein-tyrosine Phosphatase SHP-2 Binds Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1) and Forms a Distinct Signaling Complex during Platelet Aggregation

EVIDENCE FOR A MECHANISTIC LINK BETWEEN PECAM-1- AND INTEGRIN-MEDIATED CELLULAR SIGNALING*

From the ^‡ Blood Research Institute, Blood Center of Southeastern Wisconsin, Milwaukee, Wisconsin 53233-2121 and the
^§ Departments of Cellular Biology and Pharmacology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226

^¶ Established Investigator of the American Heart Association. To whom correspondence should be addressed:
Blood Research Inst., The Blood Center of Southeastern Wisconsin, 638 N. 18th St., Milwaukee, WI 53233-2121.
Tel.: 414-937-6237; Fax: 414-937-6284.

Abstract

Platelet/endothelial cell adhesion molecule-1 (PECAM-1) is a homophilic adhesion receptor that mediates leukocyte/endothelial cell interactions that take place during transendothelial migration. Recent reports have shown that the binding of certain anti-PECAM-1 antibodies results in up-regulation of integrin function on the surface of leukocytes and platelets, suggesting that PECAM-1 may be capable of transmitting information into the cell following its engagement. PECAM-1 isolated from resting or activated but nonaggregated platelets was phosphorylated predominantly on serine residues; however, PECAM-1 derived from activated, aggregated platelets was strongly phosphorylated on tyrosine. Synthetic tyrosine-phosphorylated peptides derived from five different regions within the cytoplasmic domain of PECAM-1 were screened for their ability to associate with cytoplasmic signaling molecules. The protein-tyrosine phosphatase SHP-2 was found to interact specifically with two different PECAM-1 phosphopeptides containing highly conserved phosphatase-binding motifs on PECAM-1 with the sequences VQpY⁶⁶³TEV and TVpY⁶⁸⁶SEV. More important, SHP-2 bound not only PECAM-1 phosphopeptides, but also became associated with full-length cellular PECAM-1 during the platelet aggregation process, and this interaction was mediated by the amino-terminal Src homology 2 domains of the phosphatase. Since SHP-2 normally serves as a positive regulator of signal transduction, its association with activated PECAM-1 suggests a number of potential mechanisms by which PECAM-1 engagement might be coupled to integrin activation in vascular cells.

Footnotes

↵* This work was supported by Grants HL-44612 and HL-40926 (to P. J. N.) from the National Institutes of Health and Grants 96F-Post-34 (to D. E. J.), 96F-Post-49 (to C. M. W.), and 95F-Pre-16 (to R. W.) from the American Heart Association, Wisconsin Affiliate. This work was presented in abstract form at the 38th Annual Meeting of the American Society of Hematology, Orlando, FL, December 6-10, 1996. 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:

PECAM-1

platelet/endothelial cell adhesion molecule-1

SH2

Src homology 2

GST

glutathione S-transferase

TEMED

N,N,N′,N′-tetramethylethylenediamine

TRAP

thrombin receptor-activating peptide

PAGE

polyacrylamide gel electrophoresis

Fmoc

N-(9-fluorenyl)methoxycarbonyl.
↵² D. E. Jackson and P. J. Newman, unpublished observations.
- Received October 2, 1996.
- Revision received January 7, 1997.