Differential association of cytoplasmic signalling molecules SHP‐1, SHP‐2, SHIP and phospholipase C‐γ1 with PECAM‐1/CD31

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Abstract
Recent studies have shown that, in addition to its role as an adhesion receptor, platelet endothelial cell adhesion molecule 1/CD31 becomes phosphorylated on tyrosine residues Y663 and Y686 and associates with protein tyrosine phosphatases SHP‐1 and SHP‐2. In this study, we screened for additional proteins which associate with phosphorylated platelet endothelial cell adhesion molecule 1, using surface plasmon resonance. We found that, besides SHP‐1 and SHP‐2, platelet endothelial cell adhesion molecule 1 binds the cytoplasmic signalling proteins SHIP and PLC‐γ1 via their Src homology 2 domains. Using two phosphopeptides, NSDVQpY663TEVQV and DTETVpY686SEVRK, we demonstrate differential binding of SHP‐1, SHP‐2, SHIP and PLC‐γ1. All four cytoplasmic signalling proteins directly associate with cellular platelet endothelial cell adhesion molecule 1, immunoprecipitated from pervanadate‐stimulated THP‐1 cells. These results suggest that overlapping immunoreceptor tyrosine‐based inhibition motif/immunoreceptor tyrosine‐based activation motif‐like motifs within platelet endothelial cell adhesion molecule 1 mediate differential interactions between the Src homology 2 containing signalling proteins SHP‐1, SHP‐2, SHIP and PLC‐γ1.