Inhibition of antigen-receptor signaling by Platelet Endothelial Cell Adhesion Molecule-1 (CD31) requires functional ITIMs, SHP-2, and p56(lck).
Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31) is a 130-kd member of the immunoglobulin gene superfamily that is expressed on the surface of platelets, endothelial cells, myeloid cells, and certain lymphocyte subsets. PECAM-1 has recently been shown to contain functional immunoreceptor tyrosine-based inhibitory motifs (ITIMs) within its cytoplasmic domain, and co-ligation of PECAM-1 with the T-cell antigen receptor (TCR) results in tyrosine phosphorylation of PECAM-1, recruitment of Src homology 2 domain-containing protein tyrosine phosphatase-2 (SHP-2), and attenuation of TCR-mediated cellular signaling. To determine the molecular basis of PECAM-1 inhibitory signaling in lymphocytes, the study sought to (1) establish the importance of the PECAM-1 ITIMs for its inhibitory activity, (2) determine the relative importance of SHP-2 versus SHP-1 in mediating the inhibitory effect of PECAM-1, and (3) identify the protein tyrosine kinases required for PECAM-1 tyrosine phosphorylation in T cells. Co-ligation of wild-type PECAM-1 with the B-cell antigen receptor expressed on chicken DT40 B cells resulted in a marked reduction of calcium mobilization-similar to previous observations in T cells. In contrast, co-ligation of an ITIM-less form of PECAM-1 had no inhibitory effect. Furthermore, wild-type PECAM-1 was unable to attenuate calcium mobilization in SHP-2-deficient DT40 variants despite abundant levels of SHP-1 in these cells. Finally, PECAM-1 failed to become tyrosine phosphorylated in p56(lck)-deficient Jurkat T cells. Together, these data provide important insights into the molecular requirements for PECAM-1 regulation of antigen receptor signaling.
Newman
D K
DK
Blood Research Institute, The Blood Center of Southeastern Wisconsin, Milwaukee, WI 53233, USA. dknewman@bcsew.edu
Hamilton
C
C
Newman
P J
PJ
D020816:Amino Acid Motifs; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002645:Chickens; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells / Q000187:drug effects / Q000201:enzymology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000172:deficiency / Q000502:physiology*; D010766:Phosphorylation; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D054648:Protein Phosphatase 2; D011499:Protein Processing, Post-Translational; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D013329:Structure-Activity Relationship; D014162:Transfection; D018909:src Homology Domains
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D047908:Intracellular Signaling Peptides and Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D054648:Protein Phosphatase 2; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases