PECAM-1 shedding during apoptosis generates a membrane-anchored truncated molecule with unique signaling characteristics.
Shedding of cell surface molecules, including growth factor receptors, provides a mechanism by which cells regulate signal transduction events. Here we show that platelet-endothelial cell adhesion molecule (PECAM)-1 is shed from the endothelial cell surface during apoptosis and accumulates in the culture medium as a approximately 100 kDa soluble protein. The cleavage mediating the shedding is matrix metalloproteinase (MMP) dependent, as GM6001, a broad-spectrum MMP inhibitor, inhibits PECAM-1 accumulation in the culture medium in a dose-responsive manner. In addition to the 100 kDa soluble fragment, PECAM-1 cleavage generates the formation of a truncated (Tr.) approximately 28 kDa molecule, composed of the transmembrane and the cytoplasmic PECAM-1 domains. Transfections of the full-length (Fl) and the Tr. PECAM-1 gene constructs into endothelial and nonendothelial cells were performed. We found 1) significantly more gamma-catenin and SHP-2 bound to the truncated than to the full-length PECAM-1; 2) stable expression of the truncated PECAM-1 in SW480 colon carcinoma cells resulted in a dramatic decrease in cell proliferation, whereas expression of comparable levels of the full-length PECAM-1 had no effect; 3) the decrease observed in cell proliferation is due, in part, to an increase in programmed cell death (apoptosis) and correlated with continuous caspase 8 cleavage and p38/JNK phosphorylation. These results support the intimate involvement of PECAM-1 in signal transduction cascades and also suggest that caspase substrates (e.g., PECAM-1) may possess distinct and unique functions on cleavage.
Ilan
N
N
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Mohsenin
A
A
Cheung
L
L
Madri
J A
JA
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001792:Blood Platelets / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D002455:Cell Division; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D003110:Colonic Neoplasms; D003470:Culture Media; D004151:Dipeptides / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins
D000590:Amino Acid Chloromethyl Ketones; D015703:Antigens, CD; D003470:Culture Media; D004151:Dipeptides; D004791:Enzyme Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D020169:Caspases