PECAM-1/CD31 trans-homophilic binding at the intercellular junctions is independent of its cytoplasmic domain; evidence for heterophilic interaction with integrin alphavbeta3 in Cis.
PECAM-1/CD31 is a cell adhesion and signaling molecule that is enriched at the endothelial cell junctions. Alternative splicing generates multiple PECAM-1 splice variants, which differ in their cytoplasmic domains. It has been suggested that the extracellular ligand-binding property, homophilic versus heterophilic, of these isoforms is controlled by their cytoplasmic tails. To determine whether the cytoplasmic domains also regulate the cell surface distribution of PECAM-1 splice variants, we examined the distribution of CD31-EGFPs (PECAM-1 isoforms tagged with the enhanced green fluorescent protein) in living Chinese hamster ovary cells and in PECAM-1-deficient endothelial cells. Our results indicate that the extracellular, rather than the cytoplasmic domain, directs PECAM-1 to the cell-cell borders. Furthermore, coculturing PECAM-1 expressing and deficient cells along with transfection of CD31-EGFP cDNAs into PECAM-1 deficient cells reveal that this PECAM-1 localization is mediated by homophilic interactions. Although the integrin alphavbeta3 has been shown to interact with PECAM-1, this trans-heterophilic interaction was not detected at the borders of endothelial cells. However, based on cocapping experiments performed on proT cells, we provide evidence that the integrin alphavbeta3 associates with PECAM-1 on the same cell surface as in a cis manner.
Wong
C W
CW
Department of Pathology, Centre Médical Universitaire, 1211 Geneva 4, Switzerland.
Wiedle
G
G
Ballestrem
C
C
Wehrle-Haller
B
B
Etteldorf
S
S
Bruckner
M
M
Engelhardt
B
B
Gisler
R H
RH
Imhof
B A
BA
D017398:Alternative Splicing; D000818:Animals; D016466:CHO Cells; D002196:Capillaries / Q000166:cytology / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D002560:Cerebrovascular Circulation; D006224:Cricetinae; D003593:Cytoplasm / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology* / Q000648:ultrastructure; D005091:Exons; D049452:Green Fluorescent Proteins; D007365:Intercellular Junctions / Q000502:physiology*; D008164:Luminescent Proteins / Q000032:analysis; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation; D019030:Receptors, Vitronectin / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
D008164:Luminescent Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D019030:Receptors, Vitronectin; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins