Platelet endothelial cell adhesion molecule-1 (PECAM-1) homophilic adhesion is mediated by immunoglobulin-like domains 1 and 2 and depends on the cytoplasmic domain and the level of surface expression.
PECAM-1/CD31 is vascular cell adhesion and signaling molecule of the Ig superfamily that plays a role in neutrophil recruitment at inflammatory sites and may be involved the release of leukocytes from the bone marrow and in cardiovascular development. The interactions of PECAM-1 with its ligands are complex in that it is able to bind both with itself (homophilic adhesion) or with non-PECAM-1 ligands (heterophilic adhesion). Although the factors that regulate ligand binding are not fully understood, these interactions are regulated in part by its large cytoplasmic domain, a region of 118 amino acids encoded by 8 exons of its gene (exons 9-16). The purpose of this work was to better define the mechanisms of PECAM-1-dependent homophilic adhesion by analyzing the binding interactions of L-cells expressing full-length and selectively mutated forms of human, murine, and human/murine chimeric PECAM-1 molecules in an established aggregation assay. These studies demonstrate that 1) the minimal length of the cytoplasmic domain required for cellular aggregation is represented within the sequences encoded by exons 9 and 10, 2) removal or addition of the sequences encoded by exon 14 from the cytoplasmic domain can determine whether the mechanism of aggregation is a heterophilic calcium-dependent process or a homophilic calcium-independent process, 3) high levels of surface expression of PECAM-1 on the cell surface change the mechanism of aggregation from heterophilic to homophilic, and 4) PECAM-1-dependent homophilic binding appears to involve the direct interaction of only the first two extracellular Ig-like domains. These data suggest that PECAM-1-ligand interactions can be regulated through multiple pathways including alterations of the cytoplasmic domain and the level of surface expression.
Sun
J
J
Department of Medicine, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104-4283, USA.
Williams
J
J
Yan
H C
HC
Amin
K M
KM
Albelda
S M
SM
DeLisser
H M
HM
D000818:Animals; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002449:Cell Aggregation; D003593:Cytoplasm / Q000737:chemistry; D005091:Exons; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D007739:L Cells; D051379:Mice; D015394:Molecular Structure; D009154:Mutation; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D017384:Sequence Deletion; D014162:Transfection
D015214:Antigens, Differentiation, Myelomonocytic; D015815:Cell Adhesion Molecules; D007136:Immunoglobulins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011993:Recombinant Fusion Proteins