Cluster of differentiation (CD31
), Platelet Endothelial Cell Adhesion Molecule 1 (PECAM-1), is a 30kDa type I transmembrane glycoprotein expressed by endothelial cells
, platelets, leukocytes and some lymphocytes (e.g., B and T-cell subsets). Structurally, PECAM-1 consists of six extracellular immunoglobulin-like domains which serve to support various functions including homophilic binding, maintaining high expression of PECAM-1 within endothelial intercellular junctions, and supporting endothelial cell migration (1,2). PECAM's homophilic binding underscores its role in vascular barrier integrity and leukocyte trans-endothelial movement. However, PECAM may also engage in heterophilic interactions with molecules such as glycosaminoglycans (GAG), integrin alpha 5 beta 3
in lymphocytes and CD177/PR3
in neutrophils (2).
PECAM's intracellular cytoplasmic domain consists of a sequence of 118 amino acids and contains serine and tyrosine (also referred to as immunoreceptor tyrosine-based inhibitory motifs-ITIMs) residues, which may be phosphorylated upon cellular stimulation (3). ITIMs are phosphorylated by Src-family kinases and non-Src family kinases (e.g., Csk), leading to a conformational change which supports interactions with Src homology 2 (SH2) domain containing proteins such as protein-tyrosine phosphatase, SHP-2
(1,2). Formation of SHP-2/PECAM-1 complexes induces endothelial cell migration through the dephosphorylation of focal adhesion kinase and regulation of RhoA
activity (1). Signaling downstream of ITIM tyrosine phosphorylations also plays a role in PECAM's anti-apoptotic
activity, a function which is independent of its interaction with SHP-2. In platelets and leukocytes, phosphorylation of PECAM's cytosolic domain is inhibitory, preventing their activation.
1. Lertkiatmongkol, P., Liao, D., Mei, H., Hu, Y., & Newman, P. J. (2016). Endothelial functions of PECAM-1 (CD31). Current Opinion in Hematology. https://doi.org/10.1097/MOH.0000000000000239.Endothelial
2. Privratsky, J. R., & Newman, P. J. (2014). PECAM-1: Regulator of endothelial junctional integrity. Cell and Tissue Research. https://doi.org/10.1007/s00441-013-1779-3
3. Newman, P. J., & Newman, D. K. (2003). Signal transduction pathways mediated by PECAM-1: New roles for an old molecule in platelet and vascular cell biology. Arteriosclerosis, Thrombosis, and Vascular Biology. https://doi.org/10.1161/01.ATV.0000071347.69358.D9