Platelet-Endothelial Cell Adhesion Molecule-1 (CD31), a Scaffolding Molecule for Selected Catenin Family Members Whose Binding Is Mediated by Different Tyrosine and Serine/Threonine Phosphorylation

Abstract

Platelet-endothelial cell adhesion molecule (PE-CAM)-1 is a 130-kDa glycoprotein commonly used as an endothelium-specific marker. Evidence to date suggests that PECAM-1 is more than just an endothelial cell marker but is intimately involved in signal transduction pathways. This is mediated in part by phosphorylation of specific tyrosine residues within the ITAM domain of PECAM-1 and by recruitment of adapter and signaling molecules. Recently we demonstrated that PECAM-1/␤-catenin association functions to regulate ␤-catenin localization and, moreover, to modulate ␤-catenin tyrosine phosphorylation levels. Here we show that: 1) not only ␤-catenin, but also ␥-catenin is associated with PE-CAM-1 in vitro and in vivo; 2) PKC enzyme directly phosphorylates purified PECAM-1; 3) PKC-derived PECAM-1 serine/threonine phosphorylation inversely correlates with ␥-catenin association; 4) PECAM-1 recruits ␥-catenin to cell-cell junctions in transfected SW480 cells; and 5) ␥-catenin may recruit PECAM-1 into an insoluble cytoskeletal fraction. These data further support the concept that PECAM-1 functions as a binder and modulator of catenins and provides a molecular mechanism for previously reported PECAM-1/cytoskeleton interactions.Platelet-endothelial cell adhesion molecule (PECAM-1, CD31) 1 is a 130-kDa glycoprotein belonging to the Ig superfamily of cell adhesion molecules. PECAM-1 expression is restricted to cells of the vascular system platelets, monocytes, neutrophils, selected T cells, and endothelial cells (1). In the latter, PECAM-1 is localized to cell-cell borders of confluent monolayers and, in addition, to lumen-facing areas of blood vessels or tube-like endothelial structures formed in vitro (2). PECAM-1 becomes diffusely distributed on the cell surface of sparse cell cultures or at the leading fronts of migrating cells (3). PECAM-1 has been shown to be a key player in the adhesion cascade leading to extravasation of leukocytes during inflammation. Pretreatment of monocytes or neutrophils, as well as endothelial cells, with anti-PECAM-1 antibodies effectively inhibited transmigration in vitro (4) and in vivo (5), indicating that PECAM-1 molecules on both the endothelial cells and the leukocytes contribute to the transmigration process. This was further supported by a genetic approach in PECAM-1 knockout mice, in which leukocytes are transiently arrested between the vascular endothelium and the basement membrane of inflammatory sites (6). In addition, PECAM-1 knockout mice have been noted to suffer from prolonged bleeding times, which is at least in part due to disrupted endothelial-platelet interactions (53), supporting the role of PECAM-1 as mediator of cell adhesion/activation. PECAM-1 has been shown to be more than just a passive player in adhesive interactions and indeed is actively involved in signal transduction pathways. PECAM-1 was demonstrated to undergo phosphorylation on tyrosine residues following mechanical (7) or biochemical (8 -10) stimulation. Specifically, an immunoreceptor tyrosine-based activati...

MAPKs (ERK½, p38) and AKT Can Be Phosphorylated by Shear Stress Independently of Platelet Endothelial Cell Adhesion Molecule-1 (CD31) in Vascular Endothelial Cells

“…An ITAM (immunoreceptor tyrosine-based activation motif) domain, encoded by exons 12, 13, and 14, has been identified in the cytoplasmic tail of PECAM-1 (19). PECAM-1 has been noted to be phosphorylated by fluid flow and osmotic shock and also to associate with adapter and signaling molecules in an ITAM-independent manner, as was recently shown for ␤-catenin (20), ␥-catenin (21), and STAT (signal transducers and activators of transcription) (22) family members. Functionally, PECAM-1 tyrosine phosphorylation has been shown to play a role in endothelial cell migration and angiogenesis (23,24).…”

The role of endothelial glycocalyx components in mechanotransduction of fluid shear stress

“…Syndecans that contain both HS and CS have an established association with the cytoskeleton [19], and through it can decentralize the signal by distributing it to multiple sites within the cell (i.e., nucleus, organelles, focal adhesions, intercellular junctions). Significantly, the platelet-endothelial cell adhesion molecule (PECAM-1) associates with the cytoskeleton through catenins, and has been linked to shearinduced eNOS activation [20][21][22]. In terms of central transduction, it is noteworthy that glypicans which contain HS, but not CS, are linked to caveolae where eNOS resides along with many other signaling molecules [3].…”

Statin‐inhibited endothelial permeability could be associated with its effect on PECAM‐1 in endothelial cells

“…For example, during thrombin-induced platelet aggregation, PECAM-1 partitions with the Triton-insoluble cytoskeleton increased from 10% to 60% of total cellular PECAM-1 [33]. In confluent endothelial cells, 20% to 30% of PECAM-1 was found associated with the cytoskeleton [31,34] and it increased to 65% during cell migration [31].…”

“…A functional relationship between PECAM-1 and the cytoskeleton is being recognized as growing evidence has showed that PE-CAM-1 associates both physically and functionally with the underlying cytoskeleton [30,31]. It has been reported that the reorganization of actin cytoskeleton (stress fiber formation), and redistribution of a group of endothelial cell tight junction proteins from the TX-100-soluble to the TX-100-insoluble fractions are associated with transendothelial permeability in brain endothelial cells [32].…”