APC/Cdh1 targets PECAM-1 for ubiquitination and degradation in endothelial cells.

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a member of the immunoglobulin superfamily and is expressed by hematopoietic and endothelial cells (ECs). Recent studies have shown that PECAM-1 plays a crucial role in promoting the development of the EC inflammatory response in the context of disturbed flow. However, the mechanistic pathways that control PECAM-1 protein stability remain largely unclear. Here, we identified PECAM-1 as a novel substrate of the APC/Cdh1 E3 ubiquitin ligase. Specifically, lentivirus-mediated Cdh1 depletion stabilized PECAM-1 in ECs. Conversely, overexpression of Cdh1 destabilized PECAM-1. The proteasome inhibitor MG132 blocked Cdh1-mediated PECAM-1 degradation. In addition, Cdh1 promoted K48-linked polyubiquitination of PECAM-1 in a destruction box-dependent manner. Furthermore, we demonstrated that compared with pulsatile shear stress (PS), oscillatory shear stress decreased the expression of Cdh1 and the ubiquitination of PECAM-1, therefore stabilizing PECAM-1 to promote inflammation in ECs. Hence, our study revealed a novel mechanism by which fluid flow patterns regulate EC homeostasis via Cdh1-dependent ubiquitination and subsequent degradation of PECAM-1.

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