P-selectin is acylated with palmitic acid and stearic acid at cysteine 766 through a thioester linkage

We report that the adhesion receptor P-selectin can be metabolically labeled with [³H]palmitic acid in human platelets. Analysis of alkaline methanolysis products from labeled protein demonstrated that the radioactivity associated with P-selectin was covalently bound palmitic acid. [³H]Palmitic acid was cleaved by hydroxylamine treatment at neutral pH and by reducing agents, indicating that acylation occurred through a thioester linkage. Both stearic acid and palmitic acid were detected by gas chromatography-mass spectrometry analysis of alkaline hydrolysates of purified P-selectin. Deletion or mutation of Cys⁷⁶⁶ eliminated [³H] palmitic acid labeling of P-selectin in transfected COS-7 cells. We conclude that the cytoplasmic domain of P-selectin is acylated at Cys⁷⁶⁶ through a thioester bond. Fatty acid acylation may regulate intracellular trafficking or other functions of P-selectin.