Inhibition of protein palmitoylation, raft localization, and T cell signaling by 2-bromopalmitate and polyunsaturated fatty acids

The ability of the Src family kinases Fyn and Lck to participate in signali ng through the T cell receptor is critically dependent on their dual fatty acylation with myristate and palmitate. Here we identify a palmitate analog , 2-bromopalmitate, that effectively blocks Fyn fatty acylation in general and palmitoylation in particular. Treatment of COS-1 cells with 2-bromopalm itate blocked myristoylation and palmitoylation of Fyn and inhibited membra ne binding and localization of Fyn to detergent-resistant membranes (DRMs), In Jurkat T cells, 2-bromopalmitate blocked localization of the endogenous palmitoylated proteins Fyn, Lck, and LAT to DRMs. This resulted in impaire d signaling through the T cell receptor as evidenced by reductions in tyros ine phosphorylation, calcium release, and activation of mitogen-activated p rotein kinase. We also examined the ability of long chain polyunsaturated f atty acids (PUFAs) to inhibit protein fatty acylation, PUFAs have been repo rted to inhibit T cell signaling by excluding Src family kinases from DRMs. Here we show that the PUFAs arachidonic acid and eicosapentaenoic acid inh ibit Fyn palmitoylation and consequently block Fyn localization to DRMs, We propose that inhibition of protein palmitoylation represents a novel mecha nism by which PUFAs exert their immunosuppressive effects.