Oxidative stress inhibits caveolin-1 palmitoylation and trafficking in endothelial cells

Abstract

During normal and pathological conditions, endothelial cells (ECs) are subjected to locally generated reactive oxygen species, produced by themselves or by other vessel wall cells. In excess these molecules cause oxidative injury to the cell but at moderate levels they might modulate intracellular signalling pathways. We have investigated the effect of oxidative stress on the palmitoylation and trafficking of caveolin-1 in bovine aortic ECs. Exogenous H2O2 did not alter the intracellular localization of caveolin-1 in ECs. However, metabolic labelling experiments showed that H2O2 inhibited the trafficking of newly synthesized caveolin-1 to membrane raft domains. Several mechanisms potentially responsible for this inhibition were examined. Impairment of caveolin-1 synthesis by H2O2 was not responsible for diminished trafficking. Similarly, the inhibition was independent of H2O2-induced caveolin-1 phosphorylation as shown by the markedly different concentration dependences. We tested the effect of H2O2 on palmitoylation of caveolin-1 by the incorporation of [3H]palmitic acid. Exposure of ECs to H2O2 markedly inhibited the palmitoylation of caveolin-1. Comparable inhibition was observed after treatment of cells with H2O2 delivered either as a bolus or by continuous delivery with glucose and glucose oxidase. Kinetic studies showed that H2O2 did not alter the rate of caveolin-1 depalmitoylation but instead decreased the ‘on-rate’ of palmitoylation. Together these results show for the first time the modulation of protein palmitoylation by oxidative stress, and suggest a cellular mechanism by which stress might influence caveolin-1-dependent cell activities such as the concentration of signalling proteins and cholesterol trafficking.

PTOV1 Enables the Nuclear Translocation and Mitogenic Activity of Flotillin-1, a Major Protein of Lipid Rafts

“…Palmitoylation is a reversible modification of proteins that can regulate the localization of proteins in membranes (25,43). Proteins with palmitoylable cysteine residues can cycle between palmitoylated and depalmitoylated states in response to a number of signals, including agonist-induced receptor activation and oxidative stress (11,22,32,33,43). It is not known if flotillin-1 can undergo such cycles of acylation-deacylation under physiological conditions, with associated cycles in its subcellular localization.…”

Correlated Endothelial Caveolin Overexpression and Increased Transcytosis in Experimental Diabetes

“…None of these fenestrations was observed in the microvasculature of our diabetic rats. In addition, the oxidative stress present in diabetes and known to activate the production of VEGF (Chua et al 1998) was reported to inhibit caveolin palmitoylation and therefore its association with the membrane (Parat et al 2002).…”

Oxidative Stress Reprograms Lipopolysaccharide Signaling via Src Kinase-dependent Pathway in RAW 264.7 Macrophage Cell Line

“…One might speculate that oxidative stress alters lipid rafts such that different molecules are recruited to the LPS signaling complex and initiate alternate pathways. In this regard, Parat and colleagues (29) recently demonstrated that oxidative stress was able to inhibit calveolin-1 palmitoylation and trafficking in endothelial cells. Because calveolae may play a role in sequestration of glycosylphosphatidylinositol-linked proteins such as CD14, inhibition of calveolin-1 by oxidant stress may interfere with classical LPS signaling (i.e.…”