Endothelial Palmitoylation Cycling Coordinates Vessel Remodeling in Peripheral Artery Disease.

RATIONALE

Peripheral artery disease, common in metabolic syndrome and diabetes mellitus, responds poorly to medical interventions and is characterized by chronic vessel immaturity leading to lower extremity amputations.

OBJECTIVE

To define the role of reversible palmitoylation at the endothelium in the maintenance of vascular maturity.

METHODS AND RESULTS

Endothelial knockout of the depalmitoylation enzyme APT-1 (acyl-protein thioesterase 1) in mice impaired recovery from chronic hindlimb ischemia, a model of peripheral artery disease. Endothelial APT-1 deficiency decreased fibronectin processing, disrupted adherens junctions, and inhibited in vitro lumen formation. In an unbiased palmitoylation proteomic screen of endothelial cells from genetically modified mice, R-Ras, known to promote vessel maturation, was preferentially affected by APT-1 deficiency. R-Ras was validated as an APT-1 substrate, and click chemistry analyses demonstrated increased R-Ras palmitoylation in cells with APT-1 deficiency. APT-1 enzyme activity was decreased in endothelial cells from mice. Hyperglycemia decreased APT-1 activity in human umbilical vein endothelial cells, due, in part, to altered acetylation of the APT-1 protein. Click chemistry analyses demonstrated increased R-Ras palmitoylation in the setting of hyperglycemia. Altered R-Ras trafficking, increased R-Ras palmitoylation, and fibronectin retention were found in diabetes mellitus models. Loss of R-Ras depalmitoylation caused by APT-1 deficiency constrained R-Ras membrane trafficking, as shown by total internal reflection fluorescence imaging. To rescue cellular phenotypes, we generated an R-Ras molecule with an inserted hydrophilic domain to circumvent membrane rigidity caused by defective palmitoylation turnover. This modification corrected R-Ras membrane trafficking, restored fibronectin processing, increased adherens junctions, and rescued defective lumen formation induced by APT-1 deficiency.

CONCLUSIONS

These results suggest that endothelial depalmitoylation is regulated by the metabolic milieu and controls plasma membrane partitioning to maintain vascular homeostasis.