20-HETE Signals Through G Protein-Coupled Receptor GPR75 (Gq) to Affect Vascular Function and Trigger Hypertension
Rationale: 20-Hydroxyeicosatetraenoic acid (20-HETE), one of the principle cytochrome P450 (CYP) eicosanoids, is a potent vasoactive lipid whose vascular effects include stimulation of smooth muscle contractility, migration and proliferation, as well as endothelial cell dysfunction and inflammation. Increased levels of 20-HETE in experimental animals and in humans are associated with hypertension, stroke, myocardial infarction and vascular diseases.
Objective: To date, a receptor/binding site for 20-HETE has been implicated based on the use of specific agonists and antagonists. The present study was undertaken to identify a receptor to which 20-HETE binds and through which it activates a signaling cascade that culminates in many of the functional outcomes attributed to 20-HETE in vitro and in vivo.
Methods and Results: Using crosslinking analogs, click chemistry, binding assays, and functional assays, we identified GPR75, currently an orphan G-protein coupled receptor (GPCR), as a specific target of 20-HETE. In cultured human endothelial cells, 20-HETE binding to GPR75 stimulated Gαq/11 protein dissociation and increased inositol phosphate (IP-1) accumulation as well as GPCR-kinase interacting protein-1 (GIT1)-GPR75 binding, which further facilitated the c-Src-mediated transactivation of endothelial EGFR. This results in downstream signaling pathways which induce angiotensin-converting enzyme (ACE) expression and endothelial dysfunction. Knockdown of GPR75 or GIT1 prevented 20-HETE-mediated endothelial growth factor receptor (EGFR) phosphorylation and ACE induction. In vascular smooth muscle cells, GPR75-20-HETE pairing is associated with Gαq/11- and GIT1-mediated protein kinase C (PKC)-stimulated phosphorylation of MaxiKβ, linking GPR75 activation to 20-HETE-mediated vasoconstriction. GPR75 knockdown in a mouse model of 20-HETE-dependent hypertension prevented blood pressure elevation and 20-HETE-mediated increases in ACE expression, endothelial dysfunction, smooth muscle contractility and vascular remodeling.
Conclusions: This is the first report to identify a GPCR target for an eicosanoid of this class. The discovery of 20-HETE-GPR75 pairing presented here provides the molecular basis for the signaling and pathophysiological functions mediated by 20-HETE in hypertension and cardiovascular diseases.
- Received December 21, 2016.
- Revision received March 3, 2017.
- Accepted March 20, 2017.