Increased AT receptor expression mediates vasoconstriction leading to hypertension in Snx1 mice.

Angiotensin II type 1 receptor (ATR) is a vital therapeutic target for hypertension. Sorting nexin 1 (SNX1) participates in the sorting and trafficking of the renal dopamine D receptor, while angiotensin and dopamine are counterregulatory factors in the regulation of blood pressure. The effect of SNX1 on ATR is not known. We hypothesized that SNX1, through arterial ATR sorting and trafficking, is involved in blood pressure regulation. CRISPR/Cas9 system-generated SNX1 mice showed dramatic elevations in blood pressure compared to their wild-type littermates. The angiotensin II-mediated contractile reactivity of the mesenteric arteries and ATR expression in the aortas were also increased. Moreover, immunofluorescence and immunoprecipitation analyses revealed that SNX1 and ATR were colocalized and interacted in the aortas of wild-type mice. In vitro studies revealed that ATR protein levels and downstream calcium signaling were upregulated in A10 cells treated with SNX1 siRNA. This may have resulted from decreased ATR protein degradation since the ATR mRNA levels showed no changes. ATR protein was less degraded when SNX1 was downregulated, as reflected by a cycloheximide chase assay. Furthermore, proteasomal rather than lysosomal inhibition increased ATR protein content, and this effect was accompanied by decayed binding of ubiquitin and ATR after SNX1 knockdown. Confocal microscopy revealed that ATR colocalized with PSMD6, a proteasomal marker, and the colocalization was reduced after SNX1 knockdown. These findings suggest that SNX1 sorts ATR for proteasomal degradation and that SNX1 impairment increases arterial ATR expression, leading to increased vasoconstriction and blood pressure.