Severe Arterial Hypertension from Cullin 3 Mutations Is Caused by Both Renal and Vascular Effects.

Abstract

Mutations in four genes, WNK lysine deficient protein kinase 1 and 4 (<i>WNK1</i> and <i>WNK4</i>), kelch like family member 3 (<i>KLHL3</i>), or Cullin 3 (<i>CUL3</i>), can result in familial hyperkalemic hypertension (FHHt), a rare Mendelian form of human arterial hypertension. Although all mutations result in an increased abundance of WNK1 or WNK4, all FHHt-causing <i>CUL3</i> mutations, resulting in the skipping of exon 9, lead to a more severe phenotype. We created and compared two mouse models, one expressing the mutant Cul3 protein ubiquitously (<i>pgk-Cul3∆9</i>) and the other specifically in vascular smooth muscle cells (<i>SM22-Cul3∆9</i>). We conducted pharmacologic investigations on isolated aortas and generated stable and inducible HEK293 cell lines that overexpress the wild-type Cul3 or mutant Cul3 (Cul3<i>∆</i>9) protein. As expected, <i>pgk-Cul3∆9</i> mice showed marked hypertension with significant hyperkalemia, hyperchloremia and low renin. BP increased significantly in <i>SM22-Cul3∆9</i> mice, independent of any measurable effect on renal transport. Only <i>pgk-Cul3∆9</i> mice displayed increased expression of the sodium chloride cotransporter and phosphorylation by the WNK-SPAK kinases. Both models showed altered reactivity of isolated aortas to phenylephrine and acetylcholine, as well as marked acute BP sensitivity to the calcium channel blocker amlodipine. Aortas from <i>SM22-Cul3∆9</i> mice showed increased expression of RhoA, a key molecule involved in regulation of vascular tone, compared with aortas from control mice. We also observed increased RhoA abundance and <i>t</i>_1/2 in Cul3<i>∆</i>9-expressing cells, caused by decreased ubiquitination. Mutations in <i>Cul3</i> cause severe hypertension by affecting both renal and vascular function, the latter being associated with activation of RhoA.