*Review* **Role of the Ubiquitin Proteasome System in the Regulation of Blood Pressure: A Review**

### **Osamu Yamazaki, Daigoro Hirohama, Kenichi Ishizawa and Shigeru Shibata \***

Division of Nephrology, Department of Internal Medicine, Teikyo University School of Medicine, Tokyo 173-8605, Japan; osamu195-tky@umin.ac.jp (O.Y.); hirohama-tky@umin.ac.jp (D.H.); ken.ishizawa@gmail.com (K.I.)

**\*** Correspondence: shigeru.shibata@med.teikyo-u.ac.jp; Tel.: +81-3-3964-1211

Received: 10 July 2020; Accepted: 24 July 2020; Published: 28 July 2020

**Abstract:** The kidney and the vasculature play crucial roles in regulating blood pressure. The ubiquitin proteasome system (UPS), a multienzyme process mediating covalent conjugation of the 76-amino acid polypeptide ubiquitin to a substrate protein followed by proteasomal degradation, is involved in multiple cellular processes by regulating protein turnover in various tissues. Increasing evidence demonstrates the roles of UPS in blood pressure regulation. In the kidney, filtered sodium is reabsorbed through diverse sodium transporters and channels along renal tubules, and studies conducted till date have provided insights into the complex molecular network through which ubiquitin ligases modulate sodium transport in different segments. Components of these pathways include ubiquitin ligase neuronal precursor cell-expressed developmentally downregulated 4-2, Cullin-3, and Kelch-like 3. Moreover, accumulating data indicate the roles of UPS in blood vessels, where it modulates nitric oxide bioavailability and vasoconstriction. Cullin-3 not only regulates renal salt reabsorption but also controls vascular tone using different adaptor proteins that target distinct substrates in vascular smooth muscle cells. In endothelial cells, UPS can also contribute to blood pressure regulation by modulating endothelial nitric oxide synthase. In this review, we summarize current knowledge regarding the role of UPS in blood pressure regulation, focusing on renal sodium reabsorption and vascular function.

**Keywords:** blood pressure; renal salt reabsorption; vascular function; ubiquitin proteasome system
