Novel regulation mechanism of adrenal cortisol and DHEA biosynthesis via the endogen ERAD inhibitor small VCP-interacting protein

Recep Ilhan,Esra Atalay Sahar,Yalcin Erzurumlu,Petek Ballar Kirmizibayrak,Sevil Cayli,Oguz Gozen,Sinem Yilmaz,Göklem Üner

doi:10.1038/s41598-022-04821-y

Abstract

Endoplasmic reticulum-associated degradation (ERAD) is a well-characterized mechanism of protein quality control by removal of misfolded or unfolded proteins. The tight regulation of ERAD is critical for protein homeostasis as well as lipid metabolism. Although the mechanism is complex, all ERAD branches converge on p97/VCP, a key protein in the retrotranslocation step. The multifunctionality of p97/VCP relies on its multiple binding partners, one of which is the endogenous ERAD inhibitor, SVIP (small VCP-interacting protein). As SVIP is a promising target for the regulation of ERAD, we aimed to assess its novel physiological roles. We revealed that SVIP is highly expressed in the rat adrenal gland, especially in the cortex region, at a consistently high level during postnatal development, unlike the gradual increase in expression seen in developing nerves. Steroidogenic stimulators caused a decrease in SVIP mRNA expression and increase in SVIP protein degradation in human adrenocortical H295R cells. Interestingly, silencing of SVIP diminished cortisol secretion along with downregulation of steroidogenic enzymes and proteins involved in cholesterol uptake and cholesterol biosynthesis. A certain degree of SVIP overexpression mainly increased the biosynthesis of cortisol as well as DHEA by enhancing the expression of key steroidogenic proteins, whereas exaggerated overexpression led to apoptosis, phosphorylation of eIF2α, and diminished adrenal steroid hormone biosynthesis. In conclusion, SVIP is a novel regulator of adrenal cortisol and DHEA biosynthesis, suggesting that alterations in SVIP expression levels may be involved in the deregulation of steroidogenic stimulator signaling and abnormal adrenal hormone secretion.

Highlights

Abbreviations 3β-hydroxysteroid dehydrogenase (3β-HSD) 3β-Hydroxysteroid dehydrogenase AIF Apoptosis-inducing factor angiotensin II (Ang II) Angiotensin II ACTH Adrenocorticotropin CYPs P450 heme-containing monooxygenases EEA1 Early endosome antigen 1 endoplasmic reticulum-associated degradation (ERAD) Endoplasmic reticulum-associated degradation ER Endoplasmic reticulum hydroxy-3-methylglutary coenzyme A reductase (HMGR) 3-Hydroxy-3-methylglutary coenzyme A reductase IB Immunoblotting
Our results revealed that SVIP is highly expressed in the medulla spinalis and adrenal gland in addition to the previously reported cerebrum, cerebellum, and sciatic n erve[8] (Fig. 1A)
Because it was previously reported that SVIP as an ERAD inhibitor may delay the degradation of tumor suppressor p 5314, which regulates the cell cycle and acts as guardian of genome stability, we evaluated the effect of SVIP on the p53 levels in H295R cells and found that p53 levels were increased with SVIP overexpression and decreased with SVIP silencing (Fig. 8C)

Summary

Introduction

Abbreviations 3β-HSD 3β-Hydroxysteroid dehydrogenase AIF Apoptosis-inducing factor Ang II Angiotensin II ACTH Adrenocorticotropin CYPs P450 heme-containing monooxygenases EEA1 Early endosome antigen 1 ERAD Endoplasmic reticulum-associated degradation ER Endoplasmic reticulum HMGR 3-Hydroxy-3-methylglutary coenzyme A reductase IB Immunoblotting. SVIP (small p97/VCP-interacting protein) is a membrane-anchored 76-amino acid protein that binds to p97/VCP in a mutually exclusive manner of p47, Ufd1-Npl[4], and gp[784,6]. Regulation of the levels of ERAD components leads to enhanced ERAD proteolytic activity, which was found to be positively related with prostate tumorigenesis[13] This androgen-mediated downregulation of SVIP was reported to be present in the glioma cells and involved in the cell proliferation regulation of glioma cells with wild-type p5314. We report for the first time that SVIP is highly expressed in the rat adrenal gland tissue and is involved in the regulation of human adrenal cortisol and dehydroepiandrosterone (DHEA) biosynthesis. Our findings indicate a novel role for SVIP in cortisol and DHEA biosynthesis and the homeostasis of adrenal cortex cells

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