11β-HSD2 SUMOylation Modulates Cortisol-Induced Mineralocorticoid Receptor Nuclear Translocation Independently of Effects on Transactivation

Abstract

The enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) has an essential role in aldosterone target tissues, conferring aldosterone selectivity for the mineralocorticoid receptor (MR) by converting 11β-hydroxyglucocorticoids to inactive 11-ketosteroids. Congenital deficiency of 11β-HSD2 causes a form of salt-sensitive hypertension known as the syndrome of apparent mineralocorticoid excess. The disease phenotype, which ranges from mild to severe, correlates well with reduction in enzyme activity. Furthermore, polymorphisms in the 11β-HSD2 coding gene (HSD11B2) have been linked to high blood pressure and salt sensitivity, major cardiovascular risk factors. 11β-HSD2 expression is controlled by different factors such as cytokines, sex steroids, or vasopressin, but posttranslational modulation of its activity has not been explored. Analysis of 11β-HSD2 sequence revealed a consensus site for conjugation of small ubiquitin-related modifier (SUMO) peptide, a major posttranslational regulatory event in several cellular processes. Our results demonstrate that 11β-HSD2 is SUMOylated at lysine 266. Non-SUMOylatable mutant K266R showed slightly higher substrate affinity and decreased Vmax, but no effects on protein stability or subcellular localization. Despite mild changes in enzyme activity, mutant K266R was unable to prevent cortisol-dependent MR nuclear translocation. The same effect was achieved by coexpression of wild-type 11β-HSD2 with sentrin-specific protease 1, a protease that catalyzes SUMO deconjugation. In the presence of 11β-HSD2-K266R, increased nuclear MR localization did not correlate with increased response to cortisol or increased recruitment of transcriptional coregulators. Taken together, our data suggests that SUMOylation of 11β-HSD2 at residue K266 modulates cortisol-mediated MR nuclear translocation independently of effects on transactivation.

SUMOylation Landscape of Renal Cortical Collecting Duct Cells

“…As SUMOylation appears to play a major role in modulating gene expression, it was logical to hypothesize that SUMOylation is linked to the actions of aldosterone. Indeed, both the mineralocorticoid receptor (MR)42 and 11Beta-hydroxysteroid dehydrogenase type 243 , the enzyme that limits access of glucocorticoids to the MR, are SUMOylated. Furthermore, aldosterone plays a major role in renal inflammatory responses in diabetic kidney disease and a role of SUMOylation has been proposed20,44 .…”

Post-Translational Modification of MR Activity

“…While the effect of SUMOylation on enzymatic activity is mild, its impact on MR activation process is puzzling. In spite of being enzymatically active, non-SUMOylatable mutant 11ßHSD2-K266R was unable to prevent MR nuclear translocation when cells were treated with cortisol, unlike the wild type enzyme [58]. The same was detected when 11ßHSD2 SUMOylation is reversed by coexpression of sentrin-specific protease 1 (SENP1), a protease that catalyzes SUMO deconjugation.…”

“…The same was detected when 11ßHSD2 SUMOylation is reversed by coexpression of sentrin-specific protease 1 (SENP1), a protease that catalyzes SUMO deconjugation. However, MR translocated to the nucleus under these conditions does not increase transcriptional response to cortisol and shows diminished recruitment of co-activators [58]. Therefore, 11ßHSD2 SUMOylation drastically alters the ability of this enzyme to regulate MR subcellular localization, although the molecular mechanisms involved in this effect remain to be elucidated.…”

“…Therefore, transcriptional or post-transcriptional modulations of this enzyme potentially have a large impact on MR activity. We have recently described that 11ßHSD2 is modified by SUMOylation at residue K266 [58] (Figure 2). While the effect of SUMOylation on enzymatic activity is mild, its impact on MR activation process is puzzling.…”

Diagnostic approach to low‐renin hypertension

“…Post‐translational modifications seem to be involved in HSD11B2 modulation as well. In particular, SUMOylation at lysine 266 seems to affect both substrate affinity and cortisol‐dependent translocation of the MR into the nucleus …”