The RNF186 E3 Ligase Destabilizes ROMK Protein

The renal outer medullary K + channel (ROMK) is essential for potassium handling along the nephron. In the thick ascending limb (TAL), ROMK recycles K + into the tubule lumen which establishes an electrochemical gradient that drives Na + reabsorption via the Na + -K + -2Cl− cotransporter (NKCC2). In the distal nephron, ROMK facilitates urinary K + excretion to maintain K + homeostasis. Previous studies indicate that ROMK protein abundance in the TAL is ~10-fold greater than the distal nephron (DCT2, CNT, CCD) despite having similar transcript levels. We hypothesized that ubiquitin-mediated proteasomal degradation in distal segments may be underpinning. Bioinformatic analysis of kidney cell-type transcriptomes identified the E3 ligase RNF186 as enriched in the distal nephron and absent in the TAL. Here, we test if RNF186 affects ROMK protein stability. Western blot analyses of ROMK inducible HEK293 cells transfected with FLAG-tagged RNF186 showed a time-dependent decrease in ROMK protein abundance, indicative of enhanced protein degradation. Immunocytochemistry revealed colocalization of ROMK and RNF186. These results suggest segment-specific regulation of ROMK protein abundance via the E3 ubiquitin ligase RNF186. Further investigation is needed to confirm a physical interaction between ROMK and RNF186, determine the ubiquitination status, and elucidate its precise physiological context. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.