High-fat diet induces IP3R–BKCa decoupling in mesenteric VSMCs through a JPH2-dependent mechanism

Dysfunction of BKCa channels in vascular smooth muscle cells (VSMCs) has been implicated in vascular remodeling associated with obesity-induced hypertension. However, the underlying molecular mechanisms remain unclear, which is the major focus of this study. We examined the expression of BKα (KCNMA1) and BKβ1 (KCNMB1) in mesenteric arteries from high-fat diet (HFD)–treated rats compared with rats fed a normal-fat diet (NFD) using Western blot analysis. The results showed that the expression levels of both subunits were comparable between the two groups. Our inside-out patch clamp data further indicated that the Ca 2 + sensitivity and voltage dependence of BKCa channels did not differ significantly between VSMCs isolated from HFD- and NFD-treated rats. Next, we investigated the molecular coupling between BKCa channels and inositol trisphosphate receptors (IP3Rs), ligand-gated Ca 2 + channels on the sarcoplasmic reticulum (SR), using whole-cell patch clamp and co-immunoprecipitation approaches. Administration of adenophostin A (AdA), an IP3R agonist, significantly increased BKCa currents in VSMCs from both HFD- and NFD-treated rats, indicating functional IP3R–BKCa coupling. However, the AdA-induced enhancement of BKCa currents was markedly greater in VSMCs from HFD-treated rats than in those from NFD-treated rats. Co-immunoprecipitation confirmed the molecular interaction between IP3R and BKCa channels in mesenteric arteries. Total IP3R protein levels in the input (non-immunoprecipitated) samples were similar between groups; however, immunoprecipitates obtained with BKα antibodies from HFD-treated rats contained less IP3R protein than those from NFD-treated rats, suggesting weakened IP3R–BKCa coupling under HFD conditions. Interestingly, silencing junctophilin-2 (JPH2) using viral vector–mediated shRNA significantly attenuated AdA-induced increases in BKCa currents in VSMCs, whereas scrambled shRNA had no significant effect. In subsequent in vivo experiments, the BKCa channel opener NS1619 was used to functionally bypass the deficient IP3R–BKCa coupling in HFD-treated rats. Chronic treatment with NS1619 significantly ameliorated vascular remodeling in HFD-treated rats compared with untreated controls. In conclusion, our results demonstrate that the Ca 2 + sensitivity, voltage dependence, and protein expression of BKCa channels in VSMCs are comparable between HFD- and NFD-treated rats. However, IP3R–BKCa coupling is impaired in VSMCs from HFD-treated rats. Dysfunction of JPH2, the tethering protein that structurally links the sarcoplasmic reticulum to the plasma membrane, may contribute to this IP3R–BKCa decoupling, ultimately leading to the vascular hypertrophy and remodeling observed in obesity-associated hypertension. 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.