open access

https://hdl.handle.net/2115/50370

The G-protein on cholesterol-rich membrane microdomains mediates mucosal sensing of short-chain fatty acid and secretory response in rat colon

英語

short-circuit current

2011-11

Blackwell Publishing

Acta Physiologica

203(3)

381-389

Aim: Short-chain fatty acids (SCFA) stimulate colonic contraction and secretion, which are mediated by an enteric reflex via a mucosal sensing and cholinergic mechanisms. The involvement of G-protein signal transduction was examined in the secretory response to luminal propionate sensing in rat distal colon. Methods: Mucosa-submucosa and mucosa preparations were used to measure short-circuit current (I_[sc]) and acetylcholine (ACh) release respectively. Cholesterol-rich membrane microdomains, lipid rafts/caveolae, were fractionated using a sucrose-gradient ultra-centrifugation after detergent-free extraction of the isolated colonic crypt. Results: Luminal addition of methyl-β-cyclodextrin (10 mM) and mastoparan (30 μM), lipid rafts/caveolae disruptors, significantly inhibited luminal propionate-induced (0.5 mM) increases in I_[sc], but did not affect increases in I_[sc] induced by serosal ACh (0.05 mM) or electrical field stimulation (EFS). Luminal addition of YM-254890 (10 μM), a Gα_[q/11]-selective inhibitor, markedly inhibited propionate-induced increase in I_[sc], but did not affect I_[sc] responses to ACh and EFS. Both methyl-β-cyclodextrin and YM-254890 significantly inhibited luminal propionate-induced non-neuronal release of ACh from colonocytes. Real-time PCR demonstrated that in mRNA expression of SCFA receptors, GPR 43 was far higher than that of GPR41 in the colon. Western blotting analysis revealed that the cholesterol-rich membrane microdomains that fractionated from colonic crypt cells were associated with caveolin-1, flotillin-1 and Gα_[q/11], but not GPR43. Uncoupling of Gα_[q/11] from flotillin-1 in lipid rafts occurred under desensitization of the I_[sc] response to propionate. Conclusions: These data demonstrate that the secretory response to luminal propionate in rat colon is mediated by G-protein on cholesterol-rich membrane microdomains, provably via Gα_[q/11].

学術雑誌論文

Accepted Manuscript

Author Posting. © The Authors 2011. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Acta Physiologica, 203(3), 381–389. http://dx.doi.org/10.1111/j.1748-1716.2011.02331.x

1748-1708