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

作者：Yajima T^*; Inoue R; Yajima M; Tsuruta T; Karaki S; Hira T; Kuwahara A

来源：Acta Physiologica, 2011, 203(3): 381-389.

DOI：10.1111/j.1748-1716.2011.02331.x

• GPR 43
• G alpha(q/11)
• lipid lafts
• mucosa-submucosa preparation
• propionate
• short-circuit current

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-beta-cyclodextrin (10 mm) and mastoparan (30 mu m), 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 mu m), a G alpha(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-beta-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 G alpha(q/11), but not GPR43. Uncoupling of G alpha(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 G alpha(q/11).

• 出版日期2011-11