Mechanically evoked 5-hydroxytryptamine release is mediated by caveolin-associated cholesterol rich membrane domains.

5-Hydroxytryptamine (5-HT) from enterochromaffin cells activates neural reflexes that govern intestinal motility and secretion. Mechanical stimulation of human enterochromaffin cell-derived BON cells activates a G alpha q-signalling pathway coupled to 5-HT release. Molecular mechanisms identifying elements of mechanosensory transduction are unknown. The aim of this study was to determine the role of caveolin and caveolin-associated cholesterol rich microdomains in mechanically stimulated 5-HT release from BON cells. Caveolin-1 transcripts and immunofluorescence were found in BON cells. In the static state, caveolins-1 and -2 co-precipitated with G alpha q in cholesterol rich cell fractions, but not with G alpha s, G alpha i/o and G beta. Mechanical stimulation transiently uncoupled G alpha q from caveolin-1 and increased 5-HT release. Disassembly of caveolin-associated membrane microdomains by filipin or by cholesterol depletion with methyl-beta-cyclodextrin decreased mechanically evoked 5-HT release. These results suggest that caveolin and caveolin-associated cholesterol rich membrane microdomains are key regulators in mechanically evoked 5-HT release from enterochromaffin cells.