The Cdc42 inhibitor secramine B prevents cAMP-induced K+ conductance in intestinal epithelial cells.
Cyclic AMP- (cAMP) and calcium-dependent agonists stimulate chloride secretion through the coordinated activation of distinct apical and basolateral membrane channels and ion transporters in mucosal epithelial cells. Defects in the regulation of Cl- transport across mucosal surfaces occur with cystic fibrosis and V. cholerae infection and can be life threatening. Here we report that secramine B, a small molecule that inhibits activation of the Rho GTPase Cdc42, reduced cAMP-stimulated chloride secretion in the human intestinal cell line T84. Secramine B interfered with a cAMP-gated and Ba2+-sensitive K+ channel, presumably KCNQ1/KCNE3. This channel is required to maintain the membrane potential that sustains chloride secretion. In contrast, secramine B did not affect the Ca2+-mediated chloride secretion pathway, which requires a separate K+ channel activity from that of cAMP. Pirl1, another small molecule structurally unrelated to secramine B that also inhibits Cdc42 activation in vitro, similarly inhibited cAMP-dependent but not Ca2+-dependent chloride secretion. These results suggest that Rho GTPases may be involved in the regulation of the chloride secretory response and identify secramine B an inhibitor of cAMP-dependent K+ conductance in intestinal epithelial cells.
Pelish
Henry E
HE
Department of Cell Biology and the CBR Institute for Biomedical Research, Harvard Medical School, Boston, Massachusetts, USA.
Ciesla
William
W
Tanaka
Nori
N
Reddy
Krishna
K
Shair
Matthew D
MD
Kirchhausen
Tomas
T
Lencer
Wayne I
WI