TREK-1 regulation by nitric oxide and cGMP-dependent protein kinase - An essential role in smooth muscle inhibitory neurotransmission

Potassium channels activated by membrane stretch may contribute to maintenance of relaxation of smooth muscle cells in visceral hollow organs. Previous work has identified K+ channels in murine colon that are activated by stretch and further regulated by NO-dependent mechanisms. We have screened murine gastrointestinal, vascular, bladder, and uterine smooth muscles for the expression of TREK and TRAAK mRNA. Although TREK-1 was expressed in many of these smooth muscles, TREK-2 was expressed only in murine antrum and pulmonary artery. TRAAK was not expressed in any smooth muscle cells tested. Whole cell currents from TREK-1 expressed in mammalian COS cells were activated by stretch, and single channel re cordings showed that the stretch-dependent conductance was due to 90 pS channels. Sodium nitroprusside (10(-6) or 10(-5) M) and 8-Br-cGMP (10(-4) or 10(-3) M) increased TREK-1 currents in perforated whole cell and single channel recordings. Mutation of the PKG consensus sequence at serine 351 blocked the stimulatory effects of sodium nitroprusside and 8-Br-cGMP on open probability without affecting the inhibitory effects of 8-Br-cAMP. TREK-1 encodes a component of the stretch-activated K+ conductance in smooth muscles and may contribute to nitrergic inhibition of gastrointestinal muscles.