Deletion of TRPC4 and TRPC6 in mice impairs smooth muscle contraction and intestinal motility in vivo.
OBJECTIVE
Downstream effects of muscarinic receptor stimulation in intestinal smooth muscle include contraction and intestinal transit. We thought to determine whether classic transient receptor potential (TRPC) channels integrate the intracellular signaling cascades evoked by the stimulated receptors and thereby contribute to the control of the membrane potential, Ca-influx, and cell responses.


METHODS
We created trpc4-, trpc6-, and trpc4/trpc6-gene-deficient mice and analyzed them for intestinal smooth muscle function in vitro and in vivo.


RESULTS
In intestinal smooth muscle cells TRPC4 forms a 55 pS cation channel and underlies more than 80% of the muscarinic receptor-induced cation current (mI(CAT)). The residual mI(CAT) depends on the expression of TRPC6, indicating that TRPC6 and TRPC4 determine mI(CAT) channel activity independent of other channel subunits. In TRPC4-deficient ileal myocytes the carbachol-induced membrane depolarizations are diminished greatly and the atropine-sensitive contraction elicited by acetylcholine release from excitatory motor neurons is reduced greatly. Additional deletion of TRPC6 aggravates these effects. Intestinal transit is slowed down in mice lacking TRPC4 and TRPC6.


CONCLUSIONS
In intestinal smooth muscle cells TRPC4 and TRPC6 channels are gated by muscarinic receptors and are responsible for mI(CAT). They couple muscarinic receptors to depolarization of intestinal smooth muscle cells and voltage-activated Ca(2+)-influx and contraction, and thereby accelerate small intestinal motility in vivo.
Tsvilovskyy
Volodymyr V
VV
Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg, Germany.
Zholos
Alexander V
AV
Aberle
Thomas
T
Philipp
Stephan E
SE
Dietrich
Alexander
A
Zhu
Michael X
MX
Birnbaumer
Lutz
L
Freichel
Marc
M
Flockerzi
Veit
V
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004558:Electric Stimulation; D017615:Enteric Nervous System / Q000378:metabolism; D005769:Gastrointestinal Motility / Q000187:drug effects; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D015640:Ion Channel Gating; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism; D050052:TRPC Cation Channels / Q000172:deficiency* / Q000235:genetics; D000074287:TRPC6 Cation Channel
D020746:Calcium Channels, L-Type; D018679:Cholinergic Agonists; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; D000074287:TRPC6 Cation Channel; C492146:Trpc6 protein, mouse; D001285:Atropine; D002217:Carbachol; D000109:Acetylcholine