IRAG is essential for relaxation of receptor-triggered smooth muscle contraction by cGMP kinase.
Signalling by cGMP-dependent protein kinase type I (cGKI) relaxes various smooth muscles modulating thereby vascular tone and gastrointestinal motility. cGKI-dependent relaxation is possibly mediated by phosphorylation of the inositol 1,4,5-trisphosphate receptor I (IP(3)RI)-associated protein (IRAG), which decreases hormone-induced IP(3)-dependent Ca(2+) release. We show now that the targeted deletion of exon 12 of IRAG coding for the N-terminus of the coiled-coil domain disrupted in vivo the IRAG-IP(3)RI interaction and resulted in hypomorphic IRAG(Delta12/Delta12) mice. These mice had a dilated gastrointestinal tract and a disturbed gastrointestinal motility. Carbachol- and phenylephrine-contracted smooth muscle strips from colon and aorta, respectively, of IRAG(Delta12/Delta12) mice were not relaxed by cGMP, while cAMP-mediated relaxation was unperturbed. Norepinephrine-induced increases in [Ca(2+)](i) were not decreased by cGMP in aortic smooth muscle cells from IRAG(Delta12/Delta12) mice. In contrast, cGMP-induced relaxation of potassium-induced smooth muscle contraction was not abolished in IRAG(Delta12/Delta12) mice. We conclude that cGMP-dependent relaxation of hormone receptor-triggered smooth muscle contraction essentially depends on the interaction of cGKI-IRAG with IP(3)RI.
Institut für Pharmakologie und Toxikologie, Technische Universität München, Biedersteiner Strasse 29, 80802 München, Germany.
Angela
A
Geiselhöringer
Matthias
M
Werner
Katja
K
Sigl
Petra
P
Smital
René
R
Wörner
Linda
L
Acheo
Juliane
J
Stieber
Pascal
P
Weinmeister
Robert
R
Feil
Susanne
S
Feil
Jörg
J
Wegener
Franz
F
Hofmann
Jens
J
Schlossmann
D000818:Animals; D001011:Aorta / Q000033:anatomy & histology / Q000187:drug effects; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002522:Chlorocebus aethiops; D018679:Cholinergic Agonists / Q000494:pharmacology; D003106:Colon / Q000033:anatomy & histology / Q000187:drug effects; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005091:Exons; D005682:Gadolinium / Q000378:metabolism; D005769:Gastrointestinal Motility / Q000187:drug effects; D041981:Gastrointestinal Tract / Q000033:anatomy & histology / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D018390:Gene Targeting; D066298:In Vitro Techniques; D008565:Membrane Proteins; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism
D018679:Cholinergic Agonists; D008565:Membrane Proteins; C485785:Mrvi1 protein, mouse; D010750:Phosphoproteins; C016276:8-bromocyclic GMP; D002217:Carbachol; D005682:Gadolinium; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D002118:Calcium