title: Uridine adenosine tetraphosphate is a novel neurogenic P2Y1 receptor activator in the gut.
abstract: Enteric purinergic motor neurotransmission, acting through P2Y1 receptors (P2Y1R), mediates inhibitory neural control of the intestines. Recent studies have shown that NAD(+) and ADP ribose better meet criteria for enteric inhibitory neurotransmitters in colon than ATP or ADP. Here we report that human and murine colon muscles also release uridine adenosine tetraphosphate (Up4A) spontaneously and upon stimulation of enteric neurons. Release of Up4A was reduced by tetrodotoxin, suggesting that at least a portion of Up4A is of neural origin. Up4A caused relaxation (human and murine colons) and hyperpolarization (murine colon) that was blocked by the P2Y1R antagonist, MRS 2500, and by apamin, an inhibitor of Ca(2+)-activated small-conductance K(+) (SK) channels. Up4A responses were greatly reduced or absent in colons of P2ry1(-/-) mice. Up4A induced P2Y1R-SK-channel-mediated hyperpolarization in isolated PDGFRα(+) cells, which are postjunctional targets for purinergic neurotransmission. Up4A caused MRS 2500-sensitive Ca(2+) transients in human 1321N1 astrocytoma cells expressing human P2Y1R. Up4A was more potent than ATP, ADP, NAD(+), or ADP ribose in colonic muscles. In murine distal colon Up4A elicited transient P2Y1R-mediated relaxation followed by a suramin-sensitive contraction. HPLC analysis of Up4A degradation suggests that exogenous Up4A first forms UMP and ATP in the human colon and UDP and ADP in the murine colon. Adenosine then is generated by extracellular catabolism of ATP and ADP. However, the relaxation and hyperpolarization responses to Up4A are not mediated by its metabolites. This study shows that Up4A is a potent native agonist for P2Y1R and SK-channel activation in human and mouse colon.
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Leonie
authors.initials: L
authors.lastname: Durnin
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Hwang
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kurahashi
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Bernard T
authors.initials: BT
authors.lastname: Drumm
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Ward
authors.affiliation: Sasse Surgical Associates, Reno, NV 89502.
authors.forename: Kent C
authors.initials: KC
authors.lastname: Sasse
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and.
authors.forename: Kenton M
authors.initials: KM
authors.lastname: Sanders
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557; and vmutafova@medicine.nevada.edu.
authors.forename: Violeta N
authors.initials: VN
authors.lastname: Mutafova-Yambolieva
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D003106:Colon / Q000294:innervation / Q000378:metabolism*; D003838:Deoxyadenine Nucleotides / Q000494:pharmacology; D015226:Dinucleoside Phosphates / Q000494:pharmacology*; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism; D058912:Purinergic P2Y Receptor Agonists / Q000494:pharmacology*; D058472:Receptors, Purinergic P2Y1 / Q000235:genetics / Q000378:metabolism*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D013498:Suramin / Q000494:pharmacology; D014530:Uridine Diphosphate / Q000494:pharmacology
chemical_list: C495475:2-iodo-N(6)-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphate; D000970:Antineoplastic Agents; D003838:Deoxyadenine Nucleotides; D015226:Dinucleoside Phosphates; D058912:Purinergic P2Y Receptor Agonists; D058472:Receptors, Purinergic P2Y1; D051640:Small-Conductance Calcium-Activated Potassium Channels; C529314:uridine adenosine tetraphosphate; D014530:Uridine Diphosphate; D013498:Suramin; D000244:Adenosine Diphosphate
keywords: P2Y1 receptor; Up4A; enteric nervous system; intestine; purinergic signaling