title: KMUP-1 activates BKCa channels in basilar artery myocytes via cyclic nucleotide-dependent protein kinases.
abstract: This study investigated whether KMUP-1, a synthetic xanthine-based derivative, augments the delayed-rectifier potassium (K(DR))- or large-conductance Ca2+-activated potassium (BKCa) channel activity in rat basilar arteries through protein kinase-dependent and -independent mechanisms. Cerebral smooth muscle cells were enzymatically dissociated from rat basilar arteries. Conventional whole cell, perforated and inside-out patch-clamp electrophysiology was used to monitor K+- and Ca2+ channel activities. KMUP-1 (1 microM) had no effect on the K(DR) current but dramatically enhanced BKCa channel activity. This increased BKCa current activity was abolished by charybdotoxin (100 nM) and iberiotoxin (100 nM). Like KMUP-1, the membrane-permeable analogs of cGMP (8-Br-cGMP) and cAMP (8-Br-cAMP) enhanced the BKCa current. BKCa current activation by KMUP-1 was markedly inhibited by a soluble guanylate cyclase inhibitor (ODQ 10 microM), an adenylate cyclase inhibitor (SQ 22536 10 microM), competitive antagonists of cGMP and cAMP (Rp-cGMP, 100 microM and Rp-cAMP, 100 microM), and cGMP- and cAMP-dependent protein kinase inhibitors (KT5823, 300 nM and KT5720, 300 nM). Voltage-dependent L-type Ca2+ current was significantly suppressed by KMUP-1 (1 microM), and nearly abolished by a calcium channel blocker (nifedipine, 1 microM). In conclusion, KMUP-1 stimulates BKCa currents by enhancing the activity of cGMP-dependent protein kinase, and in part this is due to increasing cAMP-dependent protein kinase. Physiologically, this activation would result in the closure of voltage-dependent calcium channels and the relaxation of cerebral arteries.
authors.affiliation: Department and Graduate Institute of Pharmacology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. binnan@kmu.edu.tw
authors.forename: Bin-Nan
authors.initials: BN
authors.lastname: Wu
authors.forename: Hsiao-Fang
authors.initials: HF
authors.lastname: Tu
authors.forename: Donald G
authors.initials: DG
authors.lastname: Welsh
authors.forename: Ing-Jun
authors.initials: IJ
authors.lastname: Chen
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001488:Basilar Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D017867:Cyclic Nucleotide-Regulated Protein Kinases / Q000378:metabolism*; D051668:Delayed Rectifier Potassium Channels / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006162:Guanylate Cyclase; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D008564:Membrane Potentials / Q000187:drug effects; D032342:Muscle Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D010880:Piperidines / Q000494:pharmacology*; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D000071756:Soluble Guanylyl Cyclase; D014970:Xanthines / Q000494:pharmacology*
chemical_list: D020746:Calcium Channels, L-Type; D051668:Delayed Rectifier Potassium Channels; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D010880:Piperidines; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D018160:Receptors, Cytoplasmic and Nuclear; D014970:Xanthines; C439304:KMUP 1; D015761:4-Aminopyridine; D017867:Cyclic Nucleotide-Regulated Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase