title: Inducible knockout mutagenesis reveals compensatory mechanisms elicited by constitutive BK channel deficiency in overactive murine bladder.
abstract: The large-conductance, voltage-dependent and Ca(2+)-dependent K(+) (BK) channel links membrane depolarization and local increases in cytosolic free Ca(2+) to hyperpolarizing K(+) outward currents, thereby controlling smooth muscle contractility. Constitutive deletion of the BK channel in mice (BK(-/-)) leads to an overactive bladder associated with increased intravesical pressure and frequent micturition, which has been revealed to be a result of detrusor muscle hyperexcitability. Interestingly, time-dependent and smooth muscle-specific deletion of the BK channel (SM-BK(-/-)) caused a more severe phenotype than displayed by constitutive BK(-/-) mice, suggesting that compensatory pathways are active in the latter. In detrusor muscle of BK(-/-) but not SM-BK(-/-) mice, we found reduced L-type Ca(2+) current density and increased expression of cAMP kinase (protein kinase A; PKA), as compared with control mice. Increased expression of PKA in BK(-/-) mice was accompanied by enhanced beta-adrenoceptor/cAMP-mediated suppression of contractions by isoproterenol. This effect was attenuated by about 60-70% in SM-BK(-/-) mice. However, the Rp isomer of adenosine-3',5'-cyclic monophosphorothioate, a blocker of PKA, only partially inhibited enhanced cAMP signaling in BK(-/-) detrusor muscle, suggesting the existence of additional compensatory pathways. To this end, proteome analysis of BK(-/-) urinary bladder tissue was performed, and revealed additional compensatory regulated proteins. Thus, constitutive and inducible deletion of BK channel activity unmasks compensatory mechanisms that are relevant for urinary bladder relaxation.
authors.affiliation: Pharmakologie und Toxikologie, Institut für Pharmazie, Universität Tübingen, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Sprossmann
authors.forename: Patrick
authors.initials: P
authors.lastname: Pankert
authors.forename: Ulrike
authors.initials: U
authors.lastname: Sausbier
authors.forename: Angela
authors.initials: A
authors.lastname: Wirth
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Zhou
authors.forename: Johannes
authors.initials: J
authors.lastname: Madlung
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Iancu
authors.initials: I
authors.lastname: Bucurenciu
authors.forename: Andreas
authors.initials: A
authors.lastname: Jakob
authors.forename: Tobias
authors.initials: T
authors.lastname: Lamkemeyer
authors.forename: Winfried
authors.initials: W
authors.lastname: Neuhuber
authors.forename: Stefan
authors.initials: S
authors.lastname: Offermanns
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shipston
authors.forename: Michael
authors.initials: M
authors.lastname: Korth
authors.forename: Alfred
authors.initials: A
authors.lastname: Nordheim
authors.forename: Peter
authors.initials: P
authors.lastname: Ruth
authors.forename: Matthias
authors.initials: M
authors.lastname: Sausbier
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction; D016296:Mutagenesis; D040901:Proteomics; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D001743:Urinary Bladder / Q000378:metabolism / Q000503:physiopathology; D053201:Urinary Bladder, Overactive / Q000235:genetics*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D000242:Cyclic AMP