Inducible knockout mutagenesis reveals compensatory mechanisms elicited by constitutive BK channel deficiency in overactive murine bladder.
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.
Sprossmann
Franz
F
Pharmakologie und Toxikologie, Institut für Pharmazie, Universität Tübingen, Germany.
Pankert
Patrick
P
Sausbier
Ulrike
U
Wirth
Angela
A
Zhou
Xiao-Bo
XB
Madlung
Johannes
J
Zhao
Hong
H
Bucurenciu
Iancu
I
Jakob
Andreas
A
Lamkemeyer
Tobias
T
Neuhuber
Winfried
W
Offermanns
Stefan
S
Shipston
Michael J
MJ
Korth
Michael
M
Nordheim
Alfred
A
Ruth
Peter
P
Sausbier
Matthias
M
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*
D051036:Large-Conductance Calcium-Activated Potassium Channels; D000242:Cyclic AMP