Mechanosensitivity of STREX-lacking BKCa channels in the colonic smooth muscle of the mouse.
Stretch sensitivity of Ca²(+)-activated large-conductance K(+) channels (BK(Ca)) has been observed in a variety of cell types and considered to be a potential mechanism in mechanoelectric transduction (MET). Mechanical stress is a major stimulator for the smooth muscle in the gastrointestinal (GI) tract. However, much about the role and mechanism of MET in GI smooth muscles remains unknown. The BK(Ca) shows a functional diversity due to intensive Slo I alternative splicing and different α/β-subunit assembly in various cells. The stress-regulated exon (STREX) insert is suggested to be an indispensable domain for the mechanosensitivity of BK(Ca). The purpose of this study was to determine whether the BK(Ca) in colonic myocytes of the adult mouse is sensitive to mechanical stimulation and whether the STREX insert is a crucial segment for the BK(Ca) mechanosensitivity. The α- and β1-subunit mRNAs and the α-subunit protein of the BK(Ca) channels were detected in the colonic muscularis. We found that the BK(Ca) STREX-lacking variant was abundantly expressed in the smooth muscle, whereas the STREX variant was not detectable. We demonstrated that the STREX-lacking BK(Ca) channels were also sensitive to membrane stretch. We suggest that in addition to the STREX domain, there are other additional structures in the channel responsible for mechanically coupling with the cell membrane.
Wang
Wei
W
Dept. of Physiology, Capital Medical Univ., Beijing, PR China.
Huang
Haixia
H
Hou
Dongyan
D
Liu
Ping
P
Wei
Hua
H
Fu
Xiaosuo
X
Niu
Weizhen
W
D000200:Action Potentials; D000818:Animals; D041702:BALB 3T3 Cells; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D003106:Colon / Q000033:anatomy & histology* / Q000502:physiology; D005091:Exons; D005260:Female; D014644:Genetic Variation; D015640:Ion Channel Gating / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008297:Male; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D021122:Protein Subunits; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D051036:Large-Conductance Calcium-Activated Potassium Channels; D020033:Protein Isoforms; D021122:Protein Subunits; D012333:RNA, Messenger; D002118:Calcium