Membrane stretch-induced activation of a TRPM4-like nonselective cation channel in cerebral artery myocytes.
Stretch-activated cation channels (SACs) have been observed in many types of smooth muscle cells. However, the molecular identity and activation mechanisms of SACs remain poorly understood. We report that TRPM4-like cation channels are activated by membrane stretch in rat cerebral artery myocytes (CAMs). Negative pressure (> or =20 mmHg, cell-attached mode) activated single channels (approximately 20 pS) in isolated CAMs. These channels were permeable to Na(+) and Cs(+) and inhibited by Gd(3+) (30 microM) and DIDS (100 microM). The effect of negative pressure was abolished by membrane excision, but subsequent application of Ca(2+) (>100 nM) to the intracellular side of the membrane restored single channel activity that was indistinguishable from SACs. Caffeine (5 mM), which depletes SR Ca(2+)-stores, first activated and then abolished SACs. Tetracaine (100 microM), a ryanodine receptor antagonist, inhibited SACs. Overexpression of hTRPM4B in HEK293 cells resulted in the appearance of cation channels that were activated by both negative pressure and Ca(2+) and which had very similar biophysical and pharmacological properties as compared with SACs in CAMs. These studies indicate that TRPM4-like channels in CAMs can be activated by membrane stretch, possibly through ryanodine receptor activation, and this may contribute to the depolarization and concomitant vasoconstriction of intact cerebral arteries following mechanical stimulation.
Morita
Hiromitsu
H
Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA. hmorita@dent.kyushu-u.ac.jp
Honda
Akira
A
Inoue
Ryuji
R
Ito
Yushi
Y
Abe
Kihachiro
K
Nelson
Mark T
MT
Brayden
Joseph E
JE
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology*; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D005260:Female; D005682:Gadolinium / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D050052:TRPC Cation Channels / Q000235:genetics / Q000502:physiology; D050053:TRPM Cation Channels / Q000235:genetics / Q000502:physiology*; D050916:TRPV Cation Channels / Q000235:genetics / Q000502:physiology; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000502:physiology*
D001896:Boron Compounds; D015220:Calcium Channels; D012333:RNA, Messenger; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels; C500239:TRPM4 protein, rat; D050916:TRPV Cation Channels; D050051:Transient Receptor Potential Channels; C492145:Trpc6 protein, rat; C486577:Trpv4 protein, rat; D005682:Gadolinium; C109986:2-aminoethoxydiphenyl borate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid