Known calcium channel alpha1 subunits can form low threshold small conductance channels with similarities to native T-type channels.
Native T-type voltage-dependent calcium channels are low voltage-activated and have a small single channel conductance of 5-8 pS, which distinguishes them from any known cloned calcium channels whose conductances are 12-25 pS. Here, we show that when alpha1B, alpha1E, or alpha1C are expressed in COS7 cells, which contain no endogenous calcium channel subunits or calcium channels, they each exhibit a 4-7 pS channel as well as a large conductance channel. At low depolarizations, or when the alpha1 subunit is expressed in the absence of auxiliary alpha2-delta or beta subunits, the small conductance channels are seen alone, and their biophysical properties, including voltage dependence and kinetics of activation and inactivation, are very similar to native T-type calcium channels.
Meir
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Department of Pharmacology, University College London, United Kingdom.
Dolphin
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AC
D000818:Animals; D019556:COS Cells; D015220:Calcium Channels / Q000737:chemistry* / Q000235:genetics*; D004553:Electric Conductivity; D015870:Gene Expression; D005910:Glioma; D006822:Hybrid Cells / Q000737:chemistry / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma; D018408:Patch-Clamp Techniques; D051381:Rats; D014162:Transfection
D015220:Calcium Channels