Gating of human ClC-2 chloride channels and regulation by carboxy-terminal domains.
Eukaryotic ClC channels are dimeric proteins with each subunit forming an individual protopore. Single protopores are gated by a fast gate, whereas the slow gate is assumed to control both protopores through a cooperative movement of the two carboxy-terminal domains. We here study the role of the carboxy-terminal domain in modulating fast and slow gating of human ClC-2 channels, a ubiquitously expressed ClC-type chloride channel involved in transepithelial solute transport and in neuronal chloride homeostasis. Partial truncation of the carboxy-terminus abolishes function of ClC-2 by locking the channel in a closed position. However, unlike other isoforms, its complete removal preserves function of ClC-2. ClC-2 channels without the carboxy-terminus exhibit fast and slow gates that activate and deactivate significantly faster than in WT channels. In contrast to the prevalent view, a single carboxy-terminus suffices for normal slow gating, whereas both domains regulate fast gating of individual protopores. Our findings demonstrate that the carboxy-terminus is not strictly required for slow gating and that the cooperative gating resides in other regions of the channel protein. ClC-2 is expressed in neurons and believed to open at negative potentials and increased internal chloride concentrations after intense synaptic activity. We propose that the function of the ClC-2 carboxy-terminus is to slow down the time course of channel activation in order to stabilize neuronal excitability.
Garcia-Olivares
Jennie
J
Institut für Neurophysiologie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
Alekov
Alexi
A
Boroumand
Mohammad Reza
MR
Begemann
Birgit
B
Hidalgo
Patricia
P
Fahlke
Christoph
C
D001665:Binding Sites; D000090007:CLC-2 Chloride Channels; D002460:Cell Line; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003541:Cystathionine beta-Synthase / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D008954:Models, Biological; D016296:Mutagenesis; D009474:Neurons / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D011993:Recombinant Fusion Proteins; D003541:Cystathionine beta-Synthase
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