Molecular mechanisms of subtype-specific inhibition of neuronal T-type calcium channels by ascorbate.
T-type Ca2+ channels (T-channels) are involved in the control of neuronal excitability and their gating can be modulated by a variety of redox agents. Ascorbate is an endogenous redox agent that can function as both an anti- and pro-oxidant. Here, we show that ascorbate selectively inhibits native Ca(v)3.2 T-channels in peripheral and central neurons, as well as recombinant Ca(v)3.2 channels heterologously expressed in human embryonic kidney 293 cells, by initiating the metal-catalyzed oxidation of a specific, metal-binding histidine residue in domain 1 of the channel. Our biophysical experiments indicate that ascorbate reduces the availability of Ca(v)3.2 channels over a wide range of membrane potentials, and inhibits Ca(v)3.2-dependent low-threshold-Ca2+ spikes as well as burst-firing in reticular thalamic neurons at physiologically relevant concentrations. This study represents the first mechanistic demonstration of ion channel modulation by ascorbate, and suggests that ascorbate may function as an endogenous modulator of neuronal excitability.
Nelson
Michael T
MT
Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
Joksovic
Pavle M
PM
Su
Peihan
P
Kang
Ho-Won
HW
Van Deusen
Amy
A
Baumgart
Joel P
JP
David
Laurence S
LS
Snutch
Terrance P
TP
Barrett
Paula Q
PQ
Lee
Jung-Ha
JH
Zorumski
Charles F
CF
Perez-Reyes
Edward
E
Todorovic
Slobodan M
SM
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000378:metabolism / Q000494:pharmacology*; D020747:Calcium Channels, T-Type / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D020134:Catalytic Domain / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006801:Humans; D020646:Intralaminar Thalamic Nuclei / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D008670:Metals / Q000737:chemistry; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009924:Organ Culture Techniques; D010084:Oxidation-Reduction; D051381:Rats
C509958:Cacna1h protein, rat; D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D008670:Metals; D006639:Histidine; D001205:Ascorbic Acid