A molecular determinant of nickel inhibition in Cav3.2 T-type calcium channels.
Molecular cloning studies have revealed that heterogeneity of T-type Ca2+ currents in native tissues arises from the three isoforms of Ca(v)3 channels: Ca(v)3.1, Ca(v)3.2, and Ca(v)3.3. From pharmacological analysis of the recombinant T-type channels, low concentrations (<50 microM) of nickel were found to selectively block the Ca(v)3.2 over the other isoforms. To date, however, the structural element(s) responsible for the nickel block on the Ca(v)3.2 T-type Ca2+ channel remain unknown. Thus, we constructed chimeric channels between the nickel-sensitive Ca(v)3.2 and the nickel-insensitive Ca(v)3.1 to localize the region interacting with nickel. Systematic assaying of serial chimeras suggests that the region preceding domain I S4 of Ca(v)3.2 contributes to nickel block. Point mutations of potential nickel-interacting sites revealed that H191Q in the S3-S4 loop of domain I significantly attenuated the nickel block of Ca(v)3.2, mimicking the nickel-insensitive blocking potency of Ca(v)3.1. These findings indicate that His-191 in the S3-S4 loop is a critical residue conferring nickel block to Ca(v)3.2 and reveal a novel role for the S3-S4 loop to control ion permeation through T-type Ca2+ channels.
Kang
Ho-Won
HW
Department of Life Science, Interdisciplinary Program of Biotechnology, Sogang University, Shinsu-dong, Seoul 121-742, Korea.
Park
Jin-Yong
JY
Jeong
Seong-Woo
SW
Kim
Jin-Ah
JA
Moon
Hyung-Jo
HJ
Perez-Reyes
Edward
E
Lee
Jung-Ha
JH
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D020747:Calcium Channels, T-Type / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D003001:Cloning, Molecular; D004594:Electrophysiology; D006639:Histidine / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D007477:Ions; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009532:Nickel / Q000737:chemistry / Q000494:pharmacology*; D009865:Oocytes / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D018075:RNA, Complementary / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
C121855:CACNA1G protein, human; C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type; D007477:Ions; D020033:Protein Isoforms; D018075:RNA, Complementary; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D006639:Histidine; D009532:Nickel