Determinants of the differential gating properties of Cav3.1 and Cav3.3 T-type channels: a role of domain IV?
We have investigated the channel structural determinants that underlie the difference in gating properties of Cav3.1 and Cav3.3 T-type channels, by creating a series of chimeric channel constructs in which the major transmembrane domains were swapped. The chimeras were then expressed in tsA-201 cells and subjected to whole cell patch clamp analysis. Our data reveal that domains I and IV are major determinants of the half-activation potential. Substitution of domain IV was the most important determinant of activation time constant and time constant for recovery from inactivation, with domains I and II mediating a smaller role. In contrast, the carboxy terminal region did not appear to be involved. Determinants of the time constant for inactivation could not be localized to a specific transmembrane domain, but the concomitant substitution of domains I+IV was able to partially confer the inactivation kinetics among the two wild type channels. Our data indicate that the domain IV region mediates an important role in T-type channel activation, whereas multiple channel structural determinants appear to control T-type channel inactivation.
Hamid
J
J
Hotchkiss Brain Institute and Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive Northwest, Calgary, Canada T2N 4N1.
Peloquin
J B
JB
Monteil
A
A
Zamponi
G W
GW
D020747:Calcium Channels, T-Type / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology* / Q000528:radiation effects; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D026901:Membrane Transport Proteins / Q000235:genetics / Q000502:physiology*; D016296:Mutagenesis / Q000502:physiology; D050506:Mutant Chimeric Proteins / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D017434:Protein Structure, Tertiary / Q000502:physiology; D014162:Transfection / Q000379:methods
C121855:CACNA1G protein, human; C469757:CACNA1I protein, human; D020747:Calcium Channels, T-Type; D026901:Membrane Transport Proteins; D050506:Mutant Chimeric Proteins