Molecular determinants of inactivation within the I-II linker of alpha1E (CaV2.3) calcium channels.
Voltage-dependent inactivation of CaV2.3 channels was investigated using point mutations in the beta-subunit-binding site (AID) of the I-II linker. The quintuple mutant alpha1E N381K + R384L + A385D + D388T + K389Q (NRADK-KLDTQ) inactivated like the wild-type alpha1E. In contrast, mutations of alpha1E at position R378 (position 5 of AID) into negatively charged residues Glu (E) or Asp (D) significantly slowed inactivation kinetics and shifted the voltage dependence of inactivation to more positive voltages. When co-injected with beta3, R378E inactivated with tau(inact) = 538 +/- 54 ms (n = 14) as compared with 74 +/- 4 ms (n = 21) for alpha1E (p < 0.001) with a mid-potential of inactivation E(0.5) = -44 +/- 2 mV (n = 10) for R378E as compared with E(0.5) = -64 +/- 3 mV (n = 9) for alpha1E. A series of mutations at position R378 suggest that positively charged residues could promote voltage-dependent inactivation. R378K behaved like the wild-type alpha1E whereas R378Q displayed intermediate inactivation kinetics. The reverse mutation E462R in the L-type alpha1C (CaV1.2) produced channels with inactivation properties comparable to alpha1E R378E. Hence, position 5 of the AID motif in the I-II linker could play a significant role in the inactivation of Ca(V)1.2 and CaV2.3 channels.
Berrou
L
L
Department of Physiology, Membrane Transport Research Group, Université de Montréal, Montréal, Québec H3C 3J7 Canada.
Bernatchez
G
G
Parent
L
L
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D017354:Point Mutation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D014982:Xenopus laevis
C423009:CACNA1E protein, human; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D011994:Recombinant Proteins