Differential interactions of the C terminus and the cytoplasmic I-II loop of neuronal Ca2+ channels with G-protein alpha and beta gamma subunits. I. Molecular determination.
Interactions of G-protein alpha (Galpha) and beta gamma subunits (Gbeta gamma) with N- (alpha1B) and P/Q-type (alpha1A) Ca2+ channels were investigated using the Xenopus oocyte expression system. Gi3alpha was found to inhibit both N- and P/Q-type channels by receptor agonists, whereas Gbeta1 gamma2 was responsible for prepulse facilitation of N-type channels. L-type channels (alpha1C) were not regulated by Galpha or Gbeta gamma. For N-type, prepulse facilitation mediated via Gbeta gamma was impaired when the cytoplasmic I-II loop (loop 1) was deleted or replaced with the alpha1C loop 1. Galpha-mediated inhibitions were also impaired by substitution of the alpha1C loop 1, but only when the C terminus was deleted. For P/Q-type, by contrast, deletion of the C terminus alone diminished Galpha-mediated inhibition. Moreover, a chimera of L-type with the alpha1B loop 1 gained Gbeta gamma-dependent facilitation, whereas an L-type chimera with the N- or P/Q-type C terminus gained Galpha-mediated inhibition. These findings provide evidence that loop 1 of N-type channels is a regulatory site for Gbeta gamma and the C termini of P/Q- and N-types for Galpha.
Furukawa
T
T
Department of Neurochemistry, Tokyo Institute of Psychiatry, 2-1-8 Kamikitazawa, Setagaya-ku, Tokyo 156, Japan.
Nukada
T
T
Mori
Y
Y
Wakamori
M
M
Fujita
Y
Y
Ishida
H
H
Fukuda
K
K
Kato
S
S
Yoshii
M
M
D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D014981:Xenopus
D015220:Calcium Channels; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins