The S218L familial hemiplegic migraine mutation promotes deinhibition of Ca(v)2.1 calcium channels during direct G-protein regulation.
Familial hemiplegic migraine type 1 (FHM-1) is caused by mutations in CACNA1A, the gene encoding for the Ca(v)2.1 subunit of voltage-gated calcium channels. Although various studies attempted to determine biophysical consequences of these mutations on channel activity, it remains unclear exactly how mutations can produce a FHM-1 phenotype. A lower activation threshold of mutated channels resulting in increased channel activity has been proposed. However, hyperactivity may also be caused by a reduction of the inhibitory pathway carried by G-protein-coupled-receptor activation. The aim of this study is to determine functional consequences of the FHM-1 S218L mutation on direct G-protein regulation of Ca(v)2.1 channels. In HEK 293 cells, DAMGO activation of human mu-opioid receptors induced a 55% Ba(2+) current inhibition through both wild-type and S218L mutant Ca(v)2.1 channels. In contrast, this mutation considerably accelerates the kinetic of current deinhibition following channel activation by 1.7- to 2.3-fold depending on membrane potential values. Taken together, these data suggest that the S218L mutation does not affect G-protein association onto the channel in the closed state but promotes its dissociation from the activated channel, thereby decreasing the inhibitory G-protein pathway. Similar results were obtained with the R192Q FHM-1 mutation, although of lesser amplitude, which seems in line with the less severe associated clinical phenotype in patients. Functional consequences of FHM-1 mutations appear thus as the consequence of the alteration of both intrinsic biophysical properties and of the main inhibitory G-protein pathway of Ca(v)2.1 channels. The present study furthers molecular insight in the physiopathology of FHM-1.
Weiss
Norbert
N
INSERM U836, Site Santé la Tronche, BP 170, 38042, Grenoble Cedex 9, France.
Sandoval
Alejandro
A
Felix
Ricardo
R
Van den Maagdenberg
Arn
A
De Waard
Michel
M
D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D005838:Genotype; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D008564:Membrane Potentials; D020325:Migraine with Aura / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D051381:Rats; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism; D014162:Transfection
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D017450:Receptors, Opioid, mu; C105656:CACNA1A protein, human; C486060:Cacna2d1 protein, rat; C491529:Cacnb4 protein, rat