The S218L familial hemiplegic migraine mutation promotes deinhibition of Ca(v)2.1 calcium channels during direct G-protein regulation.

Norbert Weiss (1) , Alejandro Sandoval (2, 3) , Ricardo Felix (2) , Arn van den Maagdenberg (4, 5) , Michel de Waard (1)

1 GIN - Grenoble Institut des Neurosciences
2 Department of Cell Biology
3 School of Medicine FES Istacala
4 Department of Human Genetics
5 Department of Neurology

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.

Mots clés: R192Q mutation; Cav2.1 type calcium channel; Cav2.1 subunit; P/Q current; G-protein; G-protein coupled receptor; μ-opioid receptor; β-subunit.; Familial hemiplegic migraine; S218L mutation

Mots clés: β-subunit

Domaines: Biochimie, Biologie Moléculaire; Physiologie [q-bio.TO]

Norbert Weiss, Alejandro Sandoval, Ricardo Felix, Arn van den Maagdenberg, Michel de Waard. The S218L familial hemiplegic migraine mutation promotes deinhibition of Ca(v)2.1 calcium channels during direct G-protein regulation.: FHM-1 mutations promote G-protein deinhibition of Cav2.1 channels. Pflügers Archiv European Journal of Physiology, 2008, 457 (2), pp.315-26. ⟨10.1007/s00424-008-0541-2⟩. ⟨inserm-00376518⟩