title: The familial hemiplegic migraine type 1 mutation K1336E affects direct G protein-mediated regulation of neuronal P/Q-type Ca2+ channels.
abstract: BACKGROUND
  Familial hemiplegic migraine type 1 (FHM-1) is an autosomal dominant form of migraine with aura characterized by recurrent migraine, hemiparesis and ataxia. FHM-1 has been linked to missense mutations in the CACNA1A gene encoding the pore-forming subunit of the neuronal voltage-gated P/Q-type Ca(2+) channel (CaV2.1α1).
  
  
  METHODS
  Here, we explored the effects of the FHM-1 K1336E mutation on G protein-dependent modulation of the recombinant P/Q-type channel. The mutation was introduced into the human CaV2.1α1 subunit and its functional consequences investigated after heterologous expression in HEK-293 cells using patch-clamp recordings.
  
  
  RESULTS
  Functional analysis of the K1336E mutation revealed a reduction of Ca(2+) current densities, a ∼10 mV left-shift in the current-voltage relationship, and the slowing of current inactivation kinetics. When co-expressed along with the human μ-opioid receptor, application of the agonist DAMGO inhibited whole-cell currents through both the wild-type and the mutant channels. Prepulse facilitation was also reduced by the K1336E mutation. Likewise, the kinetic analysis of the onset and decay of facilitation showed that the mutation affects the apparent dissociation and reassociation rates of the Gβγ dimer from the channel complex.
  
  
  CONCLUSIONS
  These results suggest that the extent of G-protein-mediated inhibition is significantly reduced in the K1336E mutant CaV2.1 Ca(2+) channels. This alteration would contribute to render the neuronal network hyperexcitable, possibly as a consequence of reduced presynaptic inhibition, and may help to explain some aspects of the FHM-1 pathophysiology.
authors: Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute Cinvestav-IPN, Mexico.
authors: Edgar
authors: E
authors: Garza-López
authors: Ricardo
authors: R
authors: González-Ramírez
authors: María A
authors: MA
authors: Gandini
authors: Alejandro
authors: A
authors: Sandoval
authors: Ricardo
authors: R
authors: Felix
mesh_terms: D015220:Calcium Channels / Q000235:genetics*; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000378:metabolism*; D002524:Cerebellar Ataxia / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008881:Migraine Disorders / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D014162:Transfection
chemical_list: D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D019204:GTP-Binding Proteins; C105656:CACNA1A protein, human