A CaV2.1 N-terminal fragment relieves the dominant-negative inhibition by an Episodic ataxia 2 mutant.
Episodic ataxia 2 (EA2) is an autosomal dominant disorder caused by mutations in the gene CACNA1A that encodes the pore-forming CaV2.1 calcium channel subunit. The majority of EA2 mutations reported so far are nonsense or deletion/insertion mutations predicted to form truncated proteins. Heterologous expression of wild-type CaV2.1, together with truncated constructs that mimic EA2 mutants, significantly suppressed wild-type calcium channel function, indicating that the truncated protein produces a dominant-negative effect (Jouvenceau et al., 2001; Page et al., 2004). A similar finding has been shown for CaV2.2 (Raghib et al., 2001). We show here that a highly conserved sequence in the cytoplasmic N-terminus is involved in this process, for both CaV2.1 and CaV2.2 channels. Additionally, we were able to interfere with the suppressive effect of an EA2 construct by mutating key N-terminal residues within it. We postulate that the N-terminus of the truncated channel plays an essential part in its interaction with the full-length CaV2.1, which prevents the correct folding of the wild-type channel. In agreement with this, we were able to disrupt the interaction between EA2 and the full length channel by co-expressing a free N-terminal peptide.
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK. Electronic address: s.dahimene@ucl.ac.uk.
Shehrazade
S
Dahimene
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Karen M
KM
Page
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Manuela
M
Nieto-Rostro
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Wendy S
WS
Pratt
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Marianna
M
D'Arco
Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK. Electronic address: a.dolphin@ucl.ac.uk.
Annette C
AC
Dolphin
D000818:Animals; D001259:Ataxia / Q000235:genetics*; D020864:Calcium Channels, N-Type / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D008564:Membrane Potentials / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D009759:Nystagmus, Pathologic / Q000235:genetics*; D018408:Patch-Clamp Techniques / Q000379:methods; D011817:Rabbits; D017207:Rats, Sprague-Dawley
D020864:Calcium Channels, N-Type
Dominant negative suppression; Episodic ataxia-2; Misfolded protein; N-terminus; P/Q-type calcium channel