title: A quartet of leucine residues in the guanylate kinase domain of CaVβ determines the plasma membrane density of the CaV2.3 channel.
abstract: Ca(V)β subunits are formed by a Src homology 3 domain and a guanylate kinase-like (GK) domain connected through a variable HOOK domain. Complete deletion of the Src homology 3 domain (75 residues) as well as deletion of the HOOK domain (47 residues) did not alter plasma membrane density of Ca(V)2.3 nor its typical activation gating. In contrast, six-residue deletions in the GK domain disrupted cell surface trafficking and functional expression of Ca(V)2.3. Mutations of residues known to carry nanomolar affinity binding in the GK domain of Ca(V)β (P175A, P179A, M195A, M196A, K198A, S295A, R302G, R307A, E339G, N340G, and A345G) did not significantly alter cell surface targeting or gating modulation of Ca(V)2.3. Nonetheless, mutations of a quartet of leucine residues (either single or multiple mutants) in the α3, α6, β10, and α9 regions of the GK domain were found to significantly impair cell surface density of Ca(V)2.3 channels. Furthermore, the normalized protein density of Ca(V)2.3 was nearly abolished with the quadruple Ca(V)β3 Leu mutant L200G/L303G/L337G/L342G. Altogether, our observations suggest that the four leucine residues in Ca(V)β3 form a hydrophobic pocket surrounding key residues in the α-interacting domain of Ca(V)2.3. This interaction appears to play an essential role in conferring Ca(V)β-induced modulation of the protein density of Ca(V)α1 subunits in Ca(V)2 channels.
authors: Département de Physiologie and the Membrane Protein Research Group, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors: Behzad
authors: B
authors: Shakeri
authors: Benoîte
authors: B
authors: Bourdin
authors: Pierre-Olivier
authors: PO
authors: Demers-Giroux
authors: Rémy
authors: R
authors: Sauvé
authors: Lucie
authors: L
authors: Parent
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D020908:Calcium Channels, R-Type / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D017433:Protein Structure, Secondary; D051381:Rats; D018909:src Homology Domains
chemical_list: C423009:CACNA1E protein, human; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D007930:Leucine