Two amino acid residues in the IIIS5 segment of L-type calcium channels differentially contribute to 1,4-dihydropyridine sensitivity.
The transmembrane segment IIIS5 of the L-type calcium channel alpha1 subunit participates in the formation of the 1,4-dihydropyridine (DHP) interaction domain (Grabner, M., Wang, Z., Hering, S., Striessnig, J., and Glossmann, H. (1996) Neuron 16, 207-218). We applied mutational analysis to identify amino acid residues within this segment that contribute to DHP sensitivity. DHP agonist and antagonist modulation of Ba2+ inward currents was assessed after coexpression of chimeric and mutant calcium channel alpha1 subunits with alpha2delta and beta1a subunits in Xenopus oocytes. Whereas DHP antagonists required Thr-1066, DHP agonist modulation crucially depended on the additional presence of Gln-1070 (numbering according to alpha1C-a), which also further increased the sensitivity to DHP antagonists. Asp-955, which is found at the corresponding position in the calcium channel alpha1S subunit from carp skeletal muscle, displayed functional similarity to Gln-1070 with respect to DHP interaction. We conclude that these residues (Thr-1066 plus Gln-1070 or Asp-955), which are located in close vicinity on the same side of the putative alpha-helix of transmembrane segment IIIS5, form a crucial DHP binding motif.
Mitterdorfer
J
J
Institut für Biochemische Pharmakologie, Peter Mayr Strasse 1, A-6020 Innsbruck, Austria. biochem-pharmakologie@iubk.ac.at
Wang
Z
Z
Sinnegger
M J
MJ
Hering
S
S
Striessnig
J
J
Grabner
M
M
Glossmann
H
H
D000595:Amino Acid Sequence; D000818:Animals; D002121:Calcium Channel Blockers / Q000737:chemistry*; D015220:Calcium Channels / Q000737:chemistry*; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry; D004095:Dihydropyridines / Q000494:pharmacology*; D018969:Insulin-Like Growth Factor Binding Proteins; D015640:Ion Channel Gating; D008562:Membrane Glycoproteins / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D011817:Rabbits; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002352:Carrier Proteins; D004095:Dihydropyridines; D018969:Insulin-Like Growth Factor Binding Proteins; D008562:Membrane Glycoproteins; C102529:insulin-like growth factor binding protein-related protein 1; C038806:1,4-dihydropyridine