Dual function of the voltage-dependent Ca2+ channel alpha 2 delta subunit in current stimulation and subunit interaction.
Voltage-dependent Ca2+ channels are modulated by complex interactions with the alpha 2 delta subunit. In vitro translation was used to demonstrate a single transmembrane topology of the alpha 2 delta subunit in which all but the transmembrane sequence and 5 carboxy-terminal amino acids are extracellular. The glycosylated extra-cellular domain is required for current stimulation, as shown by coexpression of truncated alpha 2 delta subunits with alpha 1A and beta 4 subunits in Xenopus oocytes and deglycosylation with peptide-N-glycosidase F. However, coexpression of the transmembrane domain-containing delta subunit reduced the stimulatory effects of full-length alpha 2 delta subunits and substitution of a different transmembrane domain resulted in a loss of current stimulation. These results support a model whereby the alpha 2 delta transmembrane domain mediates subunit interactions and the glycosylated extracellular domain enhances current amplitude.
Gurnett
C A
CA
Howard Hughes Medical Institute, Department of Physiology and Biophysics University of Iowa College of Medicine, Iowa City 52242, USA.
De Waard
M
M
Campbell
K P
KP
D000818:Animals; D000906:Antibodies / Q000737:chemistry; D015220:Calcium Channels / Q000737:chemistry / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005260:Female; D006031:Glycosylation; D008958:Models, Molecular; D009865:Oocytes / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010449:Peptide Mapping; D051381:Rats; D014981:Xenopus
D000906:Antibodies; D015220:Calcium Channels; D010446:Peptide Fragments