Cloning and expression of a jellyfish calcium channel beta subunit reveal functional conservation of the alpha1-beta interaction.
In high voltage-activated calcium channels, the binding between the pore-forming alpha1 subunit and the modulatory beta subunit is mediated by interaction domains in each molecule that are highly conserved among most known subunits. However, the interaction domain within CyCaalpha1, an alpha1 subunit cloned from the jellyfish Cyanea capillata, matches the canonical sequence of the alpha1 interaction domain at only four of nine sites. We have now cloned a cDNA from Cyanea neuromuscular tissue that encodes a Ca2+ channel beta subunit. The subunit, named CyCabeta, shares 47-54% identity with vertebrate beta subunit isoforms, but is most highly conserved within its interaction domain. Coexpression of CyCabeta with CyCaalpha1 in Xenopus oocytes increases the amplitude of the CyCaalpha1 current and shifts its activation to more hyperpolarized potentials. These responses are mimicked by coexpression of the rat beta2a subunit, demonstrating that the alpha1 beta interaction is functionally conserved between cnidarians and mammals. CyCabeta also markedly accelerates the rate of recovery of CyCaalpha1 from inactivation, an action that is modestly duplicated by beta2a and may represent an additional mechanism by which beta subunit isoforms differentially modulate alpha1 subunits. These findings establish that limited conservation within the alpha1 interaction domain is sufficient to allow full modulation by a beta subunit, as well as altered regulation by different beta isoforms.
Jeziorski
M C
MC
The Whitney Laboratory, University of Florida, St. Augustine 32086, USA.
Greenberg
R M
RM
Anderson
P A
PA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D005260:Female; D015870:Gene Expression; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D020836:Protein Structure, Quaternary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D037401:Scyphozoa / Q000235:genetics* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D020746:Calcium Channels, L-Type; D017931:DNA Primers; D011994:Recombinant Proteins