Differential role of the alpha1C subunit tails in regulation of the Cav1.2 channel by membrane potential, beta subunits, and Ca2+ ions.
Voltage-gated Ca(v)1.2 channels are composed of the pore-forming alpha1C and auxiliary beta and alpha2delta subunits. Voltage-dependent conformational rearrangements of the alpha1C subunit C-tail have been implicated in Ca2+ signal transduction. In contrast, the alpha1C N-tail demonstrates limited voltage-gated mobility. We have asked whether these properties are critical for the channel function. Here we report that transient anchoring of the alpha1C subunit C-tail in the plasma membrane inhibits Ca2+-dependent and slow voltage-dependent inactivation. Both alpha2delta and beta subunits remain essential for the functional channel. In contrast, if alpha1C subunits with are expressed alpha2delta but in the absence of a beta subunit, plasma membrane anchoring of the alpha1C N terminus or its deletion inhibit both voltage- and Ca2+-dependent inactivation of the current. The following findings all corroborate the importance of the alpha1C N-tail/beta interaction: (i) co-expression of beta restores inactivation properties, (ii) release of the alpha1C N terminus inhibits the beta-deficient channel, and (iii) voltage-gated mobility of the alpha1C N-tail vis a vis the plasma membrane is increased in the beta-deficient (silent) channel. Together, these data argue that both the alpha1C N- and C-tails have important but different roles in the voltage- and Ca2+-dependent inactivation, as well as beta subunit modulation of the channel. The alpha1C N-tail may have a role in the channel trafficking and is a target of the beta subunit modulation. The beta subunit facilitates voltage gating by competing with the N-tail and constraining its voltage-dependent rearrangements. Thus, cross-talk between the alpha1C C and N termini, beta subunit, and the cytoplasmic pore region confers the multifactorial regulation of Ca(v)1.2 channels.
Kobrinsky
Evgeny
E
Laboratory of Clinical Investigation, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
Tiwari
Swasti
S
Maltsev
Victor A
VA
Harry
Jo Beth
JB
Lakatta
Edward
E
Abernethy
Darrell R
DR
Soldatov
Nikolai M
NM
D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology; D031541:Fluorescence Resonance Energy Transfer; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007477:Ions; D008564:Membrane Potentials; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010641:Phenotype; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors
C079146:CACNA1C protein, human; D020746:Calcium Channels, L-Type; D007477:Ions; C419385:L-type calcium channel alpha(1C); D009419:Nerve Tissue Proteins; D010455:Peptides; D049452:Green Fluorescent Proteins; D002118:Calcium