Activation of protein kinase C augments T-type Ca2+ channel activity without changing channel surface density.
T-type Ca2+ channels play essential roles in numerous cellular processes. Recently, we reported that phorbol-12-myristate-13-acetate (PMA) potently enhanced the current amplitude of Cav3.2 T-type channels reconstituted in Xenopus oocytes. Here, we have compared PMA modulation of the activities of Cav3.1, Cav3.2 and Cav3.3 channels, and have investigated the underlying mechanism. PMA augmented the current amplitudes of the three T-type channel isoforms, but the fold stimulations and time courses differed. The augmentation effects were not mimicked by 4alpha-PMA, an inactive stereoisomer of PMA, but were abolished by preincubation with protein kinase C (PKC) inhibitors, indicating that PMA augmented T-type channel currents via activation of oocyte PKC. The stimulation effect on Cav3.1 channel activity by PKC was mimicked by endothelin when endothelin receptor type A was coexpressed with Cav3.1 in the Xenopus oocyte system. Pharmacological studies combined with fluorescence imaging revealed that the surface density of Cav3.1 T-type channels was not significantly changed by activation of PKC. The PKC effect on Cav3.1 was localized to the cytoplasmic II-III loop using chimeric channels with individual cytoplasmic loops of Cav3.1 replaced by those of Cav2.1.
Park
Jin-Yong
JY
Department of Life Science, Sogang University, Shinsu-dong, Seoul 121-742, Korea.
Kang
Ho-Won
HW
Moon
Hyung-Jo
HJ
Huh
Sung-Un
SU
Jeong
Seong-Woo
SW
Soldatov
Nikolai M
NM
Lee
Jung-Ha
JH
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000032:analysis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000378:metabolism; D008845:Microinjections; D009154:Mutation; D009865:Oocytes / Q000737:chemistry / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D044022:Receptor, Endothelin A / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors; D014982:Xenopus laevis
C479952:CACNA1H protein, human; C469757:CACNA1I protein, human; C500994:Cacna1g protein, rat; D020747:Calcium Channels, T-Type; D019332:Endothelin-1; D026901:Membrane Transport Proteins; D047428:Protein Kinase Inhibitors; D044022:Receptor, Endothelin A; D011993:Recombinant Fusion Proteins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium