The cytosolic II-III loop of Cav2.3 provides an essential determinant for the phorbol ester-mediated stimulation of E-type Ca2+ channel activity.
There is growing evidence that E-type voltage dependent Ca(2+) channels (Ca(v)2.3) are involved in triggering and controlling pivotal cellular processes like neurosecretion and long-term potentiation. The mechanism underlying a novel Ca(2+) dependent stimulation of E-type Ca(2+) channels was investigated in the context of the recent finding that influx of Ca(2+) through other voltage dependent Ca(2+) channels is necessary and sufficient to directly activate protein kinase C (PKC). With Ba(2+) as charge carrier through Ca(v)2.3 channel alpha(1) subunits expressed in HEK-293 cells, activation of PKC by low concentrations of phorbol ester augmented peak I(Ba) by approximately 60%. In addition, the non-inactivating fraction of I(Ba) was increased by more than three-fold and recovery from short-term inactivation was accelerated. The effect of phorbol ester on I(Ba) was inhibited by application of the specific PKC inhibitor bisindolylmaleimide I. With Ca(2+) as charge carrier, application of phorbol ester did not change the activity of Ca(v)2.3 currents but they were modified by the PKC inhibitor bisindolylmaleimide I. These results suggest that with Ca(2+) as charge carrier the incoming Ca(2+) can activate PKC, thereby augmenting Ca(2+) influx into the cytosol. No modulation of Ca(v)2.3 channels by PKC was observed when an arginine rich region in the II-III loop of Ca(v)2.3 was eliminated. Receptor independent stimulation of PKC and its interaction with Ca(v)2.3 channels therefore represents an important positive feedback mechanism to decode electrical signals into a variety of cellular functions.
Klöckner
Udo
U
Institute of Vegetative Physiology, University of Cologne, Germany. udo.kloeckner@medizin.uni-halle.de
Pereverzev
Alexey
A
Leroy
Jérôme
J
Krieger
Andreas
A
Vajna
Rolf
R
Pfitzer
Gabriele
G
Hescheler
Jürgen
J
Malécot
Claire O
CO
Schneider
Toni
T
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D007668:Kidney; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010703:Phorbol Esters / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D013997:Time Factors; D014162:Transfection
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D010703:Phorbol Esters; D021122:Protein Subunits; D001464:Barium; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D002118:Calcium