title: Effects of isoflurane on the expressed Cav2.2 currents in Xenopus oocytes depend on the activation of protein kinase Cδ and its phosphorylation sites in the Cav2.2α1 subunits.
abstract: The effects of isoflurane on the modulation of two neuronal voltage-gated calcium channels (Ca(v); Ca(v)2.1 and 2.2) by protein kinase C (PKC) isozymes βII, ε or δ and their combination were examined. Ca(v)2.1α1 or Ca(v)2.2α1 with β1b and α2δ subunits were expressed in Xenopus oocytes and the currents (I(Ba)) were recorded by two-electrode voltage clamp. Isoflurane (0.70 mM) decreased both Ca(v)2.1 and 2.2 currents by 20-35% and also caused translocation of PKCδ to the membrane. Compared to the wild type (WT), isoflurane caused greater inhibition of Ca(v)2.2 currents in the absence of stimulatory PKC sites (Thr-422, Ser-1757, Ser-2108, Ser-2132) and in the presence of inhibitory PKC site (Ser-425). In contrast, isoflurane caused less inhibition of I(Ba) in the oocytes expressing S425A, the inhibitory site mutant, compared to WT. PKCδ by itself did not modulate Ca(v)2.2 currents, but potentiated these currents in the presence of isoflurane. PKCε increased Ca(v)2.2 currents either alone or in combination with isoflurane. Ca(v)2.1 currents were not modulated by phorbol-12-myristate, 13-acetate (PMA) or acetyl-β-methylcholine (MCh), activators of PKC. Yet the presence of isoflurane caused PMA (but not MCh) to enhance Ca(v)2.1 currents. PKCβII and PKCε isozymes activated by PMA, did not alter Ca(v)2.1 currents. However, in the presence of isoflurane, these two isozymes together potentiated Ca(v)2.1 currents. The variable responses of Ca(v)2.1 currents to PKCβII and PKCε and Ca(v)2.2 currents to PKCδ in the presence of isoflurane may be due to increased affinity or accessibility of these isozymes to their Ser/Thr PKC sites of Ca(v)α1 subunits.
authors.affiliation: Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: S
authors.initials: S
authors.lastname: Rajagopal
authors.forename: H
authors.initials: H
authors.lastname: Fang
authors.forename: C
authors.initials: C
authors.lastname: Lynch
authors.forename: J J
authors.initials: JJ
authors.lastname: Sando
authors.forename: G L
authors.initials: GL
authors.lastname: Kamatchi
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects* / Q000502:physiology; D005260:Female; D007530:Isoflurane / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051745:Protein Kinase C-delta / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D018685:Anesthetics, Inhalation; C527798:CACNA1B protein, Xenopus; D020864:Calcium Channels, N-Type; D021122:Protein Subunits; D029867:Xenopus Proteins; D007530:Isoflurane; D051745:Protein Kinase C-delta