title: Stimulatory and inhibitory effects of PKC isozymes are mediated by serine/threonine PKC sites of the Cav2.3α1subunits.
abstract: Protein kinase C (PKC) isozymes modulate voltage-gated calcium (Cav) currents through Cav2.2 and Cav2.3 channels by targeting serine/threonine (Ser/Thr) phosphorylation sites of Cavα1subunits. Stimulatory (Thr-422, Ser-2108 and Ser-2132) and inhibitory (Ser-425) sites were identified in the Cav2.2α1subunits to PKCs βII and ε. In the current study, we investigated if the homologous sites of Cav2.3α1subunits (stimulatory: Thr-365, Ser-1995 and Ser-2011; inhibitory: Ser-369) behaved in similar manner. Several Ala and Asp mutants were constructed in Cav2.3α1subunits in such a way that the Ser/Thr sites can be examined in isolation. These mutants or WT Cav2.3α1along with auxiliary β1band α2/δ subunits were expressed in Xenopus oocytes and the effects of PKCs βII and ε studied on the barium current (IBa). Among these sites, stimulatory Thr-365 and Ser-1995 and inhibitory Ser-369 behaved similar to their homologs in Cav2.2α1subunits. Furthermore PKCs produced neither stimulation nor inhibition when stimulatory Thr-365 or Ser-1995 and inhibitory Ser-369 were present together. However, the PKCs potentiated the IBawhen two stimulatory sites, Thr-365 and Ser-1995 were present together, thus overcoming the inhibitory effect of Ser-369. Taken together net PKC effect may be the difference between the responses of the stimulatory and inhibitory sites.
authors.affiliation: Department of Biology, Norfolk State University, Norfolk, VA 23504, USA.
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Rajagopal
authors.affiliation: Department of Biology, Norfolk State University, Norfolk, VA 23504, USA.
authors.forename: Brittney K
authors.initials: BK
authors.lastname: Burton
authors.affiliation: Department of Biology, Norfolk State University, Norfolk, VA 23504, USA.
authors.forename: Blanche L
authors.initials: BL
authors.lastname: Fields
authors.affiliation: Department of Biology, Norfolk State University, Norfolk, VA 23504, USA.
authors.forename: India O
authors.initials: IO
authors.lastname: El
authors.affiliation: Department of Biology, Norfolk State University, Norfolk, VA 23504, USA. Electronic address: glkamatchi@nsu.edu.
authors.forename: Ganesan L
authors.initials: GL
authors.lastname: Kamatchi
mesh_terms: D000818:Animals; D001665:Binding Sites; D020864:Calcium Channels, N-Type / Q000737:chemistry* / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000502:physiology*; D011485:Protein Binding; D011493:Protein Kinase C / Q000737:chemistry* / Q000378:metabolism*; D021122:Protein Subunits; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D020864:Calcium Channels, N-Type; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011493:Protein Kinase C; D021122:Protein Subunits; D012694:Serine; D013912:Threonine
keywords: Barium current; Ca(v) channels; Isozymes; Protein interaction; Regulation; Xenopus oocytes