Inhibitory Role of Ser-425 of the α1 2.2 Subunit in the Enhancement of Cav 2.2 Currents by Phorbol-12-myristate, 13-Acetate

Abstract

Voltage-gated calcium channels (Ca v ) 2.2 currents are potentiated by phorbol-12-myristate, 13-acetate (PMA), whereas Ca v 2.3 currents are increased by both PMA and acetyl-␤-methylcholine (MCh). MCh-selective sites were identified in the ␣ 1 2.3 subunit, whereas the identified PMA sites responded to both PMA and MCh (Kamatchi, G. L., Franke, R., Lynch, C., III, and Sando, J. J.

Protein kinase C isozyme-specific potentiation of expressed Cav 2.3 currents by acetyl-β-methylcholine and phorbol-12-myristate, 13-acetate

“…It is possible that the Ca v 2.3 channel subunits are under negative control by these PKC isozymes and hence their depletion led to the increased basal currents. It may be recalled here that Ser-425 of the Ca v α 1 2.2 subunit acts as an inhibitory PKC site (Fang et al, 2006) and its homologue, Ser-369 in the Ca v α 1 2.3 subunit appears to act in a similar fashion (unpublished observation). It is possible that these sites are partially phosphorylated by PKC βI and ε that are active under basal conditions.…”

“…In contrast, Thr-365, Ser-369 in the I-II linker and Ser-1995 andSer-2011 in the C-terminus of α 1 2.3 subunit were identified as both MCh-and PMA-selective sites (Kamatchi et al, 2004;Fang et al, 2005). In the α 1 2.2 subunit, Thr-422 and Ser-425 in the I-II linker and Ser-2108 and Ser-2132 in the C-terminus, the homologs of α 1 2.3 Thr-365, Ser-369, Ser-1995 andSer-2011, were the sites for PMA action (Fang et al, 2006). It is possible that the PKC isozymes activated by MCh and PMA target these specific Ser/Thr PKC phosphorylation sites.…”

Inhibition of protein kinase C (PKC) response of voltage-gated calcium (Cav)2.2 channels expressed in Xenopus oocytes by Cavβ subunits

“…It has been observed by others that Ca v b 2 subunits inhibited potentiation of Ca v 2.2 currents by phorbol-12-myristate, 13-acetate (PMA), an activator of PKC (Shistik et al, 1998). Based on the above reports, it is suggested that Ca v b subunits that were coexpressed with Ca v 2.2a 1 differentially affected the PKC response of these channels by interfering with the interaction between the PKCs and Ca v 2.2a 1 subunits, the target of these isozymes (Fang et al, 2006;Rajagopal et al, 2009). Hence systematically studying the role of Ca v b subunits on the interaction between the Ca v 2.2a 1 subunits and PKC isozymes was undertaken in this study.…”

“…The selected serine/threonine (Ser/Thr) were mutated to alanine (Ala) or aspartate (Asp) by primer extension using polymerase chain reaction (PCR) with pfuTurbo DNA polymerase (QuickChange XL sitedirected mutagenesis kit, Stratagene, La Jolla, CA, USA) as described before (Fang et al, 2006;Rajagopal et al, 2009Rajagopal et al, , 2011.…”

Pyrethroids and Their Effects on Ion Channels

“…N-type VGCCs in particular are heavily influenced by phosphorylation by protein kinase C (PKC). PKC phosphorylates several sites in the N-type VGCC; phosphorylation at threonine-422 (T422) is stimulatory while at serine-425 (S425) it is inhibitory [117,118]. Effects of PKC phosphorylation are dependent on subunit expression [119].…”