RT Journal Article SR Electronic T1 Destabilization of Nav1.7 Sodium Channel α-Subunit mRNA by Constitutive Phosphorylation of Extracellular Signal-Regulated Kinase: Negative Regulation of Steady-State Level of Cell Surface Functional Sodium Channels in Adrenal Chromaffin Cells JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1125 OP 1136 DO 10.1124/mol.63.5.1125 VO 63 IS 5 A1 Toshihiko Yanagita A1 Hideyuki Kobayashi A1 Yasuhito Uezono A1 Hiroki Yokoo A1 Takashi Sugano A1 Tomokazu Saitoh A1 Shin-Ichi Minami A1 Seiji Shiraishi A1 Akihiko Wada YR 2003 UL http://molpharm.aspetjournals.org/content/63/5/1125.abstract AB In cultured bovine adrenal chromaffin cells expressing Nav1.7 isoform of voltage-dependent Na+channels, treatment (≥6 h) with serum deprivation, PD98059, or U0126 increased cell surface [3H]saxitoxin ([3H]STX) binding by ∼58% (t1/2 = 12.5 h), with no change in the Kd value. Immunoblot analysis showed that either treatment attenuated constitutive phosphorylation of extracellular signal-regulated kinase (ERK) 1 and ERK2 but not of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase (JNK) 1 and JNK2. The increase of [3H]STX binding and the attenuated phosphorylation of ERK1 and ERK2 returned to the control nontreated levels after the addition of serum or the washout of PD98059- or U0126-treated cells. Simultaneous treatment of serum deprivation with PD98059 or U0126 did not produce an additional increasing effect on [3H]STX binding, compared with either treatment alone. In cells subjected to either treatment, veratridine-induced maximum 22Na+ influx was augmented by ∼47%, with no change in the EC50 value;Ptychodiscus brevis toxin-3 enhanced veratridine-induced22Na+ influx by 2-fold, as in nontreated cells. Serum deprivation, PD98059, or U0126 increased Na+ channel α- but not β1- subunit mRNA level by ∼50% between 3 and 24 h; cycloheximide, an inhibitor of protein synthesis, increased α-subunit mRNA level and nullified additional increasing effect of either treatment on α-subunit mRNA level. Either treatment prolonged half-life of α-subunit mRNA from 17.5 to ∼26.3 h without altering α-subunit gene transcription. Thus, constitutively phosphorylated/activated ERK destabilizes Na+ channel α-subunit mRNA via translational event, which negatively regulates steady-state level of α-subunit mRNA and cell surface expression of functional Na+ channels. The American Society for Pharmacology and Experimental Therapeutics