title: ZnT-1 enhances the activity and surface expression of T-type calcium channels through activation of Ras-ERK signaling.
abstract: Zinc transporter-1 (ZnT-1) is a putative zinc transporter that confers cellular resistance from zinc toxicity. In addition, ZnT-1 has important regulatory functions, including inhibition of L-type calcium channels and activation of Raf-1 kinase. Here we studied the effects of ZnT-1 on the expression and function of T-type calcium channels. In Xenopus oocytes expressing voltage-gated calcium channel (CaV) 3.1 or CaV3.2, ZnT-1 enhanced the low-threshold calcium currents (I(caT)) to 182 ± 15 and 167.95 ± 9.27% of control, respectively (P < 0.005 for both channels). As expected, ZnT-1 also enhanced ERK phosphorylation. Coexpression of ZnT-1 and nonactive Raf-1 blocked the ZnT-1-mediated ERK phosphorylation and abolished the ZnT-1-induced augmentation of I(caT). In mammalian cells (Chinese hamster ovary), coexpression of CaV3.1 and ZnT-1 increased the I(caT) to 166.37 ± 6.37% compared with cells expressing CaV3.1 alone (P < 0.01). Interestingly, surface expression measurements using biotinylation or total internal reflection fluorescence microscopy indicated marked ZnT-1-induced enhancement of CaV3.1 surface expression. The MEK inhibitor PD-98059 abolished the ZnT-1-induced augmentation of surface expression of CaV3.1. In cultured murine cardiomyocytes (HL-1 cells), transient exposure to zinc, leading to enhanced ZnT-1 expression, also enhanced the surface expression of endogenous CaV3.1 channels. Consistently, in these cells, endothelin-1, a potent activator of Ras-ERK signaling, enhanced the surface expression of CaV3.1 channels in a PD-98059-sensitive manner. Our findings indicate that ZnT-1 enhances the activity of CaV3.1 and CaV3.2 through activation of Ras-ERK signaling. The augmentation of CaV3.1 currents by Ras-ERK activation is associated with enhanced trafficking of the channel to the plasma membrane.
authors.affiliation: Department of Physiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Merav
authors.initials: M
authors.lastname: Mor
authors.forename: Ofer
authors.initials: O
authors.lastname: Beharier
authors.forename: Shiri
authors.initials: S
authors.lastname: Levy
authors.forename: Joy
authors.initials: J
authors.lastname: Kahn
authors.forename: Shani
authors.initials: S
authors.lastname: Dror
authors.forename: Daniel
authors.initials: D
authors.lastname: Blumenthal
authors.forename: Levi A
authors.initials: LA
authors.lastname: Gheber
authors.forename: Asher
authors.initials: A
authors.lastname: Peretz
authors.forename: Amos
authors.initials: A
authors.lastname: Katz
authors.forename: Arie
authors.initials: A
authors.lastname: Moran
authors.forename: Yoram
authors.initials: Y
authors.lastname: Etzion
mesh_terms: D000818:Animals; D016466:CHO Cells; D020747:Calcium Channels, T-Type / Q000096:biosynthesis*; D027682:Cation Transport Proteins / Q000096:biosynthesis* / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D005260:Female; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism* / Q000502:physiology; D014982:Xenopus laevis
chemical_list: C121855:CACNA1G protein, human; C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type; D027682:Cation Transport Proteins; C485803:Slc30a1 protein, mouse; D016283:Proto-Oncogene Proteins p21(ras)