Transmembrane 163 (TMEM163) protein effluxes zinc

Abstract

Recent investigations of rodent Tmem163 suggest that it binds to and transports zinc as a dimer, and that alanine mutagenesis of its two speciesconserved aspartate (D123A/D127A) residues perturbs its function. Direct corroboration, however, is lacking whether it is an influx or efflux transporter in cells. We hypothesized that human TMEM163 is a zinc effluxer based on its predicted protein characteristics. We used cultured human cell lines that either stably or transiently expressed TMEM163 and pre-loaded the cells with zinc to determine transport activity. We found that TMEM163-expressing cells exhibited significant reduction of intracellular zinc levels as evidenced by two zinc-specific fluorescent dyes and radionuclide zinc-65. The specificity of the fluorescence signal was confirmed upon treatment with TPEN, a high-affinity zinc chelator. Radionuclide zinc-65 assay revealed that the efflux activity of TMEM163 has an apparent Km value of 8 micromolars. To further characterize the efflux function of

Natural Killer cells demonstrate distinct eQTL and transcriptome-wide disease associations, highlighting their role in autoimmunity

“…We also identified NK cell expression of TMEM163 as a determinant of primary biliary cirrhosis. TMEM163 encodes a transmembrane zinc transporter [57], which is hypothesised to mediate zinc accumulation into lysosomes [58]. Notably, zinc deficiency has been reported to be associated with reduced NK cell cytolytic activity [59].…”

Zinc: Multidimensional Effects on Living Organisms

“…Over the course of time, other members of the ZnT effluxers (ZnT4-ZnT10) and ZIP influxers (ZIP1-ZIP14) were identified through sequence similarity analyses, cloning, and functional experimentations [232,247]. More recently, transmembrane 163 protein (TMEM163; also known as SV31) [248,249] was functionally characterized as a dimeric protein that effluxes zinc [250] and one of us (MPC) proposed the TMEM163 be now classified as ZnT11 as a new member of the ZnT efflux family of proteins [250]. One commonality among ZIPs and ZnTs is that Histidine (H) and/or Aspartic acid (D) residues such as the HXXXD motif (where X is a non-polar amino acid) typically located within transmembrane domain (TMD)-4 and TMD5…”

Systematic in silico discovery of novel solute carrier-like proteins from proteomes

“…Given the marginal similarity to the "Cation_efflux" domain, it is tempting to assume that SLC30 proteins and TMEM163 are distantly related. Indeed, TMEM163 has been shown to bind [37] and transport Zn 2+ [38][39][40], and substitution of its proposed substratebinding residues with alanine abolished Zn 2+ efflux activity [40]. Transport has been demonstrated to be H + -coupled, and the protein functioning as a dimer [38], while extruding Zn 2+ from the cell [40].…”

“…Indeed, TMEM163 has been shown to bind [37] and transport Zn 2+ [38][39][40], and substitution of its proposed substratebinding residues with alanine abolished Zn 2+ efflux activity [40]. Transport has been demonstrated to be H + -coupled, and the protein functioning as a dimer [38], while extruding Zn 2+ from the cell [40]. Intracellularly, TMEM163 was originally shown to be expressed in synaptic vesicles [41].…”