Affinage

TMEM163

Transmembrane protein 163 · UniProt Q8TC26

Length
289 aa
Mass
31.5 kDa
Annotated
2026-06-10
18 papers in source corpus 13 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TMEM163 (SV31, ZNT11/SLC30A11) is a proton-coupled zinc efflux transporter of the CDF/SLC30 family that controls cellular and vesicular zinc homeostasis (PMID:31697912). Reconstitution in proteoliposomes establishes that it mediates Zn2+ transport that depends on external zinc and an internal acidic pH, with transport activity assembling on the homodimer; two conserved aspartate residues and histidine residues are required for zinc binding (PMID:27917477), and alanine substitution of these aspartates (D124A/D128A) or the E286K variant abolishes efflux in cells (PMID:31697912). Beyond homodimers, TMEM163 heterodimerizes with ZNT1, ZNT2, and ZNT3 to form functional efflux units (PMID:36204728), and it physically interacts with the TRPML1 channel to cooperatively set intracellular zinc levels (PMID:25130899). The protein distributes across synaptic vesicles, the plasma membrane, lysosomes, and early endosomes (PMID:17623043, PMID:21668449, PMID:35455965), and its sorting to lysosome-related organelles is directed by an N-terminal acidic dileucine motif that engages the BLOC-1 and AP-3 complexes through competitive, sequential binding; disruption of this motif strands the protein at the plasma membrane (PMID:41985787). Through this zinc-handling activity TMEM163 functions in diverse physiological contexts, including modulation of ATP-gated P2X receptor pharmacology and pain behavior (PMID:32492420), zinc-regulated insulin storage and secretion in pancreatic beta cells (PMID:31813547), and vesicular zinc release from dorsal root ganglion neurons that tunes spinal itch circuits (PMID:39602426). Heterozygous missense variants in its conserved cytoplasmic domain impair zinc efflux and cause hypomyelinating leukodystrophy, with mutant protein disrupting myelin gene expression and oligodendrocyte development in cells and zebrafish (PMID:35953447, PMID:35455965).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2007 High

    Established TMEM163 as a bona fide membrane protein with a defined subcellular home, anchoring all later functional work in synaptic vesicle biology.

    Evidence Subcellular fractionation, immunoelectron microscopy, and immunocytochemistry of brain identifying SV31 on synaptic vesicles of glutamatergic and GABAergic terminals

    PMID:17623043

    Open questions at the time
    • No transport activity or substrate demonstrated
    • Topology and oligomeric state unresolved
  2. 2011 High

    Defined the substrate selectivity of the protein, showing it binds Zn2+ and Ni2+ but not Ca2+/Fe2+/Mn2+, pointing toward a zinc-handling role.

    Evidence Recombinant metal-binding assays plus PC12 cell localization with FluoZin-3 and vesicle/endosome markers

    PMID:21668449

    Open questions at the time
    • Binding does not establish vectorial transport
    • Direction of zinc flux not determined
  3. 2014 High

    Connected TMEM163 to a known lysosomal channel, revealing it acts cooperatively rather than in isolation to control cellular zinc.

    Evidence Yeast two-hybrid, Co-IP/MS, N-terminal deletion mutagenesis, and zinc assays with TRPML1 co-expression and knockdown in HEK-293 cells

    PMID:25130899

    Open questions at the time
    • Stoichiometry of the TMEM163–TRPML1 interaction unknown
    • Whether interaction modulates transport kinetics not tested
  4. 2016 High

    Resolved the core transport mechanism, showing the protein is a proton-dependent zinc transporter whose dimerization and conserved acidic/histidine residues drive zinc binding.

    Evidence Cell-free synthesis, nanodisc and proteoliposome reconstitution, native MS, and site-directed mutagenesis with FluoZin transport assays

    PMID:27917477

    Open questions at the time
    • High-resolution structure not determined
    • Coupling stoichiometry of H+/Zn2+ not quantified
  5. 2019 High

    Established TMEM163 as a zinc efflux transporter in human cells and placed it phylogenetically in the CDF/SLC30 family with key transport residues identified.

    Evidence Stable/transient expression with two fluorescent zinc dyes and 65Zn radionuclide efflux, D124A/D128A and E286K mutagenesis, and phylogenetics

    PMID:31697912

    Open questions at the time
    • In vivo physiological substrate flux contexts not yet defined
    • Regulation of transporter activity unknown
  6. 2019 Medium

    Linked transporter activity to a physiological output, implicating TMEM163 in zinc-regulated insulin storage and secretion.

    Evidence siRNA knockdown in MIN6 beta cells with zinc, insulin content/secretion, and glucose uptake readouts

    PMID:31813547

    Open questions at the time
    • No reconstitution or mutagenesis to establish direct mechanism
    • Effect on whole-organism glucose homeostasis untested
  7. 2020 Medium

    Revealed a signaling role beyond bulk zinc transport, showing TMEM163 modulates ATP-gated P2X receptor pharmacology and pain behavior.

    Evidence Genome-wide ORF functional screen with channel property assessment and in vivo pain behavioral assays

    PMID:32492420

    Open questions at the time
    • Molecular basis of P2XR modulation not detailed
    • Whether modulation requires zinc transport activity unknown
  8. 2022 High

    Identified TMEM163 as a disease gene, demonstrating that zinc efflux deficiency in oligodendrocytes causes hypomyelinating leukodystrophy.

    Evidence Whole exome sequencing across families, in vitro zinc efflux assays of disease variants, and oligodendroglial expression with myelin gene, branching, and viability readouts; complemented by zebrafish tmem163a/b knockdown with human mRNA rescue

    PMID:35455965 PMID:35953447

    Open questions at the time
    • Mechanism linking neuronal zinc dyshomeostasis to myelin gene downregulation incomplete
    • Variant-specific gain- vs loss-of-function effects on the same disease not reconciled
  9. 2022 Medium

    Showed TMEM163 partners with other zinc transporters, expanding its functional repertoire to heterodimeric efflux units.

    Evidence Reciprocal Co-IP with peptide tags, confocal co-localization, surface biotinylation, and zinc flux assays with ZNT1/2/3

    PMID:36204728

    Open questions at the time
    • Single-lab reciprocal Co-IP
    • ZNT4 heterodimerization not definitively excluded
    • Physiological relevance of specific heterodimers in tissue not shown
  10. 2024 Medium

    Placed TMEM163 in an in vivo neural circuit, showing vesicular zinc release from sensory neurons regulates spinal itch processing.

    Evidence Immunofluorescence, fluorescent zinc imaging, neuron-specific analysis, spinal interneuron electrophysiology, and in vivo zinc chelation in aged mice

    PMID:39602426

    Open questions at the time
    • Abstract-level mechanistic detail
    • Direct requirement of TMEM163 transport activity for itch not fully isolated
  11. 2025 Medium

    Extended the cooperative-transporter model to injury, showing TMEM163–ZnT3 interaction drives zinc dyshomeostasis in ischemic neurons.

    Evidence Co-IP, gain- and loss-of-function in rat primary hippocampal neurons under OGD with FluoZin-3, MTT, TUNEL, and surface biotinylation readouts

    PMID:41504061

    Open questions at the time
    • Single-lab study
    • Trigger for membrane-to-cytoplasm translocation under OGD unknown
  12. 2026 High

    Defined the trafficking logic, showing an N-terminal acidic dileucine motif routes TMEM163 to lysosome-related organelles via competitive, sequential AP-3 and BLOC-1 engagement.

    Evidence Dileucine motif mutagenesis, reciprocal Co-IP across AP and BLOC complexes, confocal localization in trafficking-deficient MEG-01 cells, and proteasome inhibition assays

    PMID:41985787

    Open questions at the time
    • Structural basis of competitive AP-3/BLOC-1 binding not resolved
    • Whether mislocalization alters zinc transport output not measured

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the diverse phenotypes (leukodystrophy, itch, insulin secretion, ischemic injury, P2XR modulation) trace to a single transport mechanism, and whether they require zinc flux versus protein–protein interactions, remains unresolved.
  • No high-resolution structure of the transporter
  • Tissue-specific heterodimer composition not mapped
  • Regulation of transporter activity and trafficking in vivo not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 3
Localization
GO:0005886 plasma membrane 4 GO:0005764 lysosome 2 GO:0005768 endosome 2 GO:0031410 cytoplasmic vesicle 2
Pathway
R-HSA-382551 Transport of small molecules 2 R-HSA-9609507 Protein localization 1

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2014 TMEM163 physically interacts with TRPML1 ion channel, and this interaction depends on TMEM163's N-terminus (deletion of part of the N-terminus disrupts it). TRPML1 co-expression reduces plasma membrane levels of TMEM163, while a PM-retained TRPML1 mutant retains TMEM163 at the PM. TMEM163 knockdown or co-knockdown with TRPML1 causes significantly elevated intracellular zinc levels, demonstrating a cooperative role in cellular zinc homeostasis. Yeast two-hybrid, co-immunoprecipitation, mass spectrometry, confocal microscopy, N-terminal deletion mutagenesis, fluorescent zinc assays, siRNA knockdown in HEK-293 cells Traffic (Copenhagen, Denmark) High 25130899
2007 TMEM163 (SV31) is a synaptic vesicle membrane protein of 31 kDa with six putative transmembrane helices, localized to synaptic vesicles in select brain regions including glutamatergic and GABAergic nerve terminals, as demonstrated by subcellular fractionation, immunocytochemistry of brain sections, and immunoelectron microscopy. Subcellular fractionation, heterologous expression, immunocytochemistry of brain sections, immunoelectron microscopy Journal of neurochemistry High 17623043
2011 TMEM163 (SV31) binds divalent cations Zn2+ and Ni2+ and to a minor extent Cu2+, but not Fe2+, Co2+, Mn2+, or Ca2+. In PC12 cells, SV31-RFP partially co-fractionates with synaptic-like vesicle markers and early endosome marker Rab5, and localizes near the plasma membrane in a compartment positive for SNAP-25 and syntaxin1A. Recombinant protein metal-binding assays, heterologous transfection of PC12 cells, fluorescent zinc indicator (FluoZin-3), sucrose density gradient fractionation, immunocytochemistry Journal of neurochemistry High 21668449
2016 TMEM163 (SV31) assembles into dimers when inserted into nanodisc bilayers, with dimerization increasing Zn2+ binding. Site-directed mutagenesis of two conserved aspartate residues markedly reduces Zn2+ binding but does not affect dimerization. Chemical modification of histidine residues also reduces Zn2+ binding. Reconstituted in proteoliposomes, SV31 mediates proton-dependent Zn2+ transport with a Km of 44.3 μM, requiring external Zn2+ and internal acidic pH. Cell-free protein synthesis, nanodisc reconstitution, site-directed mutagenesis, native mass spectrometry, proteoliposome transport assay with FluoZin-1 Journal of neurochemistry High 27917477
2019 Human TMEM163 functions as a zinc efflux transporter in cells. Cells stably or transiently expressing TMEM163 show significantly reduced intracellular zinc levels as measured by two fluorescent zinc dyes and radionuclide 65Zn. Alanine substitution of two conserved aspartate residues (D124A/D128A) or the E286K variant significantly reduces zinc efflux, establishing these residues as important for transport function. Phylogenetic analysis places TMEM163 within the CDF/SLC30 zinc efflux family. Stable and transient expression in human cell lines, fluorescent zinc dyes (two independent), 65Zn radionuclide assay, TPEN chelation control, site-directed mutagenesis, sequence alignment and phylogenetics Archives of biochemistry and biophysics High 31697912
2019 Knockdown of endogenous Tmem163 in MIN6 pancreatic beta cells results in increased intracellular zinc, increased total insulin content, but compromised glucose-stimulated insulin secretion and enhanced cellular glucose uptake, placing TMEM163 in the pathway of zinc-regulated insulin storage and secretion. siRNA knockdown in MIN6 cells, intracellular zinc measurement, insulin content and secretion assays, glucose uptake assay Biochemical and biophysical research communications Medium 31813547
2020 TMEM163 specifically modulates the channel properties and pharmacology of ATP-gated P2X receptors (P2XRs) in vivo. Genome-wide ORF screening identified TMEM163 as a P2XR modulator; it is required for full function of neuronal P2XR and pain-related ATP-evoked behavior. Genome-wide ORF functional screen, electrophysiology (implied by channel property assessment), in vivo behavioral assays for pain Cell reports Medium 32492420
2022 Heterozygous missense variants in TMEM163 residing in the conserved cytoplasmic domain cause hypomyelinating leukodystrophy. Functional in vitro analysis shows significant impairment of zinc efflux by mutant proteins. Expression of mutant TMEM163 in an oligodendroglial cell line reduces mRNA expression of key myelin genes, decreases branching, and increases cell death, establishing a role for TMEM163-mediated zinc efflux in oligodendrocyte development. Whole exome sequencing, in vitro zinc efflux assays with disease variants, oligodendroglial cell line expression, qPCR for myelin genes, cell morphology and viability assays Brain : a journal of neurology High 35953447
2022 Two de novo TMEM163 variants (L76R, L76P) cause hypomyelinating leukodystrophy. Functional zinc flux assays show L76R attenuates and L76P enhances zinc efflux. In zebrafish, knockdown of tmem163a/b causes myelin deficit, locomotor disability, and oligodendrocyte/neuron loss; wild-type human TMEM163 rescues the morphant phenotype, while L76R and L76P mutants fail to rescue or worsen it. TMEM163 localizes to the plasma membrane, lysosomes, early endosomes, and other vesicular compartments. Functional zinc flux assays (HeLa stable expression), zebrafish morphant model (siRNA knockdown of tmem163a/b), mRNA rescue experiments, locomotor assays, immunostaining for myelin and oligodendrocyte markers Cells High 35455965
2022 TMEM163 forms homodimers and heterodimerizes with ZNT1, ZNT2, and ZNT3, but not with ZNT4 (negative control for heterodimerization was not excluded). TMEM163 and ZNT proteins partially co-localize in cells. TMEM163/ZNT heterodimers exhibit similar zinc efflux function as TMEM163 homodimers. Plasma membrane localization of TMEM163 is not markedly altered by ZNT co-expression. Co-immunoprecipitation with unique peptide tags, Western blot, confocal microscopy co-localization, cell surface biotinylation, functional zinc flux assays (FluoZin-3, Newport Green) Biochemistry and biophysics reports Medium 36204728
2024 TMEM163 is expressed in a subset of dorsal root ganglion neurons enriched with vesicular Zn2+. These neurons form direct synapses with spinal NPY+ inhibitory interneurons and modulate their activity. In aged mice, TMEM163 expression and vesicular Zn2+ concentration are elevated in central terminals of TMEM163+ afferents; excessive vesicular Zn2+ release dampens NPY+ interneuron activity, causing disinhibition of itch circuits and chronic itch. Zinc chelation in the spinal dorsal horn relieves itch in aged mice. Immunofluorescence, fluorescent zinc imaging, conditional knockout/neuron-specific analysis, electrophysiology of spinal interneurons, zinc chelation pharmacology in vivo (aged mice) PLoS biology Medium 39602426
2025 ZnT3 and TMEM163 physically interact (co-immunoprecipitation confirmed) and cooperatively regulate zinc homeostasis in hippocampal neurons. Under oxygen-glucose deprivation (OGD), both proteins are upregulated and translocate from the cell membrane to the cytoplasm. Overexpression of TMEM163 exacerbates extracellular zinc efflux and neuronal apoptosis under OGD; silencing attenuates zinc overload and neurodegeneration. TMEM163 thus contributes to ischemia-induced neuronal injury via zinc dyshomeostasis. siRNA silencing and plasmid overexpression in rat primary hippocampal neurons, OGD model, MTT assay, TUNEL staining, FluoZin-3 zinc measurement, ELISA, co-immunoprecipitation, cell surface biotinylation, RT-qPCR, Western blot Frontiers in bioscience (Landmark edition) Medium 41504061
2026 A conserved N-terminal acidic dileucine motif (LEDRGL69L70) in TMEM163 is essential for interaction with BLOC-1 and AP-3 complexes but dispensable for binding AP-1, AP-2, and BLOC-2. Mutation of this motif causes TMEM163 accumulation at the plasma membrane. Loss of BLOC-1 or AP-3 enhances TMEM163 binding to the other complex and results in differential abnormal endo-lysosomal localization, indicating competitive binding and sequential sorting of TMEM163 by AP-3 and BLOC-1 to platelet dense granules. TMEM163 is degraded via the proteasome in cells lacking AP-1, AP-2, AP-3, BLOC-1, or BLOC-2. Co-immunoprecipitation, mutagenesis of dileucine motif, confocal microscopy subcellular localization, MEG-01 cell lines deficient in endosomal trafficking complexes, proteasome inhibition assays, cell surface biotinylation The Journal of biological chemistry High 41985787

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 Cellular zinc levels are modulated by TRPML1-TMEM163 interaction. Traffic (Copenhagen, Denmark) 52 25130899
2019 Transmembrane 163 (TMEM163) protein effluxes zinc. Archives of biochemistry and biophysics 29 31697912
2007 Identification and characterization of SV31, a novel synaptic vesicle membrane protein and potential transporter. Journal of neurochemistry 29 17623043
2017 The mucolipin-1 (TRPML1) ion channel, transmembrane-163 (TMEM163) protein, and lysosomal zinc handling. Frontiers in bioscience (Landmark edition) 24 28199205
2011 SV31 is a Zn2+-binding synaptic vesicle protein. Journal of neurochemistry 21 21668449
2016 The synaptic vesicle protein SV31 assembles into a dimer and transports Zn2. Journal of neurochemistry 19 27917477
2022 Variants in the zinc transporter TMEM163 cause a hypomyelinating leukodystrophy. Brain : a journal of neurology 18 35953447
2020 TMEM163 Regulates ATP-Gated P2X Receptor and Behavior. Cell reports 17 32492420
2021 Transmembrane 163 (TMEM163) Protein: A New Member of the Zinc Efflux Transporter Family. Biomedicines 16 33670071
2019 Role of Tmem163 in zinc-regulated insulin storage of MIN6 cells: Functional exploration of an Indian type 2 diabetes GWAS associated gene. Biochemical and biophysical research communications 12 31813547
2022 Functional Study of TMEM163 Gene Variants Associated with Hypomyelination Leukodystrophy. Cells 9 35455965
2019 Polymorphisms of ACMSD-TMEM163, MCCC1, and BCKDK-STX1B Are Not Associated with Parkinson's Disease in Taiwan. Parkinson's disease 8 30719275
2022 Transmembrane 163 (TMEM163) protein interacts with specific mammalian SLC30 zinc efflux transporter family members. Biochemistry and biophysics reports 5 36204728
2022 PPARG, TMEM163, UBE2E2, and WFS1 Gene Polymorphisms Are Not Significant Risk Factors for Gestational Diabetes in the Polish Population. Journal of personalized medicine 4 35207731
2024 Elevated vesicular Zn2+ in dorsal root ganglion neurons expressing the transporter TMEM163 causes age-associated itchy skin in mice. PLoS biology 3 39602426
2024 The role of TMEM163 protein in thyroid microcarcinoma: expression pattern and clinical implications. Journal of endocrinological investigation 1 39352626
2026 A dileucine motif in TMEM163 is essential for its binding with both AP-3 and BLOC-1 complex. The Journal of biological chemistry 0 41985787
2025 ZnT3-TMEM163 Mediates Zinc Homeostasis Imbalance Induced Neurodegeneration in Hippocampus. Frontiers in bioscience (Landmark edition) 0 41504061

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