Affinage

SLC30A4

Probable proton-coupled zinc antiporter SLC30A4 · UniProt O14863

Length
429 aa
Mass
47.5 kDa
Annotated
2026-04-28
19 papers in source corpus 12 papers cited in narrative 12 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SLC30A4 (ZnT4) is a vesicular zinc transporter that loads zinc from the cytoplasm into the trans-Golgi network, lysosomes, and secretory granules, thereby supporting zinc-dependent enzyme metallation, organellar zinc storage, and regulated zinc secretion. Cryo-EM reveals ZnT4 as a dimeric H⁺/Zn²⁺ antiporter that undergoes transmembrane conformational changes between outward- and inward-facing states to drive zinc translocation (PMID:39474773). At the trans-Golgi network, ZnT4 supplies zinc required for activation of galactosyltransferase, carbonic anhydrase VI, and tissue-nonspecific alkaline phosphatase (TNAP), with zinc-transport-incompetent mutants failing to rescue TNAP activity (PMID:22621784, PMID:24204829). ZnT4 also mediates lysosomal zinc storage in concert with the channel TRPML1 (PMID:23368743), maintains mast cell granule zinc pools that suppress caspase activation (PMID:15187159), and is essential for mammary gland zinc secretion into milk, as ZnT4-null mice exhibit defective lactation and precocious mammary involution (PMID:26538236).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 1999 Medium

    Establishing ZnT4 as a polytopic membrane protein on intracellular vesicles with distinct zinc-binding and protein-interaction domains resolved its basic subcellular topology and implicated it in vesicular zinc trafficking.

    Evidence Subcellular fractionation, immunofluorescence, and GST-fusion pulldowns in Caco-2 enterocytes

    PMID:10600821

    Open questions at the time
    • No zinc transport activity directly measured
    • Endosomal colocalization with AP-1/AP-2 not functionally tested
    • Sorting signals governing vesicular targeting undefined
  2. 2004 Medium

    Identifying ZnT4 as the vesicular zinc transporter in mast cell granules linked its transport function to a specific immunological outcome — granule zinc restrains caspase activation and NF-κB translocation, establishing ZnT4 as a regulator of mast cell survival signaling.

    Evidence Immunogold EM, Zinquin fluorescence, TPEN chelation, and caspase/NF-κB assays in mast cells

    PMID:15187159

    Open questions at the time
    • ZnT4 knockdown/knockout not performed in mast cells
    • Whether other ZnTs contribute to granule zinc loading not excluded
    • Mechanism by which granule zinc inhibits caspases not defined
  3. 2012 High

    Demonstrating that ZnT4 at the trans-Golgi network directly supplies zinc for metallation of galactosyltransferase and carbonic anhydrase VI established its role as a Golgi zinc loader essential for secretory enzyme activation.

    Evidence ZnT4 overexpression and knockdown in HC11 mammary cells with FluoZin3 zinc measurement and enzyme activity assays

    PMID:22621784

    Open questions at the time
    • Structural basis for Golgi targeting unknown
    • Contribution of other ZnTs to Golgi zinc pool not quantified
  4. 2013 High

    Two studies resolved ZnT4's role in lysosomal zinc homeostasis and secretory pathway enzyme metallation: ZnT4 works with TRPML1 to regulate lysosomal zinc retention, and its zinc transport activity is required for TNAP activation as shown by transport-incompetent mutant rescue experiments in triple-knockout cells.

    Evidence siRNA epistasis of ZnT4 and TRPML1 with lysosomal phenotyping; genetic rescue of ZnT1⁻/⁻ MT⁻/⁻ ZnT4⁻/⁻ cells with wild-type vs. transport-dead ZnT4 mutants and TNAP activity readout

    PMID:23368743 PMID:24204829

    Open questions at the time
    • TRPML1–ZnT4 physical interaction not shown
    • Identity of zinc-binding residues critical for transport defined genetically but not structurally
  5. 2015 Medium

    Analysis of ZnT4-null (lm/lm) mice revealed that loss of ZnT4 causes defective mammary zinc secretion, decreased Akt/STAT5 signaling, and premature mammary involution, establishing ZnT4 as physiologically essential for lactation.

    Evidence Histology and Western blot of signaling proteins in lm/lm mouse mammary glands

    PMID:26538236

    Open questions at the time
    • Whether signaling changes are direct or secondary to zinc depletion not resolved
    • Milk zinc content not quantified in this study
  6. 2016 Medium

    Placing SLC30A4 downstream of IL-4 signaling in macrophages showed it increases the labile intracellular zinc pool, which promotes survival of intracellular pathogens — connecting ZnT4 to innate immune zinc handling.

    Evidence siRNA knockdown of SLC30A4 in macrophages with zinc fluorescence, intracellular pathogen survival assays, and murine in vivo model

    PMID:27653687

    Open questions at the time
    • Mechanism of IL-4-mediated SLC30A4 upregulation not defined
    • Directionality of ZnT4-mediated zinc flux in macrophages unclear given canonical vesicular loading role
  7. 2020 Medium

    Two independent studies further characterized ZnT4's lysosomal zinc-loading function and identified miR-30a as a direct negative regulator of ZnT4: knockdown increases cytosolic zinc and multi-vesicular bodies in prostate cells, while miR-30a-mediated ZnT4 suppression in endothelial cells causes zinc accumulation and blood-brain barrier disruption during ischemia.

    Evidence ZnT4 mRNA knockdown with FluoZin-1 and EM in PNT1A cells; luciferase reporter assay confirming miR-30a targets ZnT4 3′UTR, ZnT4 rescue, and BBB permeability in murine MCAO model

    PMID:32501158 PMID:33140261

    Open questions at the time
    • miR-30a–ZnT4 axis not validated in non-endothelial contexts
    • Lysosomal zinc measurement not performed directly in prostate knockdown cells
  8. 2023 Medium

    Linking ZnT4 to testosterone biosynthesis via the PI3K/Akt/mTOR pathway showed that ZnT4 knockdown in Leydig cells causes zinc accumulation, apoptosis, and reduced StAR/3β-HSD expression, with rapamycin epistasis confirming mTORC1 involvement.

    Evidence siRNA knockdown in TM3 Leydig cells with testosterone ELISA, Western blot, and pathway inhibitor experiments

    PMID:37733161

    Open questions at the time
    • Whether ZnT4 acts directly on mTOR or via zinc-dependent intermediaries not resolved
    • In vivo reproductive phenotype of ZnT4 loss not examined
  9. 2024 High

    Cryo-EM structure of human ZnT4 in the outward-facing conformation established the molecular architecture of its H⁺/Zn²⁺ antiport mechanism and, by comparison with inward-facing ZnT3, defined the transmembrane conformational changes that drive zinc translocation.

    Evidence Cryo-EM structure determination of human ZnT4 and ZnT3 with comparative structural analysis

    PMID:39474773

    Open questions at the time
    • Inward-facing structure of ZnT4 itself not yet captured
    • Proton coupling stoichiometry not experimentally measured
    • Dimerization interface functional significance not tested by mutagenesis

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the structural determinants of ZnT4's organelle-specific targeting (Golgi vs. lysosome vs. plasma membrane), the stoichiometry and energetics of H⁺/Zn²⁺ coupling, and how ZnT4 is regulated at the protein level beyond miR-30a-mediated transcriptional control.
  • Sorting signals for differential organellar targeting not identified
  • No reconstituted transport assay measuring H⁺/Zn²⁺ stoichiometry
  • Post-translational regulatory mechanisms unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 3 GO:0140657 ATP-dependent activity 1
Localization
GO:0005794 Golgi apparatus 3 GO:0031410 cytoplasmic vesicle 3 GO:0005764 lysosome 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-168256 Immune System 2 R-HSA-162582 Signal Transduction 1
Partners
MT3TRPML1ZNT1

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 ZnT4/Dri27 is a polytopic membrane protein localized to intracellular vesicles concentrated in the basal cytoplasm of polarized enterocytes; it partially colocalizes with the transferrin receptor and clathrin adaptor complexes AP-1 and AP-2 in endosomal vesicles; distinct protein domains function as zinc-binding and protein-protein interaction domains. Subcellular fractionation, immunofluorescence, GST-fusion domain pulldown assays, transient transfection of myc-tagged construct in Caco-2 cells The American journal of physiology Medium 10600821
2003 ZnT4 protein localizes to intracellular vesicles and the plasma membrane in prostate epithelial cells, consistent with a role in vesicular zinc transport to the cell membrane and zinc efflux. Immunofluorescence and surface biotinylation in ZnT4-expressing cells Oncogene Medium 12955079
2004 ZnT4 is the vesicular zinc transporter in mast cell granules; it mediates zinc uptake into granules, and granule zinc inhibits caspase activation and NF-κB nuclear translocation; chelation of granule zinc (but not degranulation) activates caspases and promotes NF-κB translocation. Zinquin fluorescence, immunofluorescence, immunogold labeling, TPEN chelation, fluorogenic caspase substrate assay, IgE/anti-IgE activation Journal of immunology Medium 15187159
2012 ZnT4 is localized to the trans-Golgi network (TGN) and cell membrane in mammary epithelial cells, transports zinc from the cytoplasm into the TGN, directly contributes to labile zinc accumulation in the TGN, and provides zinc for metallation of galactosyltransferase and carbonic anhydrase VI; ZnT4 relocalizes to the cell membrane in response to elevated zinc. Fluorescence localization, FluoZin3 fluorescence assay, ZnT4 overexpression and knockdown in HC11 cells, galactosyltransferase and carbonic anhydrase VI activity assays American journal of physiology. Cell physiology High 22621784
2013 ZnT4 works in concert with the lysosomal channel TRPML1 to regulate zinc translocation between the cytoplasm and lysosomes; ZnT4 knockdown ameliorates lysosomal enlargement caused by TRPML1 knockdown under high-zinc conditions, placing ZnT4 downstream of TRPML1-mediated lysosomal zinc retention. siRNA knockdown of TRPML1 and ZnT4, LysoTracker and zinc staining, MTF-1 and MT2a transcriptional reporter assays The Biochemical journal Medium 23368743
2013 ZnT4, together with ZnT1 and metallothionein, cooperatively handles cytoplasmic zinc that is required for full activation of tissue-nonspecific alkaline phosphatase (TNAP) in the early secretory pathway; zinc-transport-incompetent mutants of ZnT4 fail to rescue TNAP activity, demonstrating that ZnT4's zinc transport function is essential for zinc enzyme metallation. Gene disruption (ZnT1−/− MT−/− ZnT4−/− triple-knockout cells), re-expression of wild-type and transport-incompetent mutants, TNAP enzymatic activity assay, cytosolic zinc measurement PloS one High 24204829
2015 ZnT4 (SLC30A4) transports zinc into the trans-Golgi apparatus for lactose synthesis and across the apical membrane for zinc efflux into milk; loss of ZnT4 in lm/lm mice decreases Akt expression, STAT5 activation (indicative of secretory defects), and increases ZnT2, TNF-α, cleaved e-cadherin, and STAT3 activation (indicative of precocious involution). ZnT4-null (lm/lm) mouse model, histology, Western blot for signaling proteins (Akt, STAT5, STAT3, e-cadherin), mammary gland morphology American journal of physiology. Regulatory, integrative and comparative physiology Medium 26538236
2016 IL-4 induces a SLC30A4-dependent increase in the labile intracellular Zn2+ pool in macrophages by shuttling extracellular zinc into cells; SLC30A4 and metallothionein 3 (MT3) together dictate the size of this labile Zn2+ pool, which promotes survival of intracellular pathogens. siRNA knockdown of SLC30A4 and MT3 in macrophages, labile zinc fluorescence measurement, intracellular pathogen survival assays, in vivo murine model Cell reports Medium 27653687
2020 ZnT4 is a direct negative regulatory target of miR-30a; miR-30a suppresses ZnT4 expression, leading to intracellular zinc accumulation in endothelial cells, degradation of tight junction proteins, and increased blood-brain barrier permeability during ischemic stroke; restoring ZnT4 by miR-30a inhibition reduces zinc accumulation and prevents BBB damage. Luciferase reporter assay (direct miR-30a targeting of ZnT4 3'UTR), ZnT4 knockdown and overexpression, BBB permeability assay, tight junction protein immunoblot, miR-30a inhibitor in murine MCAO model Journal of cerebral blood flow and metabolism Medium 32501158
2020 In prostate epithelial cells, ZnT4 mediates lysosomal zinc storage; ZnT4 knockdown increases multi-vesicular body formation and cytosolic zinc levels, while ZnT1 is the primary zinc efflux transporter responsible for glucose-stimulated zinc secretion. ZnT4 and ZnT1 mRNA knockdown in PNT1A cells, FluoZin-1-AM intracellular zinc fluorescence, Bafilomycin A1 lysosome disruption, electron microscopy of intracellular zinc storage Molecular imaging and biology Medium 33140261
2023 ZnT4 knockdown in mouse Leydig (TM3) cells causes intracellular zinc accumulation, reduced cell viability, apoptosis, decreased testosterone concentration, and downregulation of testosterone synthesis proteins StAR and 3β-HSD; ZnT4 promotes testosterone synthesis through the PI3K/Akt/mTOR autophagy pathway, as mTORC1 inhibition (rapamycin) blocks the testosterone decrease caused by ZnT4 knockdown. siRNA knockdown in TM3 cells, testosterone ELISA, Western blot for StAR and 3β-HSD, PI3K/Akt/mTOR pathway inhibitors, hCG rescue experiment In vitro cellular & developmental biology. Animal Medium 37733161
2024 Cryo-EM structures of human ZnT4 (outward-facing conformation) reveal its architecture as an H+/Zn2+ antiporter; comparison with the inward-facing ZnT3 structure identifies conformational changes within the transmembrane domain that underlie the Zn2+ transport mechanism. Cryo-electron microscopy structure determination of human ZnT4 and ZnT3, comparative structural analysis of conformational states FEBS letters High 39474773

Source papers

Stage 0 corpus · 19 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1999 Cloning, expression, and vesicular localization of zinc transporter Dri 27/ZnT4 in intestinal tissue and cells. The American journal of physiology 104 10600821
2003 Expression of the zinc transporter ZnT4 is decreased in the progression from early prostate disease to invasive prostate cancer. Oncogene 92 12955079
2004 Labile zinc and zinc transporter ZnT4 in mast cell granules: role in regulation of caspase activation and NF-kappaB translocation. Journal of immunology (Baltimore, Md. : 1950) 70 15187159
2013 Zinc-dependent lysosomal enlargement in TRPML1-deficient cells involves MTF-1 transcription factor and ZnT4 (Slc30a4) transporter. The Biochemical journal 64 23368743
2012 ZnT4 provides zinc to zinc-dependent proteins in the trans-Golgi network critical for cell function and Zn export in mammary epithelial cells. American journal of physiology. Cell physiology 57 22621784
2016 IL-4 Induces Metallothionein 3- and SLC30A4-Dependent Increase in Intracellular Zn(2+) that Promotes Pathogen Persistence in Macrophages. Cell reports 40 27653687
2020 MicroRNA-30a regulates acute cerebral ischemia-induced blood-brain barrier damage through ZnT4/zinc pathway. Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism 32 32501158
2013 Cooperative functions of ZnT1, metallothionein and ZnT4 in the cytoplasm are required for full activation of TNAP in the early secretory pathway. PloS one 31 24204829
2011 Apical localization of zinc transporter ZnT4 in human airway epithelial cells and its loss in a murine model of allergic airway inflammation. Nutrients 20 22254085
2001 Expression pattern, genomic structure and evaluation of the human SLC30A4 gene as a candidate for acrodermatitis enteropathica. Human genetics 17 11511923
2006 The Znt4 mutation inlethal milk mice affects intestinal zinc homeostasis through the expression of other Zn transporters. Genes & nutrition 15 18850221
2015 ZnT4 (SLC30A4)-null ("lethal milk") mice have defects in mammary gland secretion and hallmarks of precocious involution during lactation. American journal of physiology. Regulatory, integrative and comparative physiology 14 26538236
2020 The Roles of ZnT1 and ZnT4 in Glucose-Stimulated Zinc Secretion in Prostate Epithelial Cells. Molecular imaging and biology 12 33140261
2001 Genomic localization, organization and amplification of the human zinc transporter protein gene, ZNT4, and exclusion as a candidate gene in different clinical variants of acrodermatitis enteropathica. Archives of dermatological research 12 11686514
2023 Knockdown of ZnT4 Induced Apoptosis, Inhibited Proliferation and testosterone synthesis of TM3 cells. In vitro cellular & developmental biology. Animal 6 37733161
2003 Mutation analysis of the zinc transporter gene SLC30A4 reveals no association with periodic catatonia on chromosome 15q15. Journal of neural transmission (Vienna, Austria : 1996) 6 14628196
2024 Cryo-EM structures of the zinc transporters ZnT3 and ZnT4 provide insights into their transport mechanisms. FEBS letters 5 39474773
2024 Transcriptional regulation of Znt family members znt4, znt5 and znt10 and their function in zinc transport in yellow catfish (Pelteobagrus fulvidraco). Biochimica et biophysica acta. Gene regulatory mechanisms 4 38740364
2024 SLC30A4-AS1 Mediates the Senescence of Periodontal Ligament Stem Cells in Inflammatory Environments via the Alternative Splicing of TP53BP1. Cell proliferation 3 39572253