SLC30A5

SLC30A5 (ZnT5) is a zinc transporter of the early secretory pathway that supplies Zn2+ to zinc-requiring enzymes and thereby controls secretory-pathway and immune functions (PMID:15525635, PMID:38762179). ZnT5 forms obligate heterodimers with ZnT6, with specificity determined by the cytosolic C-terminal tail of ZnT5, and this ZnT5-ZnT6 unit—redundantly with ZnT7—loads zinc onto GPI-anchored alkaline phosphatases to convert apo- to holo-enzyme and onto Golgi α-mannosidase II, which is required for conversion of hybrid- to complex-type N-glycans (PMID:15525635, PMID:19759014, PMID:38762179). Its conserved cation efflux domain is required for transport activity, and it localizes to ER versus Golgi according to alternative C-terminal splice variants carrying distinct ER-retention and Golgi-targeting signals (PMID:21887337, PMID:39790720). Beyond enzyme metalation, ZnT5 controls cytoplasmic zinc pools and supports growth hormone secretion (PMID:25196974), and in mast cells it mediates FcεRI-induced PKC translocation to the plasma membrane and NF-κB nuclear translocation, selectively enabling delayed-type but not immediate-type allergic responses (PMID:19451265). In vivo loss of ZnT5 causes osteopenia from impaired osteoblast-to-osteocyte maturation and male-specific bradyarrhythmia and sudden cardiac death (PMID:12095919). A bi-allelic in-frame deletion in the cation efflux domain lowers cytosolic zinc and causes a syndrome of severe neonatal hypotonia with respiratory failure (PMID:39790720).

1. 2002 High

   Establishing that ZnT5 has non-redundant physiological roles, knockout mice revealed defined organ-level phenotypes and placed the transporter upstream of cardiac transcriptional programs.

   Evidence Znt5-knockout mice with bone density measurement and cardiac gene-expression microarray profiling

   PMID:12095919

   Open questions at the time

   • Molecular link between zinc transport and immediate-early/heat-shock gene downregulation not defined
   • Basis for male-specific cardiac phenotype unexplained
2. 2004 High

   To define a molecular function, gene disruption showed ZnT5 (with ZnT7) is required to metalate alkaline phosphatases, identifying enzyme activation in the secretory pathway as its biochemical role.

   Evidence Gene disruption in DT40 cells with ALP activity assay and overexpression rescue

   PMID:15525635

   Open questions at the time

   • Did not resolve oligomeric state of the functional transporter
   • Direction and energetics of zinc transport not measured
3. 2007 High

   Addressing how ZnT5 expression and localization are controlled, splice variants were shown to differ in localization and the gene's transcription to be repressed by both high and low zinc with opposing mRNA stabilization.

   Evidence GFP-fusion imaging in CHO cells, promoter-deletion reporter assays, and actinomycin D mRNA stability assays

   PMID:17234632

   Open questions at the time

   • Trans-acting factors binding the -154/+50 zinc-responsive element not identified
   • Mechanism of zinc-dependent mRNA stabilization unknown
4. 2009 High

   Resolving the functional unit, reciprocal Co-IP and chimera analysis established ZnT5-ZnT6 as obligate heterodimers and mapped the ZnT5 C-terminal tail as the determinant of partner specificity.

   Evidence Co-immunoprecipitation, transmembrane-residue mutagenesis, and chimera studies in DT40 cells deficient in ZnT5/6/7

   PMID:19759014

   Open questions at the time

   • Stoichiometry and structure of the heterodimer not solved
   • How the heterodimer coordinates zinc differently from ZnT homo-oligomers not fully defined
5. 2009 High

   Extending function to immune signaling, knockout and translocation assays showed ZnT5 is required for FcεRI-driven PKC and NF-κB translocation and selectively for delayed-type allergy.

   Evidence Znt5-knockout mice, anaphylaxis and contact hypersensitivity models, PKC/NF-κB translocation assays, PKC zinc-finger mutagenesis

   PMID:19451265

   Open questions at the time

   • Subcellular site where ZnT5-supplied zinc acts on PKC not pinpointed
   • Why immediate-type degranulation is spared not explained
6. 2011 Medium

   To explain variant localization, domain swapping identified specific exon-encoded C-terminal Golgi-targeting and ER-retention signals dictating ER versus Golgi residence.

   Evidence N-/C-terminal GFP/FLAG fusion imaging and deletion/chimera analysis of splice variants

   PMID:21887337

   Open questions at the time

   • Functional consequences of differential ER vs Golgi localization not tested
   • Single-lab imaging without orthogonal endogenous validation
7. 2014 Medium

   Linking ZnT5 to endocrine secretion, knockdown reduced growth hormone release and altered the cytoplasmic zinc pool, implicating ZnT5 in zinc influx into secretory compartments.

   Evidence Confocal co-localization, siRNA knockdown, GH secretion Western blot, luciferase cytoplasmic Zn2+ reporter in GH3 cells

   PMID:25196974

   Open questions at the time

   • Direct mechanism connecting zinc transport to GH secretion not established
   • Single cell-line system
8. 2015 Low

   Probing human disease relevance, reduced SLC30A5 expression with promoter CpG hypermethylation was associated with a maternal milk zinc deficiency disorder.

   Evidence mRNA/protein quantification and bisulfite sequencing of SLC30A5 promoter in patient-derived lymphoblasts/fibroblasts

   PMID:26319140

   Open questions at the time

   • Correlative without functional rescue demonstrating causality
   • Methylation-to-phenotype causal chain not established
9. 2024 High

   Defining a glycosylation function, KO and glycan profiling showed ZnT5-6 and ZnT7 supply zinc to Golgi α-mannosidase II, controlling hybrid- to complex-type N-glycan conversion.

   Evidence Gene disruption of ZNT5/6/7, GMII enzymatic assay, N-glycan profiling with LAMAN control, xenograft assay

   PMID:38762179

   Open questions at the time

   • Full repertoire of zinc-dependent secretory enzymes served by ZnT5 not enumerated
   • Tumor-growth mechanism downstream of glycan changes not dissected
10. 2024 Medium

    Implicating ZnT5 in cancer cell behavior, knockdown promoted migration and EMT via a SMAD1-dependent route blocked by dorsomorphin.

    Evidence siRNA knockdown, wound-healing assay, EMT-marker Westerns, antibody array, dorsomorphin inhibition in breast cancer cells

    PMID:39138630

    Open questions at the time

    • How zinc transport mechanistically alters SMAD1 not defined
    • Single-lab in vitro only
11. 2025 Medium

    Confirming the catalytic core, a bi-allelic in-frame deletion in the conserved cation efflux domain lowered cytosolic zinc and caused severe neonatal hypotonia, tying domain function to human disease.

    Evidence Homozygosity mapping, exome sequencing, and variant transfection into HEK293 cells with cytosolic zinc monitoring

    PMID:39790720

    Open questions at the time

    • Single variant without broader mutagenesis panel
    • Tissue basis of neonatal hypotonia phenotype not established
12. 2026 Low

    Extending to oncogenic signaling, SLC30A5-mediated zinc transport was linked to PTP/AKT/ESR1 signaling with an ESR1-driven transcriptional feedback loop in ER+ breast cancer.

    Evidence Combined bioinformatic and experimental analyses in ER+ breast cancer cells (methods not detailed in abstract)

    PMID:41790496

    Open questions at the time

    • Assay details and direct zinc-PTP-AKT link not specified
    • No replication or in vivo validation

• How zinc supply through ZnT5-ZnT6 is mechanistically coupled to its diverse downstream outputs—cardiac transcription, PKC/NF-κB signaling, GH secretion, and EMT—remains unresolved.
• No structural model of the ZnT5-ZnT6 transporter
• Full substrate enzyme set incompletely defined
• Mechanistic links to signaling pathways largely correlative