SLC38A6

SLC38A6 (SNAT6) is a sodium-dependent glutamine and glutamate transporter that links amino acid transport to glutamatergic neurotransmission, tumor metabolism, and inflammatory and injury responses (PMID:33503881, PMID:35901507). In the brain it is expressed selectively in excitatory neurons and localizes to synaptic membranes (PMID:24752331), where it resides at caveolin-rich plasma membrane sites and undergoes substrate- and sodium-dependent internalization through formation of SNAT6-caveolin complexes (PMID:33503881). At the presynaptic terminal it associates with phosphate-activated glutaminase, synaptophysin, CTP synthase 2, and metabotropic glutamate receptor 2, positioning it within the glutamate-glutamine cycle by cycling between cytoplasm and plasma membrane according to substrate availability (PMID:33503881). Beyond the synapse, SLC38A6 supports glutamine metabolism and mitochondrial respiration in hepatocellular carcinoma cells, where its expression is driven by promoter H3K27 acetylation laid down by EP300 (PMID:35901507) and by a ZNF652-circRHOT1-KAT5 axis that increases promoter H3K27ac to promote proliferation and suppress apoptosis (PMID:41311269). In macrophages it acts downstream of TLR4 signaling to promote pro-inflammatory cytokine production (PMID:36707853), and in renal tubular cells it promotes apoptosis and suppresses fatty acid β-oxidation during cisplatin-induced acute kidney injury (PMID:41885504).

1. 2014 Medium

   Establishing where SNAT6 acts in the brain narrowed its physiological context from an orphan transporter to a candidate synaptic protein.

   Evidence Immunohistochemistry and proximity ligation assay with synaptic markers in mouse brain

   PMID:24752331

   Open questions at the time

   • Transport substrates and activity not yet demonstrated
   • No functional consequence of synaptic localization tested
2. 2021 Medium

   Identifying SNAT6 as a sodium-dependent glutamine/glutamate transporter that internalizes via caveolin complexes defined both its biochemical activity and a regulated trafficking mechanism.

   Evidence Tritium-labeled amino acid uptake assays, homology modeling, and co-IP/PLA for SNAT6-caveolin interaction

   PMID:33503881

   Open questions at the time

   • Transport kinetics and stoichiometry not fully quantified
   • Caveolin interaction shown by indirect PLA/co-IP without structural detail
3. 2021 Medium

   Mapping presynaptic interaction partners placed SNAT6 mechanistically within the glutamate-glutamine cycle.

   Evidence Co-expression, co-localization, and PLA for Pag, synaptophysin, CTPs2, and Grm2 at presynaptic terminals

   PMID:33503881

   Open questions at the time

   • Interactions inferred from indirect proximity methods, not direct binding
   • Functional flux through the cycle not measured
4. 2022 Medium

   Linking EP300-mediated promoter H3K27ac to SLC38A6 expression connected transporter levels to glutamine metabolism and mitochondrial respiration in cancer.

   Evidence ChIP, EP300 silencing, siRNA knockdown, and metabolic assays in hepatocellular carcinoma cells

   PMID:35901507

   Open questions at the time

   • Direct transport contribution to the metabolic phenotype not isolated
   • In vivo tumor relevance not tested
5. 2023 Medium

   Genetic and pharmacological epistasis placed SLC38A6 downstream of TLR4 and upstream of pro-inflammatory cytokine production in macrophages.

   Evidence Conditional and systemic knockout mice, TLR4 inhibitor and knockout, flow cytometry, and cytokine measurement in pulmonary inflammation models

   PMID:36707853

   Open questions at the time

   • Molecular mechanism linking transport activity to cytokine production unresolved
   • Whether glutamine/glutamate flux drives the inflammatory phenotype not directly shown
6. 2025 Medium

   A ZNF652-circRHOT1-KAT5 axis was defined as an additional epigenetic route activating SLC38A6 to promote HCC proliferation, extending the transcriptional regulatory picture.

   Evidence ChIP for H3K27ac/KAT5 occupancy, knockdown, overexpression rescue, and luciferase/binding assays in HCC cells

   PMID:41311269

   Open questions at the time

   • Relationship between this axis and EP300-mediated regulation not integrated
   • Transport-dependence of proliferative effect not separated from regulatory effect
7. 2026 High

   Tubular-specific knockout established SLC38A6 as a context-specific promoter of apoptosis and suppressor of fatty acid β-oxidation in cisplatin-induced acute kidney injury.

   Evidence KspCre conditional knockout mice, HK-2 knockdown, transcriptome sequencing, lipid and FAO enzyme assays, and TUNEL staining

   PMID:41885504

   Open questions at the time

   • Mechanism connecting transport activity to FAO suppression unresolved
   • Whether the effect is specific to cisplatin injury or generalizes to other AKI models untested

• How SLC38A6's core transport activity mechanistically drives its divergent roles across synapse, tumor, macrophage, and kidney remains unresolved.
• No structural model of substrate binding and translocation
• No direct demonstration that transport flux (versus protein presence) mediates the inflammatory and renal phenotypes