Adenine Nucleotide Translocase: From Nucleotide Carrier to a Modulator of Mitochondrial Bioenergetics, Quality Control, and Cellular Communication
Cytokine signaling is a major interface through which inflammatory cues are translated into mitochondrial functional changes. ANT isoforms represent key mitochondrial targets within this axis, converting cytokine-driven transcriptional and post-translational signals into changes in bioenergetics, redox balance, and permeability control.
Pro-inflammatory cytokines—including TNFα, IL-6, IL-1β, and interferons—consistently suppress ANT1 expression, largely via NF-κB–dependent transcriptional repression (Table 1) [11,100]. Functionally, this is associated with reduced ATP production, ΔΨm destabilization, increased ROS formation, and enhanced susceptibility to necrotic cell death. In this setting, inflammatory signaling acts upstream of ANT1 to lower mitochondrial stress tolerance thresholds.
Anti-inflammatory and immune-modulatory cytokines can exert opposing effects. IL-4 induces ANT1 in cardiomyocytes and ANT3 in T cells through kinase- and NF-κB-linked pathways and promotes cell survival programs [119]. IFN-γ regulates ANT3 via STAT1 signaling, with IL-4/STAT6 activity acting antagonistically [23,119]. These patterns indicate context-dependent, isoform-biased cytokine control rather than uniform regulation across ANT family members.
TGF-β signaling adds a further isoform-divergent layer. In senescent cells, TGF-β represses ANT2 transcription via NF1/Smad4 promoter complexes, increasing ROS and apoptosis susceptibility [120]. In contrast, elevated ANT1 levels in cardiomyocytes are associated with preserved ΔΨm and reduced TGF-β-linked apoptotic signaling, together with altered downstream SMAD responses [121]. These findings support differential integration of TGF-β signaling across ANT isoforms.
ANT also acts in the reverse direction by controlling mitochondrial danger signaling toward innate immune pathways. Reduced ANT1 function or destabilized ANT-dependent membrane control promotes release of mitochondrial danger-associated molecular patterns that activate the NLRP3 inflammasome. The tyrosine phosphatase SHP2 provides a counter-regulatory feedback mechanism: upon inflammasome activation, SHP2 translocates to mitochondria, associates with ANT1, and dephosphorylates it, stabilizing ΔΨm and limiting ROS and mtDNA release (Figure 5) [122]. This ANT1–SHP2 axis forms a negative feedback loop that restrains excessive inflammasome activation.
Recent data link ANT1 to cGAS–STING activating mtDNA release and ANT-dependent permeability control to innate immune polarization. Limiting ANT1 activity reduces mtDNA leakage and inflammatory signaling, extending ANT function to mitochondrial DAMP regulation [123].
Viewed in aggregate, cytokine networks do not merely regulate ANT but use ANT-dependent mitochondrial responses as an amplification or braking module within inflammatory signaling circuits. While cytokine-dependent regulation and inflammasome control illustrate how ANT-dependent mitochondrial dysfunction is converted into inflammatory signaling, mitochondrial RNA export represents a more direct route by which mitochondrial stress is exposed to cytosolic innate immune sensors, as described in Section 6.4.
Beyond mtDNA release, mitochondrial RNA has emerged as an ANT2-linked danger signal, although the precise transport mechanism and structural basis remain under active investigation. Recent studies suggest that ANT2 may participate in stress-associated mitochondrial RNA export, including double-stranded RNA (dsRNA), into the cytosol (Figure 6) [124,125]. This process is stress-responsive and associated with changes in membrane potential and ANT2 modification state, and appears mechanistically distinct from passive leakage during permeability transition.
Exported mtRNA activates cytosolic RNA sensors such as RIG-I and MDA5 and triggers type I interferon programs, linking mitochondrial dysfunction to innate immune signaling. In epithelial and immune cells, ANT2-dependent mtRNA export contributes to sustained interferon responses under conditions of metabolic or inflammatory stress.
A defined in vivo example is provided in allergic airway inflammation [126]. The transcription factor ETS2 is upregulated in airway epithelium and directly induces ANT2 expression. Increased ANT2 levels enhance cytosolic accumulation of mitochondrial RNA and dsRNA and amplify downstream cytokine responses. These pro-inflammatory effects are lost in ANT2-deficient models, supporting ANT2-dependent mtRNA export as a causal contributor linking mitochondrial stress to epithelial immune activation.
ANT2-mediated RNA export operates alongside other mitochondrial nucleic acid release routes—including defective PNPT1/SUV3-dependent RNA degradation, BAX/BAK macropores, VDAC oligomerization, and mitochondria-derived vesicles—and is functionally connected to permeability and quality-control pathways [127,128,129]. Together, these observations support a role for ANT2 in regulating mitochondrial RNA release during stress. Thereby, it links bioenergetic dysfunction to cytosolic RNA sensing and interferon responses. More broadly, these pathways intersect with immunometabolic programs, indicating that ANT-dependent stress signaling extends beyond epithelial and inflammatory responses to the metabolic specialization of immune cells, as discussed in Section 6.5.
ANT’s immunological relevance is evident in immune cell metabolism. In T cells, ANT2 functions as an immunometabolic checkpoint. T cell–specific deletion of ANT2 uncouples activation from classical oxidative phosphorylation requirements, limits ATP synthase activity and NAD+ regeneration, yet paradoxically enhances proliferation and effector function [130]. ANT2-deficient T cells increase mitochondrial biogenesis and exhibit improved antitumor immunity in vivo.
In macrophages, ANT1 supports oxidative metabolism, mitophagy, and polarization toward an anti-inflammatory M2 phenotype. In M2-polarized macrophages, CD147 translocates to mitochondria and interacts with ANT1, enhancing PINK1/Parkin-dependent mitophagy and respiratory chain integrity [131]. Disruption of this axis impairs mitophagy, attenuates M2 polarization, and reduces pathological airway remodeling. Recent in vivo and cell-based data support the role of ANT1-dependent mitochondrial regulation in macrophage polarization within ischemic tissue [100]. Cardiac ANT1 overexpression is associated with reduced pro-inflammatory cytokine expression, decreased M1 prevalence, and increased M2 macrophage infiltration, together with preserved mitochondrial integrity and lower oxidative stress.
Complementary data indicate an isoform- and context-dependent pattern. In metabolically stressed adipose tissue macrophages, free fatty acids promote ANT2-linked mitochondrial stress signaling via mPTP-associated ROS with downstream HIF-1α and NF-κB activation, whereas myeloid ANT2 deficiency reduces monocyte recruitment and pro-inflammatory macrophage activation and improves systemic insulin sensitivity and glucose tolerance [132]. Thus, ANT1-associated mitochondrial stabilization tends to favor anti-inflammatory polarization, while ANT2-dependent stress signaling in metabolically challenged myeloid cells supports pro-inflammatory programs.
ANT1-dependent effects also extend beyond immune cells. Cardiomyocyte-specific ANT1 overexpression generates a protective secretome enriched in VEGF and HSP27, which improves mitochondrial function, suppresses apoptosis, and promotes anti-inflammatory macrophage responses in surrounding tissue [100]. Together, these findings establish ANT as a central immunometabolic regulator that integrates mitochondrial energy exchange with immune activation, polarization, and tissue–immune crosstalk. Once ANT-dependent mitochondrial states are linked to intracellular signaling and immune cell behavior, the next conceptual step is to consider how these signals extend beyond the individual cell. ANT-associated mechanisms at the plasma membrane and in extracellular vesicles suggest that mitochondrial state information can also be communicated at the tissue level.
ANT-dependent mitochondrial information can also be transmitted beyond the cell to shape tissue-level and intercellular communication. A growing body of evidence demonstrates that ANT can operate outside its canonical mitochondrial context, either through ectopic localization at the plasma membrane or via incorporation into extracellular vesicles. In these settings, ANT enables the controlled export of energetic and stress-related signals, allowing mitochondrial function to influence neighboring cells and the tissue microenvironment.
Although ANT was originally defined as an inner mitochondrial membrane carrier, multiple studies report ectopic ANT localization at the plasma membrane in diverse mammalian cell types, including fibroblasts, hepatocytes, cancer cells, and neurons [133,134,135,136]. Surface biotinylation, antibody accessibility, and membrane fractionation approaches support that this pool is not solely due to mitochondrial contamination. In these settings, ANT contributes to extracellular nucleotide handling and local energy-dependent signaling.
At the cell surface, ANT has been linked to ATP-dependent control of migration and matrix remodeling. In tumor cells, plasma membrane-associated ANT2 interacts with MT1-MMP and is proposed to support pericellular proteolysis and invasion [135]. In developing neurons, surface-localized ANT1 and ANT2 participate in SRC family kinase-dependent signaling downstream of adhesion molecules, promoting transient ATP release and activity-dependent neurite growth [136].
In metabolic and vascular contexts, plasma membrane-associated ANT contributes to extracellular nucleotide balance and receptor-linked transport processes. In hepatocytes, ANT associates with ecto-F1-ATPase–containing complexes involved in HDL uptake, and pharmacological ANT modulation alters extracellular ADP/ATP ratios and lipoprotein internalization [134]. In human bronchial epithelial cells, ANT supports airway hydration and preserves ciliary beating following exposure to environmental stressors such as cigarette smoke, thereby sustaining mucociliary clearance [137]. Finally, in erythrocytes, ANT forms supramolecular complexes with VDAC and TSPO2 that support regulated ATP release and purinergic vascular signaling [138].
Ectopic ANT localization is also observed in intracellular pathogens, where ANT homologs mediate host-derived ATP uptake and extracellular nucleotide sensing, supporting pathogen survival under energy-limited conditions [139].
In sum, ectopic ANT localization extends nucleotide carrier function into the extracellular signaling space, where it contributes to purinergic control and energy-dependent cell–environment interactions.
ANT also contributes to intercellular communication through incorporation into extracellular vesicles (EVs), particularly exosomes derived from multivesicular bodies. EVs transfer proteins, lipids, and nucleic acids between cells and thereby propagate metabolic and stress signals. Proteomic studies have detected ANT isoforms, including ANT1, ANT2, and ANT3, in EVs from cancer cells, immune cells, and stressed tissues [140,141,142]. These vesicles are distinct from mitochondria-derived vesicles (MDVs), which bud directly from mitochondria and selectively package mitochondrial components [143].
ANT-containing EVs have been proposed to convey aspects of mitochondrial functional state to recipient cells. Secretomes enriched in EVs from ANT1-overexpressing cardiomyocytes enhance survival of ischemic cardiomyocytes and endothelial cells and reduce pro-inflammatory activation in macrophages, demonstrating paracrine transfer of ANT-linked mitochondrial adaptation [100].
Conversely, EV-mediated delivery of ANT-modifying factors can influence ANT-dependent functions in recipient cells. For example, exosomal transfer of the deacetylase SIRT2 promotes deacetylation of ANT1/2 and enhances ATP production in axons [144]. EV-associated ANT and ANT-modifying factors therefore represent a vesicle-based extension of mitochondrial regulation, enabling ANT-dependent metabolic and permeability states to influence neighboring cells.
Across the mechanisms discussed here, ANT emerges as a remarkably versatile mitochondrial protein. Its functions as a nucleotide, fatty acid, and dsRNA transporter, as well as a regulator, organizer, and signal sender and receiver, enabling it to influence a broad range of intracellular and extracellular processes (Figure 7). In this framework, ANT links these functions to bioenergetic control, quality maintenance, and cellular communication by modulating permeability transition sensitivity, protein import dynamics, and mitochondrial stress signaling. Through these activities, ANT helps determine whether mitochondrial perturbations are buffered, redirected into repair pathways, or propagated as adaptive or inflammatory signals.
The strength of mechanistic support varies across these domains. While nucleotide exchange and permeability regulation are firmly established, roles in mitochondrial RNA signaling, import complex interactions, and intercellular communication remain less structurally defined. In many systems, isoforms have not been examined in parallel, limiting definitive conclusions regarding intrinsic isoform specialization. At the same time, the available evidence indicates that ANT isoforms are not merely interchangeable carriers, but are deployed in distinct physiological and stress-responsive contexts, with overlapping yet biased functions across tissues and disease settings. A detailed process-oriented summary of these isoform-associated functional contexts is provided in Supplementary Table S1.
Functionally, ANT operates within feedback-organized signaling circuits: upstream kinase and cytokine pathways regulate ANT activity, whereas ANT-dependent changes in membrane potential, redox balance, and nucleic acid exposure feed back into cytosolic and nuclear programs. Because ANT integrates essential bioenergetic exchange with stress signaling control, future therapeutic strategies will likely require selective modulation of regulatory interactions and response thresholds rather than global transport inhibition.
Framing ANT as a modulator of mitochondrial bioenergetics, quality control, and cellular communication provides a coherent model that reconciles established carrier functions with emerging signaling roles while explicitly acknowledging current mechanistic limitations.