Lysosomal Ion Channels Emerge as Hidden Drivers of Chronic Pain
A new review reveals how ion channels inside lysosomes regulate pain signaling, opening potential therapeutic targets for chronic pain conditions.
Summary
Lysosomes, the cell's recycling centers, contain specialized ion channels that do more than manage cellular waste—they actively participate in pain signaling. This 2025 review from Hebei University synthesizes evidence that lysosomal channels including P2X4, TRPM8, TRPA1, Tmem63A, and TRPMLs contribute to chronic pain through mechanisms such as trafficking to the plasma membrane, lysosomal exocytosis of ATP and neurotransmitters, and mechanosensory signaling in dorsal root ganglion (DRG) neurons. These findings reframe lysosomes from passive degradation organelles to active participants in neuropathic and chronic pain pathways, suggesting that targeting lysosomal ion channels could represent a novel therapeutic strategy.
Detailed Summary
Pain research has long focused on plasma membrane receptors and ion channels in sensory neurons, but emerging evidence points to an unexpected contributor: ion channels embedded in the membranes of lysosomes. This 2025 narrative review consolidates current findings on how lysosomal ion channels shape pain biology, particularly in dorsal root ganglion (DRG) neurons and spinal microglia.
Lysosomes maintain tightly regulated ion environments—including high calcium (~0.5 mM, roughly 5,000× cytoplasmic levels) and a low pH of 4–5—that are essential for degradation, autophagy, and exocytosis. Multiple calcium-permeable channels reside in lysosomal membranes, including TRPMLs (1–3), TRPA1, TRPM8, Tmem63A, and P2X4. Sodium channels (TPCs) and potassium channels (Lyso-BK) regulate lysosomal membrane potential, modulating ion flux broadly. Mechanosensitive channels including LRRC8, TRPML2, and Tmem63A respond to osmotic and mechanical stress at the lysosomal membrane.
The review presents specific mechanisms linking these channels to pain. P2X4, normally sequestered in lysosomes with low surface expression, traffics to the plasma membrane of spinal microglia following nerve injury—driven by CCL2 signaling—where it mediates BDNF release and neuropathic pain. Additionally, lysosomal P2X4 activation by HIV gp120-induced deacidification in Schwann cells promotes ATP exocytosis, elevating calcium and ROS in DRG neurons. TRPM8 is constitutively supplied from late endosomes/lysosomes (LEL) to the plasma membrane in DRG neurons, with lysosomal TRPM8 residing preferentially in less-acidic, plasma membrane–proximal vesicles. TRPA1 in DRG lysosomes may mediate vesicular neurotransmitter exocytosis. Tmem63A forms a mechanosensory channel in lysosomal membranes and its expression in DRG neurons contributes to mechanical hypersensitivity in chronic pain models. TRPMLs are implicated through ROS sensitivity (TRPML1), chemokine release (TRPML2), and re-expression after nerve injury (TRPML3).
Autophagy and lysosomal exocytosis represent the two primary functional axes connecting lysosomes to pain. Autophagy activation consistently reduces neuropathic pain behaviors in rodent models, while its inhibition worsens them—indicating a protective, pain-suppressing role. Conversely, lysosomal exocytosis of ATP from DRG neurons and Schwann cells appears to amplify pain signaling, with ATP colocalized with the lysosomal marker Lamp1 and released via exocytosis upon noxious stimulation or nerve injury.
Despite compelling evidence, the authors acknowledge that this field is in early stages. Most mechanistic data come from cell lines or rodent models, and direct causal evidence in human pain conditions remains sparse. The specific contributions of individual lysosomal channels versus coordinated channel networks are not yet established. Translational potential—while real—requires further validation in human tissue and disease-relevant models.
Key Findings
- Lysosomal P2X4 traffics to plasma membrane via CCL2 signaling in microglia, driving BDNF-mediated neuropathic pain.
- TRPM8 is constitutively supplied from late endosomes/lysosomes to DRG neuron plasma membranes, regulating cold hypersensitivity.
- Tmem63A acts as a lysosomal mechanosensory channel in DRG neurons and contributes to mechanical hypersensitivity in chronic pain models.
- Lysosomal exocytosis of ATP from DRG neurons and Schwann cells amplifies pain signaling after peripheral nerve injury.
- Autophagy, regulated by lysosomal calcium channels, consistently reduces neuropathic pain behaviors in rodent models.
Methodology
This is a narrative review synthesizing published experimental studies on lysosomal ion channel biology and pain. Evidence is drawn primarily from rodent models of neuropathic pain, in vitro cell line experiments, and selected human disease associations. No original experimental data were generated by the review authors.
Study Limitations
The review is narrative rather than systematic, introducing selection bias in the evidence presented. Most mechanistic findings derive from rodent models or overexpression systems, limiting direct translation to human pain conditions. The precise in vivo roles of individual lysosomal channels versus combined channel interactions remain unresolved.
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