Effects of the Membrane Protein σ2/TMEM97 on P2RX3-Dependent Calcium Responses in Sensory Neurons: Implications for Pain

Introduction: The Sigma-2 receptor/TMEM97 (σ2/TMEM97) is a transmembrane protein located in the endoplasmic reticulum (ER) and plasma membrane, known for its role in modulating calcium signaling. Previous studies have shown that loss of σ2/TMEM97 is linked to prolonged inflammatory pain-like responses, although the underlying mechanisms remain unclear. Altered calcium signaling is a critical component in pain perception and transmission. The P2X purinoceptor 3 (P2RX3) is highly expressed in mechanical pain-sensing neurons and plays a crucial role in nociception associated with inflammation through calcium homeostasis, similar to σ2/TMEM97. This study investigated the potential interaction between σ2/TMEM97 and P2RX3 in modulating sensory neuron excitability during inflammation. Objective: To investigate the interaction between σ2/TMEM97 and P2RX3 in calcium signaling during pain, focusing on these receptors’ role in modulating sensory neuron excitability and pain response during inflammation. Materials and Methods: Primary dorsal root ganglion (DRG) cells were extracted from GCamp/NesCre/σ2/TMEM97 wildtype (WT) and knockout (KO) mice. DRGs were enzymatically dissociated and cultured in Hank’s Balanced Salt Solution (HBSS) supplemented with 10 mM HEPES, 10% fetal bovine serum (FBS), 1% penicillin-streptomycin, and 2% B-27 supplement. The cells were plated onto poly-D-lysine-coated coverslips. After 24 hours, calcium transients from GCaMP calcium binding were measured with CellSens software. Cells were perfused with a HEPES-buffered saline recording solution, and fluorescence changes in response to ATP (10, 25, and 50 µM) were recorded. Statistical analysis using Graph pad-prism was used to compare calcium responses between WT and KO cells. Results: At 10, 25, and 50 μM of ATP, WT cells did not exhibit significant fluorescence changes. However, in KO cells, while 10 and 25 μM of ATP showed no significant change, a significant increase in fluorescence was observed at 50 μM of ATP. Conclusions: The study indicates that σ2/TMEM97 likely modulates signaling through purinergic receptor-mediated calcium signaling, potentially via its interaction with P2RX3-dependent calcium homeostasis in sensory neurons. We acknowledge funding from American Physiological Society (ZSH), the Anson Clark Program (BAJ), NIH grant F31NS129269 (VMH), R01DK115478 (BJK) and R61NS127271 (BJK). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.