Alternative Splicing of the NMDA Receptor Subunit GluN1 Mediated by Polypyrimidine Tract‐Binding Protein Dimerization in the Trigeminal Ganglion Contributes to Orofacial Allodynia

Orofacial neuropathic pain, a debilitating condition associated with trigeminal nerve injury, is often characterized by allodynia. N ‐methyl‐ d ‐aspartate receptors (NMDARs), particularly the GluN1 subunit, play a central role in mediating this pain. The GluN1 subunit undergoes alternative splicing at exon 5, generating isoforms GluN1a (lacking the exon 5‐encoded N1 cassette) and GluN1b (retaining the N1 cassette), which have distinct functional roles. However, the contribution of GluN1 exon 5 splicing and the mechanisms governing this process in orofacial neuropathic pain are not fully understood. This study investigates the role of GluN1 exon 5 splicing in the development of orofacial allodynia utilizing a mouse model of chronic constriction injury of the infraorbital nerve (CCI‐ION). We found that CCI‐ION induces enhanced exon 5 splicing in the trigeminal ganglion (TG), promoting the expression of GluN1a and contributing to orofacial allodynia. A key regulator of this splicing event is the polypyrimidine tract‐binding protein (PTB), which binds to GluN1 pre‐mRNA in a manner dependent on PTB dimerization. We also identified protein disulfide isomerase 3 (PDIA3) as a modulator of PTB dimerization. PDIA3 regulates the formation of PTB dimers in the nucleus, which drives GluN1 exon 5 splicing and the development of orofacial allodynia. These findings reveal a PDIA3‐PTB‐GluN1 axis that regulates alternative splicing of GluN1 exon 5 in response to trigeminal nerve injury, providing new insights into the molecular mechanisms underlying orofacial neuropathic pain and potential therapeutic targets for its treatment.