SUMOylation of Kir7.1 participates in neuropathic pain through regulating its membrane expression in spinal cord neurons

Aims Potassium (K+) channels have been demonstrated to play a prominent involvement in nociceptive processing. Kir7.1, the newest members of the Kir channel family, has not been extensively studied in the CNS, and its function remains largely unknown. The present study investigated the role of spinal Kir7.1 in the development of pathological pain. Methods and Results Neuropathic pain was induced by spared nerve injury (SNI). The mechanical sensitivity was assessed by von Frey test. Immunofluorescence staining assay revealed that Kir7.1 was predominantly expressed in spinal neurons but not astrocytes or microglia in normal rats. Western blot results showed that SNI markedly decreased the total and membrane expression of Kir7.1 in the spinal dorsal horn accompanied by mechanical hypersensitivity. Blocking Kir7.1 with the specific antagonist ML418 or knockdown kir7.1 by siRNA led to mechanical allodynia. Co-IP results showed that the spinal kir7.1 channels were decorated by SUMO-1 but not SUMO-2/3, and Kir7.1 SUMOylation was upregulated following SNI. Moreover, inhibited SUMOylation by GA (E1 inhibitor) or 2-D08 (UBC9 inhibitor) can increase the spinal surface Kir7.1 expression. Conclusion SUMOylation of the Kir7.1 in the spinal cord might contribute to the development of SNI-induced mechanical allodynia by decreasing the Kir7.1 surface expression in rats.