Significance: Transient receptor potential melastatin type 2 (TRPM2) is an oxidative stress-sensing calcium-permeable channel that is thought to contribute to the calcium influx associated with neurodegenerative diseases. Here we show that TRPM2 deficiency lowers chronic unpredictable stress (CUS)-induced reactive oxygen species (ROS) and calpain activation and prevents aberrant hyperactivation of cyclin-dependent kinase 5 (Cdk5). In mice models of CUS, genetic elimination of TRPM2 normalized behavioral deficits. Moreover, removal of Cdk5 reversed the antidepressant-like behaviors observed in Trpm2 ^−/− mice. Our results reveal the important roles of TRPM2 in raising ROS levels and aberrantly hyperactivating Cdk5 in mouse models of CUS and suggest that TRPM2 could be a target for treating ROS-induced neurodegenerative diseases such as depression.

Background: We have previously reported that histamine-induced pruritus was attenuated in toll-like receptor 4 (TLR4) knockout mice due to decreased transient receptor potential V1 (TRPV1) sensitivity. Our results implied that TLR4 potentiated TRPV1 activation in sensory neurons; however, the molecular mechanism has yet to be elucidated. In this study, we investigated the molecular mechanisms of TLR4-mediated TRPV1 potentiation using TLR4-deficient sensory neurons and a heterologous expression system. Methods: Primary sensory neurons were obtained from wild-type or TLR4 knockout mice, and HEK293T cells expressing TRPV1 and TLR4 were prepared by transient transfection. TRPV1 activity was analyzed by calcium imaging, fluorophotometry, and patch-clamp recording. Subcellular protein distribution was tested by immunocytochemistry and cell surface biotinylation assay. Protein interaction was assessed by western blot and immunoprecipitation assay. Results: Direct association between TRPV1 and TLR4 was detected in HEK293T cells upon heterologous TRPV1 and TLR4 expression. In an immunoprecipitation assay using TLR4-deletion mutants and soluble toll/interleukin-1 receptor (TIR) protein, the cytoplasmic TIR domain of TLR4 was required for TLR4-TRPV1 association and TRPV1 potentiation. In TLR4-deficient sensory neurons, the activation-induced desensitization of TRPV1 increased, accompanied by enhanced TRPV1 clearance from the cell membrane upon activation compared to wild-type neurons. In addition, heterologous TLR4 expression inhibited activation-induced TRPV1 endocytosis and lysosomal degradation in HEK293T cells. Conclusion: Our data show that direct association between TRPV1 and TLR4 through the TIR domain enhances TRPV1 activity by blocking activation-induced TRPV1 desensitization.