EXPRESS: RIN1 inhibited TRPV1-dependent pain sensitization in a mouse model of bone cancer pain

The Ras and Rab interactor 1 (RIN1) is a multifunctional signaling protein that has been implicated in the regulation of tumor cell migration and proliferation. Here we found that RIN1 was abundant in the dorsal root ganglia (DRG) neurons positive for transient receptor potential vanilloid 1 (TRPV1), a critical mediator of pain sensitization in patients with metastatic bone cancer. Our data showed that RIN1 interacted with TRPV1 and induced the endocytosis of TRPV1 through its guanine nucleotide exchange factor activity toward small GTPase Rab5. This process limited the duration and magnitude of TRPV1-dependent acute pain responses in intact male mice. Conditioned knockout of RIN1 in the DRG neurons enhanced TRPV1 activity and led to the reflexive nociceptive sensitization and aversive pain behaviors. In mice with the bone cancer pain, we found a significant reduction of RIN1 protein level in the DRG neurons, which correlated with TRPV1 accumulation on the plasma membrane. Special rescue of RIN1 expression in the DRG neurons repressed the surface TRPV1 distribution and alleviated both the reflexive-defensive and affective-motivational aspects of bone cancer pain. Our data thus revealed an important role of RIN1 in the negative control over TRPV1-dependent pain behaviors.