Calpain cleaves the carboxyl terminus of TRPV1 and modulates receptor tachyphylaxis

Abstract

Transient receptor potential vanilloid-1 (TRPV1) plays a critical role in noxious heat sensation and pain hypersensitivity development in chronic pain. Sustained or repeated exposure to capsaicin, a classic TRPV1 agonist, induces TRPV1 desensitization. This partially accounts for the analgesic effect of capsaicin. However, the regulatory mechanisms of TRPV1 desensitization remain poorly understood. In this study, we found that capsaicin acts on TRPV1 to induce the activation of calpain, a Ca2+-sensitive cysteine protease, in a manner unrelated to cellular injury. Calpain cleaves rTRPV1 at the carboxyl terminus of G819/S820. Lack of the distal carboxyl terminus leads to reduced TRPV1 localization on the plasma membrane, potentially due to increased receptor internalization and impaired subunit assembly. This finding was corroborated by whole-cell patch clamp recordings. Additionally, the {Delta}820-838 mutant of rTRPV1 shows resistance to tachyphylaxis as induced by repetitive capsaicin stimulation. This study reveals a pivotal role for calpain in TRPV1 desensitization where its activation constrains TRPV1 channel function while simultaneously increasing its resistance to tachyphylaxis, thereby acting to maintain TRPV1 activity within an appropriate range.