Towards Purification of human TRPV1 Pore Domain

The transient receptor potential channel subfamily V member 1 (TRPV1) functions as the heat and capsaicin receptor. It can be activated by heat, protons, pungent chemicals, and a variety of other endogenous mediators of nociception. TRPV1 is a non-selective cation channel consisting of 6 transmembrane domains (S1-S6), with helices S1-S4 forming the sensing domain and the S5-S6 helices forming the pore domain. Understanding the TRPV1 channel is imperative due to its relation to a variety of human diseases, including cancer, type II diabetes, hyper and hypothermia, and inflammatory disorders of the airways and bladder. Although TRPV1 is the best-studied thermosensitive-TRP channels of all the 28 family members, the molecular underpinning and the contributions of the human TRPV1 pore domain in thermo-sensing remains elusive. Recently, the human TRPV1 sensing domain was found to contribute to heat activation. It was found to undergo a non-denaturing temperature-dependent conformational change. This finding triggered interest in studying the function and the role of the human TRPV1 pore domain in the heat activation process. Specifically, to identify whether heat activation is intrinsic to the pore domain. This thesis paper explores and optimizes the purification protocol of the human TRPV1 pore domain through three different methods. The first method was using a denaturant, the second method was increasing the length of the histidine tags through Q5 insertion, and the third method was incorporating the protein construct into nanodiscs. In addition to the above three methods, size exclusion chromatography and ion-exchange chromatography were utilized after thrombin cleavage to separate the human TRPV1 pore domain from the cleaved MBP deca-histidine tags as well as the impurities.