Exploring a peripheral PIP₂-binding site and its role in the alternative regulation of the TRP channel superfamily

Phosphatidylinositol 4,5-bisphosphate (PIP₂) is recognized as an essential modulator of transient receptor potential (TRP) channels. Specifically, it influences the vanilloid receptor I (TRPV1), a pain receptor activated by a wide range of stimuli, including the binding of phospholipids, such as PIP₂. The primary PIP₂-binding site in TRPV1 has been identified through advanced techniques, revealing that the PIP₂ binds to a specific pocket composed of positively charged residues located predominantly within the proximal C-terminus region. Additionally, a conserved segment with positively charged amino acids, K431 and R432, situated at the beginning of TRPV1’s S1 transmembrane domain, has attracted considerable attention from the TRP research community. To date, our knowledge of this site’s function and the subsequent effects following PIP₂ binding is still emerging. In this work, MD simulations were conducted using coarse-grained models to investigate the binding dynamics of PIP₂ on both WT and various mutated forms of TRPV1 channels. Our findings indicate that the K431A and R432A mutations significantly reduce the frequency of PIP₂ contacts, suggesting that these mutated residues are part of a “peripheral binding pocket.” This pocket seems to play a crucial role in facilitating the entry of PIP₂ to the TRPV1 channel’s primary binding site. Furthermore, our research has shown that these highly conserved residues within the TRPV subfamily are also structurally conserved across other TRP subfamilies, such as TRPM and TRPC, a detail not evident from sequence alignment alone. Consequently, we propose the existence of a structurally conserved peripheral PIP₂-binding site shared among the diverse members of the TRP family, which can be categorized into distinct subfamilies.