Ca²⁺ Binding Protein S100A1 Competes with Calmodulin and PIP2 for Binding Site on the C-Terminus of the TPRV1 Receptor

Abstract

Transient receptor potential vanilloid 1 ion channel (TRPV1) belongs to the TRP family of ion channels. These channels play a role in many important biological processes such as thermosensation and pain transduction. The TRPV1 channel was reported to be also involved in nociception. Ca(2+) ions are described to participate in the regulation of TRP channels through the interaction with Ca(2+)-binding proteins, such as calmodulin or S100A1. Calmodulin is involved in the Ca(2+)-dependent regulation of TRPV1 via its binding to the TRPV1 C-terminal region. However, the role of the Ca(2+)-binding protein S100A1 in the process of TRP channel regulation remains elusive. Here we characterized a region on the TRPV1 C-terminus responsible for the interaction with S100A1 using biochemical and biophysical tools. We found that this region overlaps with previously identified calmodulin and PIP2 binding sites and that S100A1 competes with calmodulin and PIP2 for this binding site. We identified several positively charged residues within this region, which have crucial impact on S100A1 binding, and we show that the reported S100A1-TRPV1 interaction is calcium-dependent. Taken together, our data suggest a mechanism for the mutual regulation of PIP2 and the Ca(2+)-binding proteins S100A1 and calmodulin to TRPV1.

Shared CaM‐ and S100A1‐binding epitopes in the distal TRPM4 N terminus

“…The dissociation constants of TRPM4np WT with CaM and S100A1 were in a comparable micromolar range for both complexes, which corresponds to the data of previous binding affinities measured for other TRP/CaM and TRP/S100A1 complexes [33,34,37]. Using steady-state fluorescence anisotropy measurements, we have determined the dissociation constants of the TRPM4np/CaM and TRPM4np/S100A1 complexes with clusters of hydrophobic L134, L138, V143 and basic R139, R140, R144 residues involved in the interactions.…”

“…Using steady-state fluorescence anisotropy measurements, we have determined the dissociation constants of the TRPM4np/CaM and TRPM4np/S100A1 complexes with clusters of hydrophobic L134, L138, V143 and basic R139, R140, R144 residues involved in the interactions. The Ca 2+ dependence of TRP/CaM or TRP/S100A1 interactions was validated in our previous experiments [33][34][35]37], which made it possible to use buffers with 2 mM of CaCl 2 in our binding assays. Using steadystate fluorescence anisotropy measurements, we determined the dissociation constants of the TRPM4np/ CaM and TRPM4np/S100A1 complexes.…”

“…CaM becomes more extended with each pair of EF-hands upon Ca 2+ binding, exposing a hydrophobic patch via CaM a-helix flexible linker that is available to interact with a target receptor domain [28]. This first step reveals the positive amino-acid residues eligible to form a specific interaction with the ligand [33][34][35][36][37][38][39][40]. Both monomer subunits are composed of four helices containing two EF-hand calcium-binding loops [29].…”

Control of cell mechanics by RhoA and calcium fluxes during epithelial scattering

“…31 High frequency calcium fluxes at the membrane result from increased channel opening events alone. TRP channel opening frequency is reportedly controlled by PIP2 [59][60][61][62] and inhibited by calmodulin. 59,[63][64][65] Studying these proteins in context of growth factor-stimulated calcium influx and EMT may be of interest.…”

“…TRP channel opening frequency is reportedly controlled by PIP2 [59][60][61][62] and inhibited by calmodulin. 59,[63][64][65] Studying these proteins in context of growth factor-stimulated calcium influx and EMT may be of interest. However, regulation by PIP2 or calmodulin does not explain why microtubule targeting agents inhibit high frequency calcium influxes following HGF stimulation.…”