Dissection of the components for PIP ₂ activation and thermosensation in TRP channels

Abstract

Phosphatidylinositol 4,5-bisphosphate (PIP2) plays a central role in the activation of several transient receptor potential (TRP) channels. The role of PIP2 on temperature gating of thermoTRP channels has not been explored in detail, and the process of temperature activation is largely unexplained. In this work, we have exchanged different segments of the C-terminal region between coldsensitive (TRPM8) and heat-sensitive (TRPV1) channels, trying to understand the role of the segment in PIP2 and temperature activation. A chimera in which the proximal part of the C-terminal of TRPV1 replaces an equivalent section of TRPM8 C-terminal is activated by PIP2 and confers the phenotype of heat activation. PIP2, but not temperature sensitivity, disappears when positively charged residues contained in the exchanged region are neutralized. Shortening the exchanged segment to a length of 11 aa produces voltage-dependent and temperature-insensitive channels. Our findings suggest the existence of different activation domains for temperature, PIP2, and voltage. We provide an interpretation for channel-PIP2 interaction using a full-atom molecular model of TRPV1 and PIP2 docking analysis. chimera ͉ temperature activation ͉ C-terminal domain ͉ molecular model P hosphatidylinositol 4,5-bisphosphate (PIP 2 ) acts as a second messenger phospholipid and is the source of another three lipidic-derived messengers (DAG, IP 3 , PIP 3 ). Although the amount of PIP 2 in the membrane is very low, it is able to regulate the activity of ion channels transporters and enzymes (1-3). Several TRP channels reveal some degree of PIP 2 dependence. PIP 2 depletion inhibits TRPM7, TRPM5, TRPM8, TRPV5, and TRPM4 currents (4-9). In the case of TRPM8, some key positively charged residues present in a well conserved sequence contained in the C-terminal region of TRP channels, the TRP domain, were found to be crucial in determining the apparent affinity of PIP 2 activation (7). Residues K995, R998, and R1008 in the TRP box and TRP domain are critically involved in the activation of TRPM8 by PIP 2 . The hydrolysis of PIP 2 also constitutes an important mechanism for the Ca 2ϩ -dependent desensitization of TRPM8 (6, 7). Because of the high sequence similarity among TRP channels in the TRP domain region, it has been proposed that the family of TRP channels possesses a common PIP 2 -binding site located on its proximal C terminus (7, 10, 11). Different from its counterparts, TRPV1 shows a PLC/ NGF-dependent inhibition (12), where binding of NGF to trkA is coupled to PLC activation that leads to PIP 2 hydrolysis. Mutagenesis experiments suggested the presence of a PIP 2 -dependent inhibitory domain (13). In this model, the sensitization observed in TRPV1 is explained on the basis of PIP 2 hydrolysis as it acts as a tonical inhibitor. An alternative model has been proposed for the inhibition based on NGF-dependent phosphorylation of the TRPV1 C-terminal domain and a subsequent increase in membrane expression (14). These observations, together with the finding that...

The Transmembrane Segment S6 Determines Cation versus Anion Selectivity of TRPM2 and TRPM8

“…Finally, it has been suggested that the gating of TRPM8 is associated with a net loss of hydrophobic interactions within a putative temperature sensor domain (18). The same group has recently presented a molecular model of the TRPV1 channel that involves a direct interaction of the S5 and S6 domains with the channel activator PIP 2 (46). Such an idea might be used to explain why the M8-S6-Lys mutant displays larger currents at room temperature than wildtype TRPM8.…”

Direct Regulation of BK Channels by Phosphatidylinositol 4,5-Bisphosphate as a Novel Signaling Pathway

“…In particular, PIP 2 directly modulates the activity of ion channels and transporters ( Hilgemann and Ball, 1996 ;Fan and Makielski, 1997 ;Runnels et al, 2002 ;Roh á cs et al, 2003 ;Chemin et al, 2005 ;Suh and Hille 2005 ;Brauchi et al, 2007 ;Hilgemann, 2007 ;Roh á cs 2007 ;Voets and Nilius, 2007 ). In spite of the key roles of PIP 2 and BK channels in cell excitability and signaling, it remains unknown whether PIP 2 can directly modulate BK channel function.…”

Modular thermal sensors in temperature-gated transient receptor potential (TRP) channels

“…TRP channels have a membrane topology similar to voltage-gated K þ channels (12), albeit with relatively large intracellular termini (13). Both the pore domain (11,14,15) and the C terminus (16,17) have been implicated in temperature gating. For example, single residue mutations at the outer pore of TRPV3 abrogated its heat activation (14), whereas alterations of the pore turret compromised the gating of TRPV1 (15).…”