Gating modulation by heat of the polycystin transient receptor potential channel PKD2L1 (TRPP3)

Abstract

Polycystic kidney disease 2-like 1 (PKD2L1), previously called transient receptor potential polycystin 3 (TRPP3), forms a voltage-dependent nonselective cation channel that exhibits large tail currents triggered by repolarization after depolarization. Since it has previously been proposed that temperature sensitivity of some TRP channels is linked to the voltage-dependent gating, we here investigated heating effects on PKD2L1 currents in human embryonic kidney HEK293T cells overexpressing mouse PKD2L1. Tail PKD2L1 currents were increased by heating to 32 °C, but decreased at more than 36 °C. Voltage dependency of the PKD2L1 channel was shifted by heating in a bimodal fashion: an increase in temperature to 32 °C and to 36 °C shifted the activation curves toward the left and the right, respectively. In addition, heating accelerated deactivation of tail PKD2L1 currents. To analyze the channel gating kinetics, single-channel events of the PKD2L1 channel were recorded at hyperpolarized potentials under whole-cell configurations. A rise in temperature decreased the open probability of the channel. Dwell-time analysis showed that both open and closed dwell times during heating were shorter than those at room temperature. Interestingly, a rapid temperature drop after heating markedly enhanced the PKD2L1 currents at both single-channel and whole-cell levels. The rebound activation of the PKD2L1 channel was due to an increase in the open probability but not in the single-channel conductance. These results suggest that heating opens but subsequently inactivates PKD2L1 channels, which is essential for the rebound activation of the channel after heating.

The asparagine 533 residue in the outer pore loop region of the mouse PKD2L1 channel is essential for its voltage‐dependent inactivation

“…We next examined the temperature sensitivity of the PKD2L1 channel. As previously reported [6], although heating to 40°C increased and decreased a single-channel conductance and channel activity (NPo) of the WT channels, respectively (data not shown), rapid decrease in the temperature induced an obvious activation of the WT channels (Fig. 5A).…”

Opening TRPP2 ( PKD2L1 ) requires the transfer of gating charges

“…Thus, we conducted single-channel recordings and observed an increase in the unitary single-channel conductance (163 to 209 pS), consistent with reports using the mouse ortholog of TRPP2 (SI Appendix, Fig. S6D) (40). Since ion conductance is a property of the channel pore and not the voltage sensor, we tested if the TRPP2 channel can be gated independently of a functioning voltage sensor.…”

“…Besides osmotic membrane swell, heat is another stimulus that polymodally potentiates polycystin channel currents. Currents carried by homomeric TRPP2 and heteromeric TRPP2+PKD1-L1 channels are potentiated by heat when expressed in the cilium (temperature coefficient Q 10 = 8) and plasma membranes (Q 10 = 6) (24,40). We wondered if heat might alter TRPP2 voltage-dependent gating as a mechanism for the observed effect.…”

A proton current associated with sour taste: distribution and functional properties

“…More recently, careful biophysical experiments have shown that PK32L1, also known as TRPP3, can form homomeric channels; these channels are activated by high voltages, giving rise to large tail currents measured on repolarization (30). Homomeric PKD32L1 channels are sensitive to temperature (31), and osmotic pressure (30) and show a bimodal sensitivity to pH (32). PKD2L1 has also been proposed to mediate calcium entry into the primary cilium, where it regulates developmental patterning (33).…”