Zinc Inactivates Melastatin Transient Receptor Potential 2 Channels via the Outer Pore

Abstract

Zinc ion (Zn 2؉ ) is an endogenous allosteric modulator that regulates the activity of a wide variety of ion channels in a reversible and concentration-dependent fashion. Here we used patch clamp recording to study the effects of Zn 2؉ on the melastatin transient receptor potential 2 (TRPM2) channel. Zn 2؉ inhibited the human (h) TRPM2 channel currents, and the steady-state inhibition was largely not reversed upon washout and concentration-independent in the range of 30 -1000 M, suggesting that Zn 2؉ induces channel inactivation. Zn 2؉ inactivated the channels fully when they conducted inward currents, but only by half when they passed outward currents, indicating profound influence of the permeant ion on Zn 2؉ inactivation. Alanine substitution scanning mutagenesis of 20 Zn 2؉ -interacting candidate residues in the outer pore region of the hTRPM2 channel showed that mutation of Lys 952 in the extracellular end of the fifth transmembrane segment and Asp 1002 in the large turret strongly attenuated or abolished Zn 2؉ inactivation, and mutation of several other residues dramatically changed the inactivation kinetics. The mouse (m) TRPM2 channels were also inactivated by Zn 2؉ , but the kinetics were remarkably slower. Reciprocal mutation of His 995 in the hTRPM2 channel and the equivalent Gln 992 in the mTRPM2 channel completely swapped the kinetics, but no such opposing effects resulted from exchanging another pair of species-specific residues, Arg 961 / Ser 958 . We conclude from these results that Zn 2؉ inactivates the TRPM2 channels and that residues in the outer pore are critical determinants of the inactivation.

TRPM2-mediated intracellular Zn2+ release triggers pancreatic β-cell death

“…Since extracellular Ca 2 + entry potentiates ROS-induced Zn 2 + release and Ca 2 + is an activator of TRPM2 channels [32,33], we propose that extracellular Ca 2 + enters through the plasma membrane TRPM2 channels and co-stimulates (together with H 2 O 2 ) lysosomal TRPM2 channels to promote Zn 2 + release ( Figure 4E). Although TRPM2-channel-mediated Zn 2 + influx could be demonstrated in HEK-293 cells using FluoZin-3 [19], our attempts to demonstrate Zn 2 + permeation by electrophysiology have been unsuccessful [46], largely because concentration of Zn 2 + required to demonstrate Zn 2 + currents were found to inhibit the channel profoundly.…”

Reciprocal regulation of actin cytoskeleton remodelling and cell migration by Ca2+ and Zn2+: role of TRPM2 channels

“…Whether Zn 2+ plays a similar role in cell migration induced by other migration-promoting signals, and in the migration of other cell types, remains to be investigated. Furthermore, although a role for the TRPM2 channel, and for Zn 2+ , are clear, and H 2 O 2 -induced elevation of cytoplasmic Zn 2+ could be demonstrated using fluorescent probes, it has proved difficult to demonstrate permeability of the channel to Zn 2+ by electrophysiology (Manna et al, 2015;Yang et al, 2011). Thus, mechanisms other than direct Zn 2+ permeation by the channel cannot be excluded.…”

Extracellular Zinc Ion Regulates Transient Receptor Potential Melastatin 5 (TRPM5) Channel Activation through Its Interaction with a Pore Loop Domain

“…For example, TRPA1 is activated by about 20 M ZnCl 2 , and TRPM1 is inhibited by high concentrations (mM) of ZnCl 2 (18,19). TRPM2 is inactivated by more than 30 M ZnCl 2 , and Zn 2ϩ entering cells through TRPM7 channel is involved in Zn 2ϩ -mediated neuronal injury (20,21). In this study, we found extracellular Zn 2ϩ to be a potential blocker of TRPM5 activity.…”