Abstract
The molecular basis for divalent cationic permeability in transient receptor potential melastatin subtype (TRPM) channels is not fully understood. Here we studied the roles of all eight acidic residues, glutamate or aspartate, and also the glutamine residue between pore helix and selectivity filter in the pore of TRPM2 channel. Mutants with alanine substitution in each of the acidic residues, except Glu-960 and Asp-987, formed functional channels. These channels exhibited similar Ca2+ and Mg2+ permeability to wild type channel, with the exception of the E1022A mutant, which displayed increased Mg2+ permeability. More conservative E960Q, E960D, and D987N mutations also led to loss of function. The D987E mutant was functional and showed greater Ca2+ permeability along with concentration-dependent inhibition of Na+-carrying currents by Ca2+. Incorporation of negative charge in place of Gln-981 between the pore helix and selectivity filter by changing it to glutamate, which is present in the more Ca2+-permeable TRPM channels, substantially increased Ca2+ permeability. Expression of concatemers linking wild type and E960D mutant subunits resulted in functional channels that exhibited reduced Ca2+ permeability. These data taken together suggest that Glu-960, Gln-981, Asp-987, and Glu-1022 residues are engaged in determining divalent cationic permeation properties of the TRPM2 channel.
Highlights
The melastatin subtype of transient receptor potential (TRPM)6 ion channels is widely expressed in neuronal, cardiovascular, immune, and endothelial cells where they are engaged in diverse physiological and pathophysiological processes [1,2,3,4,5,6,7]
TRPM2 channels are activated by adenosine diphosphoribose (ADPR) and by oxidative stress and mediate immune function, insulin secretion, endothelial permeability, and cell death that are induced by oxidative stress (8 –14)
Currents for the E1022A mutant were significantly reduced when compared with wild type (WT) (Fig. 1C) despite normal surface expression shown by biotin-labeling analysis
Summary
The melastatin subtype of transient receptor potential (TRPM)6 ion channels is widely expressed in neuronal, cardiovascular, immune, and endothelial cells where they are engaged in diverse physiological and pathophysiological processes [1,2,3,4,5,6,7]. Accumulating evidence supports an important role of the ion selectivity filter in Ca2ϩ and Mg2ϩ permeation of TRPV and TRPM channels (15, 19 –26). The TRPM7 channel carrying the D1054A mutation is functional and has virtually the same pore properties as wild type (WT), including the Ca2ϩ and Mg2ϩ permeation [23].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
