Direct modulation of TRPM4 and TRPM3 channels by the phospholipase C inhibitor U73122.

Michael G Leitner, Niklas Michel, Marc Behrendt, Marlen Dierich, Sandeep Dembla, Bettina U Wilke, Maik Konrad, Moritz Lindner, Johannes Oberwinkler, Dominik Oliver

Br. J. Pharmacol., 2016 Jun 21 , ,

Signalling through phospholipase C (PLC) controls many cellular processes. Much information on the relevance of this important pathway has been derived from pharmacological inhibition of the enzymatic activity of PLC. We find that the most frequently employed PLC inhibitor, U73122, activates endogenous ionic currents in widely used cell lines. Given the extensive use of U73122 in research, we set out to identify the U73122-sensitive ion channels.We performed detailed biophysical analysis of the U73122-induced currents in frequently used cell lines.We find that at concentrations required to inhibit PLC U73122 modulates the activity of transient receptor potential melastatin (TRPM) channels through covalent modification. U73122 is a potent agonist of ubiquitously expressed TRPM4 channels that activates endogenous TRPM4 in Chinese hamster ovary (CHO) cells with an EC50 of approximately 440 nM independently of PLC and of the downstream second messengers PI(4,5)P2 and Ca(2+) . U73122 also potentiates Ca(2+) -dependent TRPM4 currents in human Jurkat T-cells, endogenous TRPM4 in HEK293T cells, and recombinant human TRPM4. In contrast to TRPM4, TRPM3 channels are inhibited whereas the closely related TRPM5 channels are insensitive to U73122, showing that U73122 exhibits high specificity within the TRPM channel family.Given the wide spread expression of TRPM4 and TRPM3 channels, these actions of U73122 must be considered when interpreting its effects on cell function. U73122 may also be useful to identify and characterise TRPM channels in native tissue thus facilitating the analysis of their physiology.