TRPM7 Channel Activity in Jurkat T Lymphocytes During Magnesium Depletion and Loading: Implications for Divalent Metal Entry and Cytotoxicity

Authors

Alayna Mellott
Jananie Rockwood
Tetyana Zhelay
Charles Tuan Luu
Taku Kaitsuka
J. Ashot Kozak, Wright State University - Main CampusFollow

Document Type

Article

Publication Date

9-22-2020

Abstract

TRPM7 is a cation channel-protein kinase highly expressed in T lymphocytes and other immune cells. It has been proposed to constitute a cellular entry pathway for Mg ²⁺ and divalent metal cations such as Ca ²⁺ , Zn ²⁺ , Cd ²⁺ , Mn ²⁺ , and Ni ²⁺ . TRPM7 channels are inhibited by cytosolic Mg ²⁺ , rendering them largely inactive in intact cells. The dependence of channel activity on extracellular Mg ²⁺ is less well studied. Here, we measured native TRPM7 channel activity in Jurkat T cells maintained in external Mg ²⁺ concentrations varying between 400 nM and 1.4 mM for 1-3 days, obtaining an IC ₅₀ value of 54 μM. Maintaining the cells in 400 nM or 8 μM [Mg ²⁺ ] _o resulted in almost complete activation of TRPM7 in intact cells, due to cytosolic Mg ²⁺ depletion. A total of 1.4 mM [Mg ²⁺ ] _o was sufficient to fully eliminate the basal current. Submillimolar concentrations of amiloride prevented cellular Mg ²⁺ depletion but not loading. We investigated whether the cytotoxicity of TRPM7 permeant metal ions Ni ²⁺ , Zn ²⁺ , Cd ²⁺ , Co ²⁺ , Mn ²⁺ , Sr ²⁺ , and Ba ²⁺ requires TRPM7 channel activity. Mg ²⁺ loading modestly reduced cytotoxicity of Zn ²⁺ , Co ²⁺ , Ni ²⁺ , and Mn ²⁺ but not of Cd ²⁺ . Channel blocker NS8593 reduced Co ²⁺ and Mn ²⁺ but not Cd ²⁺ or Zn ²⁺ cytotoxicity and interfered with Mg ²⁺ loading as evaluated by TRPM7 channel basal activity. Ba ²⁺ and Sr ²⁺ were neither detectably toxic nor permeant through the plasma membrane. These results indicate that in Jurkat T cells, entry of toxic divalent metal cations primarily occurs through pathways distinct from TRPM7. By contrast, we found evidence that Mg ²⁺ entry requires TRPM7 channels.

Repository Citation

Mellott, A., Rockwood, J., Zhelay, T., Luu, C. T., Kaitsuka, T., & Kozak, J. A. (2020). TRPM7 Channel Activity in Jurkat T Lymphocytes During Magnesium Depletion and Loading: Implications for Divalent Metal Entry and Cytotoxicity. Pflugers Archiv : European journal of physiology, 472 (11), 1589-1606.
https://corescholar.libraries.wright.edu/ncbp/1195

DOI

10.1007/s00424-020-02457-3