Stipes, E. J. | Search bioRxiv

bioRxiv2023

TRPM7-dependent electrical signals drive phagocytic clearance for effective anti-fungal defense

Sentinel phagocytes of the innate immune system have a critical role in detecting and eliminating fungal pathogens. We used patch clamp electrophysiology to explore the electrical signals elicited when macrophages engulf Candida albicans. In the perforated patch configuration, which is least disruptive to intracellular signaling, we detected a composite outwardly rectifying current during the engulfment of C. albicans or zymosan. FTY720, a known inhibitor of ion channel TRPM7, suppressed the current. We then tested the hypothesis that TRPM7 regulates the engulfment and clearance of C. albicans. We found that Trpm7-/- macrophages are highly deficient in the engulfment of C. albicans. Trpm7-/- macrophages initiate phagocytosis of yeast but are defective in sealing the phagocytic cups. While the precise mechanism through which TRPM7 regulates phagosome sealing is not clear, we tested the immunological significance of this discovery using a mouse model of systemic candidiasis. We show that in mice, wherein TRPM7 is deleted selectively in the myeloid cells, infection by C. albicans results in significantly higher lethality, increased colonization of vital organs and increased inflammatory cytokines in the blood. Our study establishes TRPM7 as an ion channel critical for the innate immune responses against fungal pathogens and sets the stage for cell biological studies that define the mechanisms through which TRPM7 regulates phagosome sealing. Significance statementThe worldwide increase in deadly or persistent fungal infections has prompted the research for alternative ways of treatment. We applied the specialized, perforated patch clamp technique to track and identify electrical currents elicited during the detection and engulfment of fungi by macrophages. The ion channel TRPM7 emerged as an important determinant of anti-fungal host defense as its deletion in the murine myeloid cells made the host mice highly susceptible to lethal candidiasis. Ion channels are attractive drug targets whose activation and inhibition can be manipulated with pharmacological therapeutics. This study raises the possibility of enhancing fungal clearance using activators of TRPM7. Such pharmacological strategy may benefit patients of persistent fungal infections that are recalcitrant to anti-fungal drugs.

immunology↗

bioRxiv2018

Targeting ion channel TRPM7 promotes the thymic development of Regulatory T cells by increasing IL-2-dependent STAT5 activation

In BriefGenetic deletion of Trpm7 in T-cells or pharmacological inhibition of TRPM7 channel promotes the development of fully functional Treg cells by increasing IL-2R and STAT5-dependent FOXP3 expression in the developing thymocytes. The study identifies the ion channel TRPM7 as a putative drug target to increase Treg numbers in vivo and induce immunotolerance.\n\nHIGHLIGHTSO_LIIon channel TRPM7 controls Treg development\nC_LIO_LIThe deletion of Trpm7 in the T-cell lineage increases fully functional Treg cells in the periphery\nC_LIO_LITRPM7 negatively regulates Foxp3 expression by restraining IL-2-dependent STAT5 activation\nC_LIO_LIInhibition of TRPM7 channel by FTY720 promotes the development of functional Treg cells\nC_LI\n\nSUMMARYThe thymic development of regulatory T cells (Treg), the crucial suppressors of the effector T cells (Teff), is governed by the transcription factor FOXP3. Despite the clinical significance of Treg cells, there is a dearth of druggable molecular targets capable of increasing Treg numbers in vivo. We report a surprising discovery that TRPM7 restrains Treg development by negatively regulating STAT5-dependent Foxp3 expression. The deletion of Trpm7 potentiates the thymic development of Treg cells, leads to a significantly higher frequency of functional Treg cells in the periphery and renders the mice highly resistant to T cell-dependent hepatitis. The deletion of Trpm7 or the inhibition of TRPM7 channel activity by the FDA-approved prodrug FTY720, increases IL-2 sensitivity through a feed forward positive feedback loop involving high IL-2R expression and STAT5 activation. Enhanced IL-2 signaling increases the expression of Foxp3 in thymocytes and promotes the development of Treg cells. Thus, TRPM7 emerges as the first ion channel that can be drugged to increase Treg numbers, revealing a novel pharmacological path toward the induction of immune tolerance.

immunology↗