Role of the phagosomal redox-sensitive TRP channel TRPM2 in regulating bactericidal activity of macrophages

Abstract

Acidification of macrophage phagosomes serves an important bactericidal function. We show here that the redox-sensitive transient receptor potential (TRP) cation channel TRPM2 is expressed in the phagosomal membrane and regulates macrophage bactericidal activity through the activation of phagosomal acidification. Measurement of the TRPM2 current in phagosomes identified TRPM2 as a functional redox-sensitive cation channel localized in the phagosomal membrane. Simultaneous measurements of phagosomal Ca 2+ changes and phagosome acidification in macrophages undergoing phagocytosis demonstrated that TRPM2 was required to mediate the efflux of cations and for phagosomal acidification during the process of phagosome maturation. Acidification in phagosomes was significantly reduced in macrophages isolated from Trpm2 −/− mice as compared to wild type, and acidification was coupled to reduced bacterial clearance in Trpm2 −/− mice. Trpm2 +/+ macrophages treated with the vacuolar H + -ATPase inhibitor bafilomycin showed reduced bacterial clearance, similar to that in Trpm2 −/− macrophages. Direct activation of TRPM2 using adenosine diphosphate ribose (ADPR) induced both phagosomal acidification and bacterial killing. These data collectively demonstrate that TRPM2 regulates phagosomal acidification, and is essential for the bacterial killing function of macrophages.

Neutrophil Activation of Endothelial Cell-Expressed TRPM2 Mediates Transendothelial Neutrophil Migration and Vascular Injury

“…TRPM2, a.k.a TRPC7 and LTRPC-2, is a non-selective cation channel expressed in mammalian tissue, including endothelial cells, blood cells such as PMNs, bone marrow cells, brain, spleen, heart, liver, and lungs (5). Expression of TRPM2 in macrophages and PMNs is important in regulating the bactericidal activity of phagocytic cells and PMN migration in tissue (6, 7). The binding of the intracellular second messenger adenosine diphosphoribose (ADPR) or related molecules to the Nudix box sequence motif (NUDT9-H) in its carboxyl-terminal domain regulates the gating of TRPM2 channel after exposure to oxidants (8–10).…”

Integrative Physiology of Pneumonia

“…Upon pathogen recognition, AMs directly contribute to immune resistance through the ingestion and phagocytosis of microbes (244) (FIGURE 2). Transmem-brane transport of ions by CFTR, TRPC6, TRPM2, and other channels and pumps coordinately render the phagosome acidic and inhospitable to microbes (103,104,418). In addition, synthesis of reactive oxygen and nitrogen intermediates also contributes to alveolar macrophage killing of phagocytized microbes (176,199).…”

Revisiting the role of calcium in phagosome formation and maturation

“…). Additionally, some ligand‐gated TRP channels have been reported to localize to the phagosome, including TRPV2, TRPM2, and TRPML1; these could putatively function in phagosomal Ca 2+ efflux from phagosomes (Fig. A; reviewed in Refs.…”

“…The second major subset of Ca 2+ channels in the lysosome consists of members of the TRP family, namely TRPML1 and TRPM2 . These channels are present in phagosomes, presumably acquired via phago‐lysosomal fusion . Interestingly, TRPML1 and TPC2 are gated by the lysosome‐resident phosphoinositide PtdIns(3,5)P 2 , which must contribute to their regulation in the course of phagosome maturation .…”