ABSTRACT
Cyclooxygenase-2 (COX-2) is a key regulator of inflammation. High constitutive COX-2 expression enhances survival and proliferation of cancer cells, and adversely impacts antitumor immunity. The expression of COX-2 is modulated by various signaling pathways. Recently, we identified the melastatin-like transient-receptor-potential-7 (TRPM7) channel-kinase as modulator of immune homeostasis. TRPM7 protein is essential for leukocyte proliferation and differentiation, and upregulated in several cancers. It comprises of a cation channel and an atypical α-kinase, linked to inflammatory cell signals and associated with hallmarks of tumor progression. A role in leukemia has not been established, and signaling pathways are yet to be deciphered. We show that inhibiting TRPM7 channel-kinase in chronic myeloid leukemia (CML) cells results in reduced constitutive COX-2 expression. By utilizing a CML-derived cell line, HAP1, harboring CRISPR/Cas9-mediated TRPM7 knockout, or a point mutation inactivating TRPM7 kinase, we could link this to reduced activation of AKT serine/threonine kinase and mothers against decapentaplegic homolog 2 (SMAD2). We identified AKT as a direct in vitro substrate of TRPM7 kinase. Pharmacologic blockade of TRPM7 in wildtype HAP1 cells confirmed the effect on COX-2 via altered AKT signaling. Addition of an AKT activator on TRPM7 kinase-dead cells reconstituted the wildtype phenotype. Inhibition of TRPM7 resulted in reduced phosphorylation of AKT and diminished COX-2 expression in peripheral blood mononuclear cells derived from CML patients, and reduced proliferation in patient-derived CD34+ cells. These results highlight a role of TRPM7 kinase in AKT-driven COX-2 expression and suggest a beneficial potential of TRPM7 blockade in COX-2-related inflammation and malignancy.
Subject(s)
Leukemia, Myelogenous, Chronic, BCR-ABL Positive , Leukemia, Myeloid , TRPM Cation Channels , Humans , Proto-Oncogene Proteins c-akt/genetics , Cyclooxygenase 2/genetics , TRPM Cation Channels/genetics , Leukocytes, Mononuclear/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Inflammation , Protein Serine-Threonine Kinases/geneticsABSTRACT
The melastatin-like transient-receptor-potential-7 protein (TRPM7), harbouring a cation channel and a serine/threonine kinase, has been implicated in thymopoiesis and cytokine expression. Here we show, by analysing TRPM7 kinase-dead mutant (Trpm7 R/R ) mice, that the enzymatic activity of the receptor is not essential for thymopoiesis, but is required for CD103 transcription and gut-homing of intra-epithelial lymphocytes. Defective T cell gut colonization reduces MHCII expression in intestinal epithelial cells. Mechanistically, TRPM7 kinase activity controls TGF-ß-induced CD103 expression and pro-inflammatory T helper 17, but not regulatory T, cell differentiation by modulating SMAD2. Notably, we find that the TRPM7 kinase activity promotes gut colonization by alloreactive T cells in acute graft-versus-host disease. Thus, our results unravel a function of TRPM7 kinase in T cell activity and suggest a therapeutic potential of kinase inhibitors in averting acute graft-versus-host disease.
Subject(s)
Graft vs Host Disease/genetics , Intestines/immunology , Lymphopoiesis/genetics , T-Lymphocytes, Regulatory/cytology , TRPM Cation Channels/genetics , Th17 Cells/cytology , Animals , Antigens, CD/immunology , Cell Differentiation/genetics , Genes, MHC Class II/genetics , Genes, MHC Class II/immunology , Graft vs Host Disease/immunology , Integrin alpha Chains/immunology , Mice , Mutation , Smad2 Protein/immunology , T-Lymphocytes/cytology , T-Lymphocytes/immunology , T-Lymphocytes, Regulatory/immunology , TRPM Cation Channels/immunology , Th17 Cells/immunology , Transforming Growth Factor beta/immunologyABSTRACT
The immune system protects our body against foreign pathogens. However, if it overshoots or turns against itself, pro-inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, or diabetes develop. Ions, the most basic signaling molecules, shape intracellular signaling cascades resulting in immune cell activation and subsequent immune responses. Mutations in ion channels required for calcium signaling result in human immunodeficiencies and highlight those ion channels as valued targets for therapies against pro-inflammatory diseases. Signaling pathways regulated by melastatin-like transient receptor potential (TRPM) cation channels also play crucial roles in calcium signaling and leukocyte physiology, affecting phagocytosis, degranulation, chemokine and cytokine expression, chemotaxis and invasion, as well as lymphocyte development and proliferation. Therefore, this review discusses their regulation, possible interactions and whether they can be exploited as targets for therapeutic approaches to pro-inflammatory diseases.
