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-β-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.

F-actin mediates motility both at the leading edge of a cell and in the nucleus.

Megakaryoblastic Leukemia 1 and 2 (MKL1/2) are transcriptional coactivators of Serum Response Factor (SRF) with an essential role for hepatocellular carcinoma (HCC) growth and oncogene-induced senescence. In this report, we identified myoferlin as a novel MKL/SRF target gene by gene expression profiling and verification in vivo in HCC xenografts. Myoferlin was overexpressed in human and murine HCCs triggered by conditional expression of constitutively active SRF-VP16 protein in hepatocytes. Furthermore, myoferlin was required for HCC cell invasion, proliferation and anchorage-independent cell growth. We provide evidence that myoferlin is a crucial gene target of MKL1/2 mediating its effect on oncogene-induced senescence by modulating the activation state of the EGFR and downstream MAPK and p16-/Rb pathways. Depletion of myoferlin in tumour cells from SRF-VP16-derived murine HCCs induced a senescence phenotype. These findings identify MKL1/2 and myoferlin as novel therapeutic targets to treat human HCC by a senescence-inducing strategy.

In the recent years, the role of actin and actin-binding proteins in gene transcription has received considerable attention. Nuclear monomeric and polymerized actin and several actin binding proteins have been detected in the mammalian cell nucleus, although their roles in transcription are just beginning to emerge. Our group recently reported that the actin-binding protein Filamin A interacts with the transcriptional coactivator MKL1 to link actin polymerization with transcriptional activity of Serum Response Factor. Here we summarize the regulation and function of MKL1, and highlight this novel mechanism of MKL1 regulation through binding to Filamin A and its implications for cell migration.