Project description:TRPM7 (transient receptor potential cation channel subfamily M member 7) is a chanzyme with channel and kinase domains essential for embryo development. Using gamete-specific Trpm7-null lines, we report that TRPM7-mediated Mg2+ influx is indispensable for reaching the blastocyst stage. TRPM7 was expressed dynamically from gametes to blastocysts, displaying stage-specific and distinct localizations on the plasma membrane, cytoplasm, and nucleus, and undergoes cleavage that produces C- terminal kinase fragments. TRPM7 underpinned Mg2+ homeostasis throughout this time, and excess Mg2+ but not Zn2+ or Ca2+ overcame the arrest of Trpm7-null embryos; expressing Trpm7 mRNA restored development, but mutant versions failed or were less effective. Transcriptomic analyses of embryos lacking Trpm7 revealed an abundance of oxidative stress-pathway genes, confirmed by mitochondrial dysfunction, and a reduction of transcription factor networks essential for proliferation; Mg2+ supplementation corrected these defects. Hence, TRPM7 underpins Mg2+ homeostasis in preimplantation embryos, prevents oxidative stress, and promotes gene expression patterns necessary for developmental progression and cell lineage specification.
Project description:MANUSCRIPT ABSTRACT: The most abundant cellular divalent cations, Mg2+ (mM) and Ca2+ (nM-µM), antagonistically regulate divergent metabolic pathways with several orders of magnitude affinity preference, but its physiological significance of this competition remains largely unknown. In mice consuming a Western diet, genetic ablation of the mitochondrial Mg2+ channel Mrs2 prevents weight gain, enhances mitochondrial activity, decreases fat accumulation in the liver, and causes prominent browning of white adipose. Mrs2 deficiency further restrains citrate efflux from the mitochondria, making it unavailable to support de novo lipogenesis. As citrate is an endogenous Mg2+ chelator, this may represent an adaptive response to a perceived deficit of the cation. Transcriptional profiling of liver and white adipose reveals higher expression of genes involved in glycolysis, b-oxidation, thermogenesis, and HIF-1a-targets, in Mrs2-/- mice that are further enhanced under Western diet-associated metabolic stress. Thus, lowering mMg2+ is sufficient to promote metabolism and dampens diet induced obesity and metabolic syndrome.
Project description:Improve the reliability of the phosphosite occupancy determined by the third method by comparison of the ratio of absolute occupancy and relative occupancy from HCC samples. An outlier score was introduced to evaluate the deviation between ratio of absolute occupancy and relative occupancy and further to balance the confidence interval and deviation instead of set a fixed threshold.
Project description:In response to low levels of magnesium (Mg2+), the PhoQP two component system induces the transcription of two convergent genes, one encoding a 31-amino acid protein denoted MgtS and the second encoding a small, regulatory RNA (sRNA) denoted MgrR. Previous studies showed that the MgtS protein interacts with and stabilizes the MgtA Mg2+ importer to increase intracellular Mg2+ levels, while the MgrR sRNA base pairs with the eptB mRNA thus affecting lipopolysaccharide modification. Surprisingly, we found overexpression of the MgtS protein also leads to induction of the PhoRB regulon. Studies to understand this activation showed that MgtS forms a complex with a second protein, PitA, a cation-phosphate symporter. Given that the additive effect of ∆mgtA and ∆mgtS mutations on intracellular Mg2+ concentrations seen previously is lost in the ∆pitA mutant, we suggest that MgtS binds to and blocks Mg2+ leakage through PitA under Mg2+-limiting conditions. Consistent with a detrimental role of PitA in low Mg2+, we also observe MgrR sRNA repression of PitA synthesis. Thus, PhoQP induces the expression of two convergent small genes in response to Mg2+ limitation whose products both repress PitA activity and levels to increase intracellular Mg2+ levels. Funded by NIH Intramural Program ZIA HD008855-11.