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Aim: AMP‐activated protein kinase (AMPK) is activated during cellular energy perturbation. AMPK complexes are composed of three subunits and several variants of AMPK are expressed in skeletal muscle. The regulatory AMPKγ3 subunit is predominantly expressed in fast‐twitch muscle fibers. A human AMPKγ3 R225W mutation has been described. The mutation increases the total pool of AMPK activity in cells cultured from R225W carrier muscle and is associated with increased glycogen levels in mature skeletal muscle. This led to the idea of AMPKγ3 being involved in the regulation of skeletal muscle glycogen levels. Evidence for this causative link remains to be provided. Methods: We studied muscle biopsies from human carriers of the AMPKγ3 R225W mutation and we developed a novel AMPKγ3 R225W knock‐in mouse model (KI HOM). Through in vitro, in situ, and ex vivo techniques, we investigated AMPK activity, AMPK function, and glycogen levels in skeletal muscle of humans and mice. Results: In human carriers, the basal AMPKγ3‐associated activity was reduced when assayed in the absence of exogenous AMP. No difference was observed when assayed under AMP saturation, which was supported by findings in muscle of KI HOM mice. Furthermore, effects of AICAR/muscle contraction on AMPKγ3‐associated activity were absent in KI HOM muscle. Muscle glycogen levels were not affected by the mutation in human carriers or in KI HOM mice. Conclusions: The AMPKγ3 R225W mutation does not impact the AMPK‐associated activity in human skeletal muscle and the mutation is not linked to glycogen accumulation. The R225W mutation ablates the AMPKγ3‐associated activation by AICAR/muscle contractions, presumably due to loss of nucleotide binding in the CBS 1 domain of AMPKγ3. [ABSTRACT FROM AUTHOR]

Tumor progression and response to treatment are highly affected by interactions between cancer cells and the tumor microenvironment (TME). Many of the soluble factors and signaling receptors involved in this crosstalk are shed by a disintegrin and metalloproteinases (ADAMs). Upregulation of ADAM15 has been linked to worse survival in cancer patients and a tumor‐promoting function both in vitro and in murine cancer models. Although ADAM15 has been involved in cell‐cell and cell‐extracellular matrix interactions, its role in the crosstalk between cancer cells and the TME in vivo remains unexplored. Therefore, we aimed to understand how ADAM15 regulates the cell composition of the TME and how it affects tumor progression. Here, we showed an upregulation of ADAM15 in tumor tissues from rectal cancer patients. Subcutaneous injection of wildtype and ADAM15‐knockout CT26 colon cancer cells in syngeneic mice confirmed the protumorigenic role of ADAM15. Profiling of tumors revealed higher immune cell infiltration and cancer cell apoptosis in the ADAM15‐deficient tumors. Specifically, loss of ADAM15 led to a reduced number of granulocytes and higher infiltration of antigen‐presenting cells, including dendritic cells and macrophages, as well as more T cells. Using in vitro assays, we confirmed the regulatory effect of ADAM15 on macrophage migration and identified ADAM15‐derived CYR61 as a potential molecular mediator of this effect. Based on these findings, we speculate that targeting ADAM15 could increase the infiltration of immune cells in colorectal tumors, which is a prerequisite for effective immunotherapy. [ABSTRACT FROM AUTHOR]

Type I interferon (IFN-α/β) plays a critical role in suppressing viral replication by driving the transcription of hundreds of interferon-sensitive genes (ISGs). While many ISGs are transcriptionally activated by the ISGF3 complex, the significance of other signaling intermediates in IFN-α/β-mediated gene regulation remains elusive, particularly in rare cases of gene silencing. In human Th2 cells, IFN-α/β signaling suppressed IL5 and IL13 mRNA expression during recall responses to T-cell receptor (TCR) activation. This suppression occurred through a rapid reduction in the rate of nascent transcription, independent of de novo expression of ISGs. Further, IFN-α/β-mediated STAT4 activation was required for repressing the human IL5 gene, and disrupting STAT4 dimerization reversed this effect. This is the first demonstration of STAT4 acting as a transcriptional repressor in response to IFN-α/β signaling and highlights the unique activity of this cytokine to acutely block the expression of an inflammatory cytokine in human T cells. [ABSTRACT FROM AUTHOR]

Intensive microbial growth typically observed in laboratory rarely occurs in nature. Because of severe nutrient deficiency, natural populations exhibit near-zero growth ( NZG). There is a long-standing controversy about sustained NZG, specifically whether there is a minimum growth rate below which cells die or whether cells enter a non-growing maintenance state. Using chemostat with cell retention ( CCR) of P seudomonas putida, we resolve this controversy and show that under NZG conditions, bacteria differentiate into growing and VBNC (viable but not non-culturable) forms, the latter preserving measurable catabolic activity. The proliferating cells attained a steady state, their slow growth balanced by VBNC production. Proteomic analysis revealed upregulated (transporters, stress response, self-degrading enzymes and extracellular polymers) and downregulated (ribosomal, chemotactic and primary biosynthetic enzymes) proteins in the CCR versus batch culture. Based on these profiles, we identified intracellular processes associated with NZG and generated a mathematical model that simulated the observations. We conclude that NZG requires controlled partial self-digestion and deep reconfiguration of the metabolic machinery that results in the biosynthesis of new products and development of broad stress resistance. CCR allows efficient on-line control of NZG including VBNC production. A well-nuanced understanding of NZG is important to understand microbial processes in situ and for optimal design of environmental technologies. [ABSTRACT FROM AUTHOR]

The interaction between the T cell receptor (TCR) and its cognate antigen/major histocompatibility complex (MHC) complex activates a cascade of intracellular protein phosphorylations within the T cell. The signals are initiated by the specific phosphorylation of two tyrosine residues located in a conserved sequence motif termed an ITAM (immune receptor-based tyrosine activation motif). There are 10 ITAMs in the TCR complex, and 6 of these ITAMs are present in the TCRς homodimer. Following TCR stimulation, the TCRς subunit forms two tyrosinephosphorylated intermediates of 21- and 23-kDa, respectively. The dramatic and diverse biological responses of T cells are proposed to be partly regulated by the relative ratios of the 21- vs. 23-kDa phosphorylated forms of TCRς that are induced following TCR ligation. In this review, we describe a stepwise model of ς phosphorylation required for the formation of these two phosphorylated derivatives. We describe the kinases and phosphatases controlling these phosphorylation processes. In addition, we present some preliminary findings from ongoing studies that discuss the contributions of each phosphorylated form of ς on T cell development, TCR signaling, T cell energy induction, and T cell survival. [ABSTRACT FROM AUTHOR]