iTAP, a novel iRhom interactor, controls TNF secretion by policing the stability of iRhom/TACE

The apical inflammatory cytokine TNF regulates numerous important biological processes including inflammation and cell death, and drives inflammatory diseases. TNF secretion requires TACE (also called ADAM17), which cleaves TNF from its transmembrane tether. The trafficking of TACE to the cell surface, and stimulation of its proteolytic activity, depends on membrane proteins, called iRhoms. To delineate how the TNF/TACE/iRhom axis is regulated, we performed an immunoprecipitation/mass spectrometry screen to identify iRhom-binding proteins. This identified a novel protein, that we name iTAP (iRhom Tail-Associated Protein) that binds to iRhoms, enhancing the cell surface stability of iRhoms and TACE, preventing their degradation in lysosomes. Depleting iTAP in primary human macrophages profoundly impaired TNF production and tissues from iTAP KO mice exhibit a pronounced depletion in active TACE levels. Our work identifies iTAP as a physiological regulator of TNF signalling and a novel target for the control of inflammation.info:eu-repo/semantics/publishedVersio

The Apoptosome Pathway to Caspase Activation in Primary Human Neutrophils Exhibits Dramatically Reduced Requirements for Cytochrome c

Caspase activation is a central event in numerous forms of apoptosis and results in the proteolytic degradation of multiple substrate proteins that contribute to the apoptotic phenotype. An important route to caspase activation proceeds via assembly of the “apoptosome” as a result of the cell stress–associated release of mitochondrial cytochrome c. Previous studies have shown that primary neutrophils are largely incapable of mitochondrial respiration, suggesting that these cells either lack functional mitochondria or possess a defective respiratory chain. This prompted us to examine whether neutrophils retain an intact cytochrome c/apoptotic protease-activating factor 1 (Apaf-1) pathway to caspase activation and apoptosis. We show that primary human neutrophils contain barely detectable levels of cytochrome c as well as other mitochondrial proteins. Surprisingly, neutrophil cell–free extracts readily supported Apaf-1–dependent caspase activation, suggesting that these cells may assemble cytochrome c–independent apoptosomes. However, further analysis revealed that the trace amount of cytochrome c present in neutrophils is both necessary and sufficient for Apaf-1–dependent caspase activation in these cells. Thus, neutrophils have a lowered threshold requirement for cytochrome c in the Apaf-1–dependent cell death pathway. These observations suggest that neutrophils retain cytochrome c for the purpose of assembling functional apoptosomes rather than for oxidative phosphorylation

Have the log-population processes stationary and independent increments? Empirical evidence for Italy, Spain and the USA along more than a century.

We review the classical Gibrat’s process for the population of city sizes. In particular, we are interested in whether the log-population process has stationary and independent (Gibrat’s Law for cities) increments. We have tested these characteristics for the case of the municipalities of Italy and Spain and the places of USA for a time span of more than one century. The results are clear: stationarity and independence are empirically rejected by standard tests. These results open theoretically the way for the observance of other city size distributions other than the lognormal and the double Pareto lognormal, something that in fact has already happened in the literature

Semaphorin 4B is an ADAM17-cleaved adipokine that inhibits adipocyte differentiation and thermogenesis

Objective: The metalloprotease ADAM17 (also called TACE) plays fundamental roles in homeostasis by shedding key signaling molecules from the cell surface. Although its importance for the immune system and epithelial tissues is well-documented, little is known about the role of ADAM17 in metabolic homeostasis. The purpose of this study was to determine the impact of ADAM17 expression, specifically in adipose tissues, on metabolic homeostasis.Methods: We used histopathology, molecular, proteomic, transcriptomic, in vivo integrative physiological and ex vivo biochemical approaches to determine the impact of adipose tissue-specific deletion of ADAM17 upon adipocyte and whole organism metabolic physiology.Results: ADAM17adipoq-creD/D mice exhibited a hypermetabolic phenotype characterized by elevated energy consumption and increased levels of adipocyte thermogenic gene expression. On a high fat diet, these mice were more thermogenic, while exhibiting elevated expression levels of genes associated with lipid oxidation and lipolysis. This hypermetabolic phenotype protected mutant mice from obesogenic challenge, limiting weight gain, hepatosteatosis and insulin resistance. Activation of beta-adrenoceptors by the neurotransmitter norepinephrine, a key regulator of adipocyte physiology, triggered the shedding of ADAM17 substrates, and regulated ADAM17 expression at the mRNA and protein levels, hence identifying a functional connection between thermogenic licensing and the regulation of ADAM17. Proteomic studies identified Semaphorin 4B (SEMA4B), as a novel ADAM17-shed adipokine, whose expression is regulated by physiological thermogenic cues, that acts to inhibit adipocyte differentiation and dampen thermogenic responses in adipocytes. Transcriptomic data showed that cleaved SEMA4B acts in an autocrine manner in brown adipocytes to repress the expression of genes involved in adipogenesis, thermogenesis, and lipid uptake, storage and catabolism.Conclusions: Our findings identify a novel ADAM17-dependent axis, regulated by beta-adrenoceptors and mediated by the ADAM17-cleaved form of SEMA4B, that modulates energy balance in adipocytes by inhibiting adipocyte differentiation, thermogenesis and lipid catabolism.(c) 2023 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Proteomic and functional analysis identifies galectin-1 as a novel regulatory component of the cytotoxic granule machinery

Secretory granules released by cytotoxic T lymphocytes (CTLs) are powerful weapons against intracellular microbes and tumor cells. Despite significant progress, there is still limited information on the molecular mechanisms implicated in target-driven degranulation, effector cell survival and composition and structure of the lytic granules. Here, using a proteomic approach we identified a panel of putative cytotoxic granule proteins, including some already known granule constituents and novel proteins that contribute to regulate the CTL lytic machinery. Particularly, we identified galectin-1 (Gal1), an endogenous immune regulatory lectin, as an integral component of the secretory granule machinery and unveil the unexpected function of this lectin in regulating CTL killing activity. Mechanistic studies revealed the ability of Gal1 to control the non-secretory lytic pathway by influencing Fas–Fas ligand interactions. This study offers new insights on the composition of the cytotoxic granule machinery, highlighting the dynamic cross talk between secretory and non-secretory pathways in controlling CTL lytic function

Deletion of iRhom2 protects against diet-inducedobesity by increasing thermogenesis

Objective:Obesity is the result of positive energy balance. It can be caused by excessive energy consumption but also by decreased energydissipation, which occurs under several conditions including when the development or activation of brown adipose tissue (BAT) is impaired. Herewe evaluated whether iRhom2, the essential cofactor for the Tumour Necrosis Factor (TNF) sheddase ADAM17/TACE, plays a role in thepathophysiology of metabolic syndrome.Methods:We challenged WT versus iRhom2 KO mice to positive energy balance by chronic exposure to a high fat diet and then compared theirmetabolic phenotypes. We also carried outex vivoassays with primary and immortalized mouse brown adipocytes to establish the autonomy ofthe effect of loss of iRhom2 on thermogenesis and respiration.Results:Deletion of iRhom2 protected mice from weight gain, dyslipidemia, adipose tissue inflammation, and hepatic steatosis and improvedinsulin sensitivity when challenged by a high fat diet. Crucially, the loss of iRhom2 promotes thermogenesis via BAT activation and beigeadipocyte recruitment, enabling iRhom2 KO mice to dissipate excess energy more efficiently than WT animals. This effect on enhanced ther-mogenesis is cell-autonomous in brown adipocytes as iRhom2 KOs exhibit elevated UCP1 levels and increased mitochondrial proton leak.Conclusion:Our data suggest that iRhom2 is a negative regulator of thermogenesis and plays a role in the control of adipose tissue homeostasisduring metabolic diseaseWellcome Trust strategic award (100574/Z/12/Z) and MRC MDU (MC_UU_12012/

An investigation of the role of caspase-9-interacting proteins in the molecular control of apoptosis

THESIS 6186Apoptosis is an important homeostatic mechanism that multicellular organisms utilize to delete cells during development and on an ongoing basis in the adult. At the molecular level, this requires the activation of a family of proteolytic enzymes called caspases. Caspases are constitutively present in healthy cells as inactive zymogens (procaspases). In cells stimulated to die, caspases become activated via proteolytic cleavage, mediated by other active caspases. Evidence suggests that because inactive caspases possess a basal level of proteolytic activity, enforced aggregation can stimulate their activation. Through the proteolysis of strategic cellular substrates, active caspases mediate the biochemical and phenotypical changes required during apoptosis

Systemic and cellular metabolism: the cause of and remedy for disease?

The word ‘metabolism’ is derived from the Greek word μεταβολή (metabolē), denoting ‘change’. True to this definition, it is now appreciated that a cell or tissue cannot change its behaviour without altering its metabolism. Hence, most key cell decision-making processes are tightly coupled to metabolic change. Conversely, perturbations in metabolite abundance or flux can alter cellular (and whole-body) function profoundly, giving rise to disease. This Special Issue on Systemic and Cellular Metabolism and Disease provides an integrative perspective on the importance of metabolism for health and disease alike. Spanning several orders of scale (from metabolites, proteins, organelles, organs/tissues and whole-body physiology), these review articles cover a breadth of topics, including the importance of metabolites as signalling regulators, metabolic disease, immunity, organelle function/dysfunction, ageing and neurodegenerative disease. One of the emergent themes is that just as metabolism is the fulcrum of biology, metabolic perturbances underpin most forms of acute, chronic, infectious and non-infectious human disease; ageing and senescence could be similarly viewed. Arguably most diseases are metabolic diseases; hence, modulating metabolism may help to ‘change’ disease outcomes