The protease DDI2 regulates NRF1 activation in response to Cadmium toxicity

DNA-damage inducible 1 homolog 2 (DDI2) is a protease that activates the transcription factor NRF1. Cellular models have shown that this pathway contributes to cell-stress adaptation, for example, on proteasome inhibition. However, DDI2 physiological function is unknown. Ddi2 Knock-out (KO) mice were embryonic lethal. Therefore, we generated liver-specific Ddi2-KO animals and used comprehensive genetic analysis to identify the molecular pathways regulated by DDI2. Here, we demonstrate that DDI2 contributes to metallothionein (MT) expression in mouse and human hepatocytes at basal and upon cadmium (Cd) exposure. This transcriptional program is dependent on DDI2-mediated NRF1 proteolytic maturation. In contrast, NRF1 homolog NRF2 does not contribute to MT production. Mechanistically, we observed that Cd exposure inhibits proteasome activity, resulting in DDI2-mediated NRF1 proteolytic maturation. In line with these findings, DDI2 deficiency sensitizes cells to Cd toxicity. This study identifies a function for DDI2 that links proteasome homeostasis to heavy metal mediated toxicity.

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DDI2 is required for embryonic development

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DDI2 contributes to MT1 and MT2 expression

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Cadmium mediated proteasome inhibition activates DDI2 mediated NRF1 activity

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DDI2 contributes to cell survival on Cadmium-induced toxicity

Tumor-induced reshuffling of lipid composition on the endoplasmic reticulum membrane sustains macrophage survival and pro-tumorigenic activity

Tumor-associated macrophages (TAMs) display pro-tumorigenic phenotypes for supporting tumor progression in response to microenvironmental cues imposed by tumor and stromal cells. However, the underlying mechanisms by which tumor cells instruct TAM behavior remain elusive. Here, we uncover that tumor-cell-derived glucosylceramide stimulated unconventional endoplasmic reticulum (ER) stress responses by inducing reshuffling of lipid composition and saturation on the ER membrane in macrophages, which induced IRE1-mediated spliced XBP1 production and STAT3 activation. The cooperation of spliced XBP1 and STAT3 reinforced the pro-tumorigenic phenotype and expression of immunosuppressive genes. Ablation of XBP1 expression with genetic manipulation or ameliorating ER stress responses by facilitating LPCAT3-mediated incorporation of unsaturated lipids to the phosphatidylcholine hampered pro-tumorigenic phenotype and survival in TAMs. Together, we uncover the unexpected roles of tumor-cell-produced lipids that simultaneously orchestrate macrophage polarization and survival in tumors via induction of ER stress responses and reveal therapeutic targets for sustaining host antitumor immunity.

[Caries receptivity: a modern diagnostic protocol. II. The most important tests]

In this, the second part of the paper, the main clinical tests available today for carrying out early diagnosis of carioreceptivity are reviewed. On its own, measurement of the DMF-T index can classify an individual as carioactive or evaluate his "experience of caries", but it does non determine with any degree of certainty the probability of future caries. Measurement of stimulated salivary flow is important only when this is greatly reduced, as happens, for example, in xerostomy, but the finding of an almost normal flow is not on its own sufficient to make a diagnosis of carioreceptivity certain. Assessment of salivary pH is not a reliable parameter for the screening of carioreceptivity although it may be an indicator of diseases (e.g. diabetes) or bad habits (e.g. heavy smokers) in the patient in question. So examination with very sophisticated methods is of little importance. The buffer potential of saliva, assessed with a colorimetric test, is the most reliable parameter as it measures an important property of saliva at individual level: the capacity to protect from local acidity. Some studies seem to point to the validity of the combined evaluation of DMF, pH, salivary flow and buffer power of saliva in the prediction of caries at the level of groups of individual, but this has little or no validity in the screening of individual carioreceptive subjects. Specific microbiological cultures for cariogenic microorganisms are the most reliable tests for the diagnosis of carioreceptivity, particularly Dentocult for the search for Streptococcus mutans which is the most important factors in caries. The search for lactobacilli also identifies bad hygienic and dietary habits in the patients.