Signal-sustained imaging of mitophagy with an Enzyme-Activatable Metabolic Lipid-Labeling Probe.

Imaging of mitophagy is of significance as aberrant mitophagy is engaged in multiple diseases. Mitophagy has been imaged with synthetic or biotic pH sensors by reporting pH acidification en route delivery into lysosomes. To circumvent uncertainty of acidity-dependent signals, we herein report an enzyme-activatable probe covalently attached on mitochondrial inner membrane (ECAM) for signal-persist mitophagy imaging. ECAM is operated via ΔΨm-driven accumulation of Mito-proGreen in mitochondria and covalent linking of the trapped probe with azidophospholipids metabolically incorporated into the mitochondrial inner membrane. Upon mitophagy, ECAM is delivered into lysosomes and hydrolyzed by LNPEP/leucyl aminopeptidase, yielding turn-on green fluorescence that is immune to lysosomal acidity changes and stably retained in fixed cells. With ECAM, phorbol-12-myristate-13-acetate (PMA) was identified as a highly potent inducer of mitophagy. Overcoming signal susceptibility of pH probes and liability of ΔΨm probes to dissipation from stressed mitochondria, ECAM offers an attractive tool to study mitophagy and mitophagy-inducing therapeutic agents.

Pirin Inhibits FAS-Mediated Apoptosis to Support Colorectal Cancer Survival.

Resistance to immunotherapy in colorectal cancer (CRC) is associated with obstruction of FAS (Apo-1 or CD95)-dependent apoptosis, a hallmark of cancer. Here it is demonstrated that the upregulation of pirin (PIR) protein in colon cancers promotes tumorigenesis. Knockout or inhibition of PIR dramatically increases FAS expression, FAS-dependent apoptosis and attenuates colorectal tumor formation in mice. Specifically, NFκB2 is a direct transcriptional activator of FAS and robustly suppressed by PIR in dual mechanisms. One is the disruption of NFκB2 complex (p52-RELB) association with FAS promoter, the other is the inhibition of NIK-mediated NFκB2 activation and nuclear translocation, leading to the inability of active NFκB2 complex toward the transcription of FAS. Furthermore, PIR interacts with FAS and recruits it in cytosol, preventing its membrane translocation and assembling. Importantly, knockdown or knockout of PIR dramatically sensitizes cells to FAS mAb- or active CD8+ T cells-triggered cell death. Taken together, a PIR-NIK-NFκB2-FAS survival pathway is established, which plays a key role in supporting CRC survival.

Impact of exercise training on gut microbiome imbalance in obese individuals: a study based on Mendelian randomization analysis.

Objective: The aim of this study was to investigate the relationship between exercise and gut Microbiome and to assess its possible causality. Methods: Using Mendelian randomization (MR) research methods, we collected genetic data from different populations, including genetic variants associated with relative abundance or presence of microbial taxa as instrumental variables. At the same time, we extracted results related to obesity and gut Microbiome from existing relevant studies and used inverse variance weighting (IVW), weighted median, and MR-Egger regression to assess the causal relationship between obesity and gut Microbiome. We plotted forest plots and scatter plots of the association between obesity and gut Microbiome. Results: Gut Microbiome was positively associated with obesity, and four bacterial genera (Akkermansia, RuminococcaceaeUCG011, Holdemania, and Intestinimonas) were associated with obesity according to inverse variance-weighted estimation in at least one MR method. Inverse variance weighted estimation showed that obesity was associated with obesity in Akkermansia (OR = 0.810, 95% CI 0.608-1.079, p = 0.04), RuminococcaceaeUCG011 (OR = 1.238, 95% CI 0. 511-2.999, p = 0.04), Holdemania Intestinimonas (OR = 1.214, 95% CI 1.002-1.470, p = 0.03), and Intestinimonas (OR = 0.747, 95% CI 0.514-1.086, p = 0.01) had a relevant effect. Obesity decreased the abundance of Akkermansia, Intestinimonas microbiome and increased the abundance of RuminococcaceaeUCG011, Holdemania microbiome. Conclusion: The results of this study, conducted using a two-sample Mendelian randomization method, suggest a causal relationship between obesity and intestinal microbiome. Obesity decreased the abundance of Akkermansia, Intestinimonas microbiome and increased the abundance of RuminococcaceaeUCG011, Holdemania microbiome. More randomized controlled trials are necessary to elucidate the protective effects of exercise on gut Microbiome and its unique protective mechanisms.

Imaging of Mitophagy Enabled by an Acidity-Reporting Probe Anchored on the Mitochondrial Inner Membrane.

Classical chemical probes are prone to dissipation from stressed organelles, as evidenced by the incapability of mitochondrial dyes to image mitophagy linked to multiple diseases. We herein reported mitophagy imaging via covalent anchoring of a lysosomal probe to the mitochondrial inner membrane (CALM). Utilizing DBCORC-TPP, an azide-conjugatable probe with acidity-triggered fluorescence, CALM is operated via ΔΨm-promoted probe accumulation in mitochondria and thereby bioorthogonal ligation of the trapped probe with azido-choline (Azcholine) metabolically installed on the mitochondrial membrane. Overcoming the limitation of synthetic probes to dissipate from stressed organelles, CALM enables signal-on fluorescence imaging of mitophagy induced by starvation and is further employed to reveal mitophagy in ferroptosis. These results suggest the potential of CALM as a new tool to study mitophagy.

Installation of high-affinity Siglec-1 ligand on tumor surface for macrophage-engaged tumor suppression.

Siglecs that binds cell surface sialoglycans are a family of immunomodulatory receptors, of which, Siglec-7 expressed on natural killer (NK) cells promotes tumor immunoevation while the role of Siglec-1 expressed on macrophages on tumor development remains largely unexplored. Herein, we selectively introduced high affinity sialoside ligands of Siglec-1 and Siglec-7 to tumor cell surface via in vivo Strain-promoted Azide-Alkyne cyclization of TCCSiaα2,3-Lactose or FITCSiaα2,6-Lactose with 9-azido sialic acid (AzSia) metabolically installed on tumor cell surface. We found that TCCSiaα2,3-Lactose conjugated on tumor surface moderately inhibited tumor growth while FITCSiaα2,6-Lactose promote tumor growth. These results suggest high-affinity ligand of Siglec-1 dispalyed on tumors surface provide a new perspective for tumor immunotherapy.

c-Src facilitates tumorigenesis by phosphorylating and activating G6PD.

Glucose-6-phosphate dehydrogenase (G6PD) is the first and rate-limiting enzyme in pentose phosphate pathway (PPP), excessive activation of which has been considered to be involved in tumorigenesis. Here, we show that tyrosine kinase c-Src interacts with and phosphorylates G6PD at Tyr 112. This phosphorylation enhances catalytic activity of G6PD by dramatically decreasing its Km value and increasing its Kcat value for substrate glucose-6-phosphate. Activated G6PD therefore augments the PPP flux for NADPH and ribose-5-phosphate production which is required for detoxification of intracellular reactive oxygen species (ROS) and biosynthesis of cancer cells, and eventually contributes to tumorigenesis. Consistently, c-Src activation is closely correlated with tyrosine phosphorylation and activity of G6PD in clinical colorectal cancer samples. We thus uncover another aspect of c-Src in promoting cell proliferation and tumorigenesis, deepening our understanding of c-Src as a proto-oncogene.

An organelle-directed chemical ligation approach enables dual-color detection of mitophagy.

Dysfunctional organelles and defective turnover of organelles are engaged in multiple human diseases, but are elusive to image with conventional organelle probes. To overcome this, we developed intra-mitochondrial CLICK to assess mitophagy (IMCLAM), using a pair of conventional ΔΨm probes, where each probe alone fails to track dysfunctional mitochondria. The in situ formed optical triad is stably trapped in mitochondria without resorting to ΔΨm. Utilizing an acidity-responsive ΔΨm probe, IMCLAM enabled fluorescence-on detection of mitophagy by sensing pH acidification upon delivery of mitochondria into lysosomes. Moreover, we applied IMCLAM to assay mitophagy induced by pharmacological compounds in living cells and wild-type zebrafish embryos. Thus, IMCLAM offers a simplified tool to study mitochondria and mitophagy and provide a basis for screening mitophagy-inducing compounds. Abbreviations: CCCP, carbonyl cyanide m-chlorophenylhydrazone; IMCLAM, intra-mitochondrial CLICK to assess mitophagy; ROX, X-rhodamine; SPAAC, stain-promoted azide-alkyne Click Chemistry; TPP, triphenylphosphonium.

c-Src Promotes Tumorigenesis and Tumor Progression by Activating PFKFB3.

Reprogramming of glucose metabolism is a key event in tumorigenesis and progression. Here, we show that active c-Src stimulates glycolysis by phosphorylating (Tyr194) and activating PFKFB3, a key enzyme that boosts glycolysis by producing fructose-2,6-bisphosphate and activating PFK1. Increased glycolysis intermediates replenish non-oxidative pentose phosphate pathway (PPP) and serine pathway for biosynthesis of cancer cells. PFKFB3 knockout (KO) cells and their counterpart reconstituted with PFKFB3-Y194F show comparably impaired abilities for proliferation, migration, and xenograft formation. Furthermore, PFKFB3-Y194F knockin mice show impaired glycolysis and, mating of these mice with APCmin/+ mice attenuates spontaneous colon cancer formation in APCmin/+ mice. In summary, we identify a specific mechanism by which c-Src mediates glucose metabolism to meet cancer cells' requirements for maximal biosynthesis and proliferation. The PFKFB3-Tyr194 phosphorylation level highly correlates with c-Src activity in clinical tumor samples, indicating its potential as an evaluation for tumor prognosis.

PIR promotes tumorigenesis of breast cancer by upregulating cell cycle activator E2F1.

Pirin (PIR) protein belongs to the superfamily of cupin and is highly conserved between eukaryotic and prokaryotic organisms. It has been reported that PIR is upregulated in various tumors and involved in tumorigenesis. However, its biological functions particularly in promoting tumorigenesis are, to date, poorly characterized. Here we report that knockdown of PIR in MCF7 and MDA-MB-231 cell lines causes a dramatic decrease in cell proliferation and xenograft tumor growth in mice. Mechanistically, the cell cycle activator E2F1 and its target genes cdk4, cdk6, cycE, cycD and DDR1 are remarkably downregulated in PIR depleted cells, leading to G1/S phase arrest. Luciferase reporter assay and chromatin immunoprecipitation assay indicate that PIR can activate E2F1 transcription by binding to its promoter region. Consistent with the observation in PIR knockdown cells, PIR inhibitors markedly inhibit the proliferation of both cell lines. Furthermore, knockdown of PIR significantly decreases the abilities of MCF7 cells for mobility and invasion in vitro and their metastasis in mice, which may be attributed to the decrease of DDR1. In conclusion, PIR stimulates tumorigenesis and progression by activating E2F1 and its target genes. Our finding thus suggests PIR as a potential druggable target for the therapy of cancers with high expression level of PIR.

IDH1 Arg-132 mutant promotes tumor formation through down-regulating p53.

Resistance to apoptosis and uncontrolled proliferation are two hallmarks of cancer cells. p53 is crucial for apoptosis triggered by a broad range of stresses and a well-known gatekeeper for neoplastic transformation. Here we show that oncogenic IDH1 R132H/R132Q mutants robustly inhibit p53 expression and such an effect is attributed to 2-HG production. Mechanistically, 2-hydroxyglutarate (2-HG) stabilizes hypoxia-inducible factor-2α, which in turn activates the expression of miR-380-5p, a characterized microRNA against p53 expression. Rescue expression of p53 can inhibit the proliferation rate and impair the resistance of apoptosis induced by doxorubicin in IDH1 R132Q mouse embryonic fibroblast cells. Furthermore, p53 protein levels correlates negatively with IDH1 R132H levels in human glioma samples. Our results thus shed a new light on how p53 is down-regulated by 2-HG and suggests that impairment of p53-mediated apoptosis contributes to the tumorigenesis driven by IDH1 mutants.