Project description:Caseinolytic protease X (ClpX) is an unfoldase that forms the ClpXP complex with caseinolytic protease P (ClpP), playing a critical role in maintaining mitochondrial protein homeostasis. While targeting ClpP has emerged as a promising cancer intervention strategy, the biological function of ClpX in cancer remains largely unexplored. In this study, we identify elevated expression of CLPX in pancreatic ductal adenocarcinoma (PDAC), which correlates with poor patient prognosis. CLPX knockdown significantly inhibits cell proliferation and disrupts mitochondrial protein homeostasis in PDAC cells. This knockdown also induces mitochondrial oxidative stress, impairs oxidative phosphorylation, and activates the unfolded protein response. CLPX knockdown increases reactive oxygen species (ROS) levels, ferrous ion accumulation, lipid peroxidation, and elevates malonaldehyde content, thus promoting ferroptosis. Furthermore, screening of reported ATPase inhibitors reveals that MSC1094308 binds to ClpX, inhibiting ClpXP-mediated substrate degradation. MSC1094308 induces unfolded protein stress and ferroptosis in PDAC cells. Altogether, our findings suggest that ClpX inhibition represents a potent therapeutic strategy for combating PDAC.
Project description:Loss of LdtJ in Acinetobacter baumannii disrupts cell morphology, downregulates peptidoglycan precursor genes (e.g., dadA, alr), and activates the stringent response, including elevated ppGpp levels and dksA upregulation. These defects are fully suppressed in a ∆ldtJ ∆mla double mutant, implicating the outer membrane lipid transport Mla pathway in compensatory regulation. RNA sequencing revealed that transcriptional changes in the ∆ldtJ mutant are reversed in the double mutant, highlighting a functional interplay between peptidoglycan remodeling and outer membrane lipid asymmetry.
Project description:Here we found that ILF3 prefers to bind telomere R-loops and protects telomere from aberrant homologous recombination. ILF3 knockout induces TERRA aggregation onto telomere and activates telomere DNA damage response (DDR). Furthermore, ILF3 deficiency disrupts telomere homeostasis and induces abnormal ALT-mediated telomere lengthening
Project description:Introduction:Macrophage phagocytosis is crucial for cellular homeostasis and is tightly regulated by stress responses. The ER stress sensor IRE1α, a key unfolded protein response (UPR) regulator, is well-studied, but its role in phagocyte homeostasis remains unknown.Objectives:This study investigates whether IRE1α regulates phagocytosis in macrophages and explores its underlying mechanism, aiming to identify potential therapeutic targets for phagocytosis-related disorders.Methods:We examined IRE1α activation in macrophages during phagocytosis of dextran or platelets. Myeloid-specific IRE1α-knockout mice were used to assess phagocytic function. Mechanistic studies included RIDD analysis to identify IRE1α-dependent mRNA degradation. A mouse model of immune thrombocytopenia (ITP) was employed to evaluate platelet clearance, with pharmacological NR1D1 inhibition (SR8278) tested as a rescue strategy.Results:Phagocytosis specifically activates IRE1α in macrophages, where it maintains phagocytic homeostasis. IRE1α deficiency led to excessive phagocytosis due to uncontrolled lysosomal biogenesis. Mechanistically, IRE1α degrades Nr1d1 mRNA via its RNase activity, suppressing lysosomal expansion. In ITP mice, IRE1α deficiency worsened platelet clearance, while SR8278 treatment rescued this defect.
Project description:T lymphocytes are pivotal in adaptive immunity. The role of trafficking protein particle complex (TRAPPC) in regulating T cell development and homeostasis are unknown. Using CD4cre-Trappc1flox/flox (Trappc1 cKO) mice, we found that Trappc1 deficiency in T cells significantly decreased cell number of naïve T cells in the periphery, whereas thymic T cell development in Trappc1 cKO mice was identical as in WT mice. In the culture assays and mouse models with adoptive transfer of the sorted WT (CD45.1+CD45.2+) and Trappc1 cKO naive T cells (CD45.2+) to CD45.1+ syngeneic mice, Trappc1-deficienct naive T cells showed significantly reduced survival ability compared with WT cells. RNA-seq and molecular studies showed that Trappc1 deficiency in naive T cells reduced protein transport from the endoplasmic reticulum to Golgi apparatus, enhanced unfolded protein responses, increased P53 transcription, intracellular Ca2+, Atf4-CHOP, oxidative phosphorylation and lipid peroxide accumulation, and subsequently led to ferroptosis.
Project description:The ARV1-encoded protein mediates sterol transport from the endoplasmic reticulum (ER) to the plasma membrane. Yeast ARV1 mutants accumulate multiple lipids in the ER and are sensitive to pharmacological modulators of both sterol and sphingolipid metabolism. Using fluorescent and electron microscopy, we demonstrate sterol accumulation, subcellular membrane expansion, elevated lipid droplet formation and vacuolar fragmentation in ARV1 mutants. Motif-based regression analysis of ARV1 deletion transcription profiles indicates activation of Hac1p, an integral component of the UPR. Accordingly, we show constitutive splicing of HAC1 transcripts, induction of a UPR reporter and elevated expression of UPR targets in ARV1 mutants. IRE1, encoding the unfolded protein sensor in the ER lumen, exhibits a lethal genetic interaction with ARV1, indicating a viability requirement for the UPR in cells lacking ARV1. Surprisingly, ARV1 mutants expressing a variant of Ire1p defective in sensing unfolded proteins are viable. Moreover these strains also exhibit constitutive HAC1 splicing that interacts with DTT-mediated perturbation of protein folding. These data suggest a component of UPR induction in arv1? strains is distinct from protein misfolding. Decreased ARV1 expression in murine macrophages also results in UPR induction, particularly up-regulation of activating transcription factor-4, C/EBP homologous protein (CHOP) and apoptosis. Cholesterol loading or inhibition of cholesterol esterification further elevated CHOP expression in ARV1 knockdown cells. Thus, loss or down-regulation of ARV1 disturbs membrane and lipid homeostasis resulting in a disruption of ER integrity, one consequence of which is induction of the UPR. Yeast strains were grown to mid-logarithmic stage (A600=0.5-0.6) for RNA extraction and hybridization on Ye6100 or S98 Affymetrix gene chips. The control array (sample name C) was carried out in duplicate. The ARV1 mutant array (sample name A) was carried out in triplicate. Both ARV1 mutants Ye6100 arrays were compared to the same control Ye6100 array. Strains represent different isolates of the same genotype, mating type and genetic background (w303). Sturley lab collection (SCY) strains include SCY328 and SCY2004 for controls and SCY820 and SCY840 for ARV1 mutants.
Project description:The endoplasmic reticulum (ER) is an organelle associated with lipid metabolism. However, the involvement of the ER in nutritional status-dependent energy homeostasis is largely unknown. The results of this study demonstrate that IRE-1, an ER protein known to be involved in the unfolded protein response, and HSP-4, an ER chaperone, regulate expression of the novel fasting-induced lipases FIL-1 and FIL-2, which induce fat granule hydrolysis upon fasting in C. elegans. RNAi and ectopic expression experiments demostrated that FIL-1 and FIL-2 are both necessary and sufficient for fasting-induced fat granule breakdown. Failure of ire-1 and hsp-4 mutant animals to hydrolyze fat granules during starvation impaired their motility, which was rescued by glucose supplementation of their media, implicating the importance of ire-1/hsp-4-dependent lipolysis for energy supply from stored fat during fasting. Taken together, these data suggest that the ER-resident proteins IRE-1 and HSP-4 are key nutritional sensors that modulate expression of inducible lipases to maintain whole-body energy homeostasis in C. elegans. Synchronized L4 worms were divided into well-fed and 6 hours fasted samples for RNA extraction and hybridization on an Agilent microarray.
Project description:The ARV1-encoded protein mediates sterol transport from the endoplasmic reticulum (ER) to the plasma membrane. Yeast ARV1 mutants accumulate multiple lipids in the ER and are sensitive to pharmacological modulators of both sterol and sphingolipid metabolism. Using fluorescent and electron microscopy, we demonstrate sterol accumulation, subcellular membrane expansion, elevated lipid droplet formation and vacuolar fragmentation in ARV1 mutants. Motif-based regression analysis of ARV1 deletion transcription profiles indicates activation of Hac1p, an integral component of the UPR. Accordingly, we show constitutive splicing of HAC1 transcripts, induction of a UPR reporter and elevated expression of UPR targets in ARV1 mutants. IRE1, encoding the unfolded protein sensor in the ER lumen, exhibits a lethal genetic interaction with ARV1, indicating a viability requirement for the UPR in cells lacking ARV1. Surprisingly, ARV1 mutants expressing a variant of Ire1p defective in sensing unfolded proteins are viable. Moreover these strains also exhibit constitutive HAC1 splicing that interacts with DTT-mediated perturbation of protein folding. These data suggest a component of UPR induction in arv1? strains is distinct from protein misfolding. Decreased ARV1 expression in murine macrophages also results in UPR induction, particularly up-regulation of activating transcription factor-4, C/EBP homologous protein (CHOP) and apoptosis. Cholesterol loading or inhibition of cholesterol esterification further elevated CHOP expression in ARV1 knockdown cells. Thus, loss or down-regulation of ARV1 disturbs membrane and lipid homeostasis resulting in a disruption of ER integrity, one consequence of which is induction of the UPR.
Project description:Biological membranes have a stunning ability to adapt their composition in response to physiological stress and metabolic challenges. Little is known how such perturbations affect individual organelles in eukaryotic cells. Pioneering work provided insights into the subcellular distribution of lipids in the yeast Saccharomyces cerevisiae, but the composition of the endoplasmic reticulum (ER) membrane, which also crucially regulates lipid metabolism and the unfolded protein response, remained insufficiently characterized. Here we describe a method for purifying organelle membranes from yeast, MemPrep. We demonstrate the purity of our ER membrane preparations by proteomics and document the general utility of MemPrep by isolating vacuolar membranes. Quantitative lipidomics establishes the lipid composition of the ER and the vacuolar membrane. Our findings provide a baseline for studying membrane protein biogenesis and have important implications for understanding the role of lipids in regulating the unfolded protein response (UPR). The combined preparative and analytical MemPrep approach uncovers a dynamic remodeling of ER membranes in stressed cells and establishes distinct molecular fingerprints of lipid bilayer stress.