-
Advanced Science (Weinheim,... May 2024Targeting cancer-specific metabolic processes is a promising therapeutic strategy. Here, this work uses a compound library that directly inhibits metabolic enzymes to...
Targeting cancer-specific metabolic processes is a promising therapeutic strategy. Here, this work uses a compound library that directly inhibits metabolic enzymes to screen the potential metabolic targets in lung adenocarcinoma (LUAD). SHIN1, the specific inhibitor of serine hydroxymethyltransferase 1/2 (SHMT1/2), has a highly specific inhibitory effect on LUAD cells, and this effect depends mainly on the overexpression of SHMT2. This work clarifies that mitogen-activated protein kinase 1 (MAPK1)-mediated phosphorylation at Ser90 is the key mechanism underlying SHMT2 upregulation in LUAD and that this phosphorylation stabilizes SHMT2 by reducing STIP1 homology and U-box containing protein 1 (STUB1)-mediated ubiquitination and degradation. SHMT2-Ser90 dephosphorylation decreases S-adenosylmethionine levels in LUAD cells, resulting in reduced N-methyladenosine (mA) levels in global RNAs without affecting total protein or DNA methylation. Methylated RNA immunoprecipitation sequencing (MeRIP-Seq) and RNA sequencing (RNA-Seq) analyses further demonstrate that SHMT2-Ser90 dephosphorylation accelerates the RNA degradation of oncogenic genes by reducing mA modification, leading to the inhibition of tumorigenesis. Overall, this study elucidates a new regulatory mechanism of SHMT2 during oncogenesis and provides a theoretical basis for targeting SHMT2 as a therapeutic target in LUAD.
Topics: Animals; Humans; Mice; Adenocarcinoma of Lung; Adenosine; Carcinogenesis; Cell Line, Tumor; Disease Models, Animal; Glycine Hydroxymethyltransferase; Lung Neoplasms; Phosphorylation
PubMed: 38460155
DOI: 10.1002/advs.202307834 -
Biomedicine & Pharmacotherapy =... Apr 2024Breast cancer has become the most prevalent malignancy worldwide; however, therapeutic efficacy is far from satisfactory. To alleviate the burden of this disease, it is... (Review)
Review
Breast cancer has become the most prevalent malignancy worldwide; however, therapeutic efficacy is far from satisfactory. To alleviate the burden of this disease, it is imperative to discover novel mechanisms and treatment strategies. Protein phosphatase 2 A (PP2A) comprises a family of mammalian serine/threonine phosphatases that regulate many cellular processes. PP2A is dysregulated in several human diseases, including oncological pathologies, and plays a pivotal role in the initiation and progression of tumours. The role of PP2A as a tumour suppressor has been extensively studied, and its regulation can serve as a target for anticancer therapy. Recent studies have shown that PP2A is a tumour promotor. PP2A-mediated anticancer therapy may involve two opposing mechanisms: activation and inhibition. In general, the contradictory roles of PP2A should not be overlooked, and more work is needed to determine the molecular mechanism by which PP2A affects in tumours. In this review, the literature on the role of PP2A in tumours, especially in breast cancer, was analysed. This review describes relevant targets of breast cancer, such as cell cycle control, DNA damage responses, epidermal growth factor receptor, immune modulation and cell death resistance, which may lead to effective therapeutic strategies or influence drug development in breast cancer.
Topics: Female; Humans; Breast Neoplasms; Protein Phosphatase 2
PubMed: 38458011
DOI: 10.1016/j.biopha.2024.116398 -
PLoS Genetics Mar 2024To sustain growth in changing nutrient conditions, cells reorganize outputs of metabolic networks and appropriately reallocate resources. Signaling by reversible protein...
To sustain growth in changing nutrient conditions, cells reorganize outputs of metabolic networks and appropriately reallocate resources. Signaling by reversible protein phosphorylation can control such metabolic adaptations. In contrast to kinases, the functions of phosphatases that enable metabolic adaptation as glucose depletes are poorly studied. Using a Saccharomyces cerevisiae deletion screen, we identified the PP2A-like phosphatase Ppg1 as required for appropriate carbon allocations towards gluconeogenic outputs-trehalose, glycogen, UDP-glucose, UDP-GlcNAc-after glucose depletion. This Ppg1 function is mediated via regulation of the assembly of the Far complex-a multi-subunit complex that tethers to the ER and mitochondrial outer membranes forming localized signaling hubs. The Far complex assembly is Ppg1 catalytic activity-dependent. Ppg1 regulates the phosphorylation status of multiple ser/thr residues on Far11 to enable the proper assembly of the Far complex. The assembled Far complex is required to maintain gluconeogenic outputs after glucose depletion. Glucose in turn regulates Far complex amounts. This Ppg1-mediated Far complex assembly, and Ppg1-Far complex dependent control of gluconeogenic outputs enables adaptive growth under glucose depletion. Our study illustrates how protein dephosphorylation is required for the assembly of a multi-protein scaffold present in localized cytosolic pools, to thereby alter gluconeogenic flux and enable cells to metabolically adapt to nutrient fluctuations.
Topics: Glucose; Saccharomyces cerevisiae Proteins; Protein Phosphatase 2; Saccharomyces cerevisiae; Signal Transduction; Phosphorylation
PubMed: 38452140
DOI: 10.1371/journal.pgen.1011202 -
Alzheimer's & Dementia : the Journal of... Apr 2024Tau phosphorylated at threonine-217 (pT217-tau) is a novel fluid-based biomarker that predicts onset of Alzheimer's disease (AD) symptoms, but little is known about how...
Nanoscale imaging of pT217-tau in aged rhesus macaque entorhinal and dorsolateral prefrontal cortex: Evidence of interneuronal trafficking and early-stage neurodegeneration.
INTRODUCTION
Tau phosphorylated at threonine-217 (pT217-tau) is a novel fluid-based biomarker that predicts onset of Alzheimer's disease (AD) symptoms, but little is known about how pT217-tau arises in the brain, as soluble pT217-tau is dephosphorylated post mortem in humans.
METHODS
We used multilabel immunofluorescence and immunoelectron microscopy to examine the subcellular localization of early-stage pT217-tau in entorhinal and prefrontal cortices of aged macaques with naturally occurring tau pathology and assayed pT217-tau levels in plasma.
RESULTS
pT217-tau was aggregated on microtubules within dendrites exhibiting early signs of degeneration, including autophagic vacuoles. It was also seen trafficking between excitatory neurons within synapses on spines, where it was exposed to the extracellular space, and thus accessible to cerebrospinal fluid (CSF)/blood. Plasma pT217-tau levels increased across the age span and thus can serve as a biomarker in macaques.
DISCUSSION
These data help to explain why pT217-tau predicts degeneration in AD and how it gains access to CSF and plasma to serve as a fluid biomarker.
Topics: Animals; Alzheimer Disease; Amyloid beta-Peptides; Biomarkers; Dorsolateral Prefrontal Cortex; Macaca mulatta; tau Proteins
PubMed: 38445818
DOI: 10.1002/alz.13737 -
Frontiers in Cellular Neuroscience 2024Mechanisms of tissue damage in Huntington's disease (HD) involve excitotoxicity, mitochondrial damage, and neuroinflammation, including microglia activation. CD47 is a...
Mechanisms of tissue damage in Huntington's disease (HD) involve excitotoxicity, mitochondrial damage, and neuroinflammation, including microglia activation. CD47 is a membrane protein that interacts with the inhibitory immunoreceptor SIRPα. Engagement of SIRPα by CD47 provides a downregulatory signal that inhibits host cell phagocytosis, promoting a "don't-eat-me" signal. These proteins are involved in the immune response and are downmodulated in inflammatory diseases. The involvement of inflammation and of the inflammasome in HD has already been described. In this study, we focused on other factors that can be involved in the unregulated inflammatory response that accelerates and exacerbate the neurodegenerative process in HD. Our results show that CD47 on striatal neurons decreased in HD mice, while it increased in wild type mice with age. SIRPα, on the other hand, was present in neurons in the wild type and increases in the R6/2 mice at all stages. Recruitment of SIRPα and binding to CD47 promotes the activation through phosphorylating events of non-receptor protein tyrosine phosphatase SHP-1 and SHP-2 in neurons and microglia. SHP phosphatases are able to curb the activity of NLRP3 inflammasome thereby reducing the detrimental effect of neuroinflammation. Such activity is mediated by the inhibition (dephosphorylation) of the proteins signal transducer and activator of transcription (STAT). We found that activated SHP-1 was present in microglia and neurons of WT mice at 5 and 13 weeks, increasing with time; while in R6/2 it was not localized in neurons but only in microglia, where it decreases with time. Consequently, STAT1 was overexpressed in neurons of R6/2 mice, as an effect of lack of modulation by SHP-1. Thus, our results shed light on the pathophysiology of neuronal damage, on one hand, paving the way toward a modulation of signal transducer proteins by specific inhibitors to achieve neuroprotection in HD, on the other.
PubMed: 38444595
DOI: 10.3389/fncel.2024.1360066 -
MSystems Apr 2024species are able to produce and release secreted proteins, such as toxins, adhesins, and virulence-related enzymes, involved in bacteria adhesion, invasion, and immune...
UNLABELLED
species are able to produce and release secreted proteins, such as toxins, adhesins, and virulence-related enzymes, involved in bacteria adhesion, invasion, and immune evasion between the pathogen and host. Here, we investigated a novel secreted protein, MbovP0725, from encoding a putative haloacid dehalogenase (HAD) hydrolase function of a key serine/threonine phosphatase depending on Mg for the dephosphorylation of its substrate and it was most active at pH 8 to 9 and temperatures around 40°C. A transposon insertion mutant strain of HB0801 that lacked the protein MbovP0725 induced a stronger inflammatory response but with a partial reduction of adhesion ability. Using transcriptome sequencing and quantitative reverse transcription polymerase chain reaction analysis, we found that the mutant was upregulated by the mRNA expression of genes from the glycolysis pathway, while downregulated by the genes enriched in ABC transporters and acetate kinase-phosphate acetyltransferase pathway. Untargeted metabolomics showed that the disruption of the gene caused the accumulation of 9-hydroxyoctadecadienoic acids and the consumption of cytidine 5'-monophosphate, uridine monophosphate, and adenosine monophosphate. Both the exogenous and endogenous MbvoP0725 protein created by purification and transfection inhibited lipopolysaccharide (LPS)-induced IL-1β, IL-6, and TNF-α mRNA production and could also attenuate the activation of MAPK-associated pathways after LPS treatment. A pull-down assay identified MAPK p38 and ERK as potential substrates for MbovP0725. These findings define metabolism- and virulence-related roles for a HAD family phosphatase and reveal its ability to inhibit the host pro-inflammatory response.
IMPORTANCE
() infection is characterized by chronic pneumonia, otitis, arthritis, and mastitis, among others, and tends to involve the suppression of the immune response via multiple strategies to avoid host cell immune clearance. This study found that MbovP0725, a haloacid dehalogenase (HAD) family phosphatase secreted by , had the ability to inhibit the host pro-inflammatory response induced by lipopolysaccharide. Transcriptomic and metabolomic analyses were used to identify MbovP0725 as an important phosphatase involved in glycolysis and nucleotide metabolism. The transposon mutant strain T8.66 lacking MbovP0725 induced a higher inflammatory response and exhibited weaker adhesion to host cells. Additionally, T8.66 attenuated the phosphorylation of MAPK P38 and ERK and interacted with the two targets. These results suggested that MbovP0725 had the virulence- and metabolism-related role of a HAD family phosphatase, performing an anti-inflammatory response during infection.
Topics: Female; Humans; Mycoplasma bovis; Lipopolysaccharides; Bacterial Adhesion; Mycoplasma Infections; Immunity; Phosphoprotein Phosphatases; RNA, Messenger; Serine
PubMed: 38440990
DOI: 10.1128/msystems.00891-23 -
The Biochemical Journal Apr 2024The protein kinase Gcn2 and its effector protein Gcn1 are part of the general amino acid control signalling (GAAC) pathway best known in yeast for its function in...
The protein kinase Gcn2 and its effector protein Gcn1 are part of the general amino acid control signalling (GAAC) pathway best known in yeast for its function in maintaining amino acid homeostasis. Under amino acid limitation, Gcn2 becomes activated, subsequently increasing the levels of phosphorylated eIF2α (eIF2α-P). This leads to the increased translation of transcriptional regulators, such as Gcn4 in yeast and ATF4 in mammals, and subsequent re-programming of the cell's gene transcription profile, thereby allowing cells to cope with starvation. Xrn1 is involved in RNA decay, quality control and processing. We found that Xrn1 co-precipitates Gcn1 and Gcn2, suggesting that these three proteins are in the same complex. Growth under starvation conditions was dependent on Xrn1 but not on Xrn1-ribosome association, and this correlated with reduced eIF2α-P levels. Constitutively active Gcn2 leads to a growth defect due to eIF2α-hyperphosphorylation, and we found that this phenotype was independent of Xrn1, suggesting that xrn1 deletion does not enhance eIF2α de-phosphorylation. Our study provides evidence that Xrn1 is required for efficient Gcn2 activation, directly or indirectly. Thus, we have uncovered a potential new link between RNA metabolism and the GAAC.
Topics: Amino Acids; Eukaryotic Initiation Factor-2; Mammals; Peptide Elongation Factors; Phosphorylation; Protein Serine-Threonine Kinases; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Exoribonucleases
PubMed: 38440860
DOI: 10.1042/BCJ20220531 -
Bone Research Mar 2024Osteoarthritis (OA) is a common degenerative disease worldwide and new therapeutics that target inflammation and the crosstalk between immunocytes and chondrocytes are...
Osteoarthritis (OA) is a common degenerative disease worldwide and new therapeutics that target inflammation and the crosstalk between immunocytes and chondrocytes are being developed to prevent and treat OA. These attempts involve repolarizing pro-inflammatory M1 macrophages into the anti-inflammatory M2 phenotype in synovium. In this study, we found that phosphoglycerate mutase 5 (PGAM5) significantly increased in macrophages in OA synovium compared to controls based on histology of human samples and single-cell RNA sequencing results of mice models. To address the role of PGAM5 in macrophages in OA, we found conditional knockout of PGAM5 in macrophages greatly alleviated OA symptoms and promoted anabolic metabolism of chondrocytes in vitro and in vivo. Mechanistically, we found that PGAM5 enhanced M1 polarization via AKT-mTOR/p38/ERK pathways, whereas inhibited M2 polarization via STAT6-PPARγ pathway in murine bone marrow-derived macrophages. Furthermore, we found that PGAM5 directly dephosphorylated Dishevelled Segment Polarity Protein 2 (DVL2) which resulted in the inhibition of β-catenin and repolarization of M2 macrophages into M1 macrophages. Conditional knockout of both PGAM5 and β-catenin in macrophages significantly exacerbated osteoarthritis compared to PGAM5-deficient mice. Motivated by these findings, we successfully designed mannose modified fluoropolymers combined with siPGAM5 to inhibit PGAM5 specifically in synovial macrophages via intra-articular injection, which possessed desired targeting abilities of synovial macrophages and greatly attenuated murine osteoarthritis. Collectively, these findings defined a key role for PGAM5 in orchestrating macrophage polarization and provides insights into novel macrophage-targeted strategy for treating OA.
Topics: Humans; Animals; Mice; Phosphoglycerate Mutase; beta Catenin; Osteoarthritis; Inflammation; Macrophages; Phosphoprotein Phosphatases; Mitochondrial Proteins
PubMed: 38433252
DOI: 10.1038/s41413-024-00318-8 -
Cancer Cell International Mar 2024Patients with colorectal cancer (CRC) with liver metastasis or drug resistance have a poor prognosis. Previous research has demonstrated that PPP2R1B inactivation...
BACKGROUND
Patients with colorectal cancer (CRC) with liver metastasis or drug resistance have a poor prognosis. Previous research has demonstrated that PPP2R1B inactivation results in the development of CRC. However, the role of PPP2R1B in CRC metastasis and drug resistance is unclear.
METHODS
Venny 2.1 was used to determine the intersection between survival-related differentially expressed genes (DEGs) and liver metastasis-related DEGs according to RNA-seq data from The Cancer Genome Atlas (TCGA) and the GEO database (GSE179979). LC‒MS/MS and coimmunoprecipitation were performed to predict and verify the substrate protein of PPP2R1B. Gene Set Variation Analysis (GSVA) was subsequently utilized to assess pathway enrichment levels. The predictive performance of PPP2R1B was assessed by regression analysis, Kaplan-Meier (KM) survival analysis and drug sensitivity analysis. Immunohistochemistry (IHC), qRT-PCR and western blotting were performed to measure the expression levels of related mRNAs or proteins. Biological features were evaluated by wound healing, cell migration and invasion assays and CCK-8 assays. A mouse spleen infection liver metastasis model was generated to confirm the role of PPP2R1B in the progression of liver metastasis in vivo.
RESULTS
According to bioinformatics analysis, PPP2R1B is significantly associated with liver metastasis and survival in CRC patients, and these findings were further verified via immunohistochemistry (IHC), qPCR and Western blotting. Pathway enrichment and LC‒MS/MS analysis revealed that PPP2R1B is negatively associated with the MAPK/ERK signalling pathway. Additionally, PD98059, a MAPK/ERK pathway inhibitor, inhibited EMT in vitro by reversing the changes in key proteins involved in EMT signalling (ZEB1, E-cadherin and Snail) and ERK/MAPK signalling (p-ERK) mediated by PPP2R1B. Oxaliplatin sensitivity prediction and validation revealed that PPP2R1B silencing decreased Oxaliplatin chemosensitivity, and these effects were reversed by PD98059 treatment. Moreover, PPP2R1B was coimmunoprecipitated with p-ERK in vitro. A negative correlation between PPP2R1B and p-ERK expression was also observed in clinical CRC samples, and the low PPP2R1B/high p-ERK coexpression pattern indicated a poor prognosis in CRC patients. In vivo, PPP2R1B silencing significantly promoted liver metastasis.
CONCLUSIONS
This study revealed that PPP2R1B induces dephosphorylation of the p-ERK protein, inhibits liver metastasis and increases Oxaliplatin sensitivity in CRC patients and could be a potential candidate for therapeutic application in CRC.
PubMed: 38429738
DOI: 10.1186/s12935-024-03273-w -
Cell Communication and Signaling : CCS Feb 2024Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and...
BACKGROUND
Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known.
METHODS
We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting.
RESULTS
We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis.
CONCLUSION
Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.
Topics: Signal Transduction; Phosphorylation; Proto-Oncogene Proteins c-akt; Phosphatidylinositol 3-Kinases; Apoptosis
PubMed: 38419089
DOI: 10.1186/s12964-024-01536-7