Differential heat-response characteristics of two plastid isoforms of triose phosphate isomerase in tomato.

Heat stress causes dysfunction of the carbon-assimilation metabolism. As a member of Calvin-Benson-Bassham (CBB) cycle, the chloroplast triose phosphate isomerases (TPI) catalyse the interconversion of glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP). The tomato (Solanum lycopersicum) genome contains two individual SlTPI genes, Solyc10g054870 and Solyc01g111120, which encode the chloroplast-located proteins SlTPI1 and SlTPI2, respectively. The tpi1 and tpi2 single mutants had no visible phenotypes, but the leaves of their double mutant lines tpi1tpi2 had obviously reduced TPI activity and displayed chlorotic variegation, dysplasic chloroplasts and lower carbon-assimilation efficiency. In addition to altering carbon metabolism, proteomic data showed that the loss of both SlTPI1 and SlTPI2 severely affected photosystem proteins, reducing photosynthetic capacity. None of these phenotypes was evident in the tpi1 or tpi2 single mutants, suggesting that SlTPI1 and SlTPI2 are functionally redundant. However, the two proteins differed in their responses to heat stress; the protein encoded by the heat-induced SlTPI2 showed a higher level of thermotolerance than that encoded by the heat-suppressed SlTPI1. Notably, heat-induced transcription factors, SlWRKY21 and SlHSFA2/7, which negatively regulated SlTPI1 expression and positively regulated SlTPI2 expression, respectively. Our findings thus reveal that SlTPI1 and SlTPI2 have different thermostabilities and expression patterns in response to heat stress, which have the potential to be applied in thermotolerance strategies in crops.

Triosephosphate isomerase 1 may be a risk predictor in laryngeal squamous cell carcinoma: a multi-centered study integrating bulk RNA, single-cell RNA, and protein immunohistochemistry.

BACKGROUND: Although great progress has been made in anti-cancer therapy, the prognosis of laryngeal squamous cell carcinoma (LSCC) patients remains unsatisfied. Quantities of studies demonstrate that glycolytic reprograming is essential for the progression of cancers, where triosephosphate isomerase 1 (TPI1) serves as a catalytic enzyme. However, the clinicopathological significance and potential biological functions of TPI1 underlying LSCC remains obscure. METHODS: We collected in-house 82 LSCC tissue specimens and 56 non-tumor tissue specimens. Tissue microarrays (TMA) and immunohistochemical (IHC) experiments were performed. External LSCC microarrays and bulk RNA sequencing data were integrated to evaluate the expression of TPI1. We used a log-rank test and the CIBERSORT algorithm to assess the prognostic value of TPI1 and its association with the LSCC microenvironment. Malignant laryngeal epithelial cells and immune-stromal cells were identified using inferCNV and CellTypist. We conducted a comprehensive analysis to elucidate the molecular functions of TPI1 in LSCC tissue and single cells using Pearson correlation analysis, high dimensional weighted gene co-expression analysis, gene set enrichment analysis, and clustered regularly interspaced short palindromic repeats (CRISPR) screen. We explored intercellular communication patterns between LSCC single cells and immune-stromal cells and predicted several therapeutic agents targeting TPI1. RESULTS: Based on the in-house TMA and IHC analysis, TPI1 protein was found to have a strong positive expression in the nucleus of LSCC cells but only weakly positive activity in the cytoplasm of normal laryngeal cells (p < 0.0001). Further confirmation of elevated TPI1 mRNA expression was obtained from external datasets, comparing 251 LSCC tissue samples to 136 non-LSCC tissue samples (standardized mean difference = 1.06). The upregulated TPI1 mRNA demonstrated a high discriminative ability between LSCC and non-LSCC tissue (area under the curve = 0.91; sensitivity = 0.87; specificity = 0.79), suggesting its potential as a predictive marker for poor prognosis (p = 0.037). Lower infiltration abundance was found for plasma cells, naïve B cells, monocytes, and neutrophils in TPI-high expression LSCC tissue. Glycolysis and cell cycle were significantly enriched pathways for both LSCC tissue and single cells, where heat shock protein family B member 1, TPI1, and enolase 1 occupied a central position. Four outgoing communication patterns and two incoming communication patterns were identified from the intercellular communication networks. TPI1 was predicted as an oncogene in LSCC, with CRISPR scores less than -1 across 71.43% of the LSCC cell lines. TPI1 was positively correlated with the half maximal inhibitory concentration of gemcitabine and cladribine. CONCLUSIONS: TPI1 is dramatically overexpressed in LSCC than in normal tissue, and the high expression of TPI1 may promote LSCC deterioration through its metabolic and non-metabolic functions. This study contributes to advancing our knowledge of LSCC pathogenesis and may have implications for the development of targeted therapies in the future.

Kinetics and mechanism for enzyme-catalyzed reactions of substrate pieces.

The most important difference between enzyme and small molecule catalysts is that only enzymes utilize the large intrinsic binding energies of nonreacting portions of the substrate in stabilization of the transition state for the catalyzed reaction. A general protocol is described to determine the intrinsic phosphodianion binding energy for enzymatic catalysis of reactions of phosphate monoester substrates, and the intrinsic phosphite dianion binding energy in activation of enzymes for catalysis of phosphodianion truncated substrates, from the kinetic parameters for enzyme-catalyzed reactions of whole and truncated substrates. The enzyme-catalyzed reactions so-far documented that utilize dianion binding interactions for enzyme activation; and, their phosphodianion truncated substrates are summarized. A model for the utilization of dianion binding interactions for enzyme activation is described. The methods for the determination of the kinetic parameters for enzyme-catalyzed reactions of whole and truncated substrates, from initial velocity data, are described and illustrated by graphical plots of kinetic data. The results of studies on the effect of site-directed amino acid substitutions at orotidine 5'-monophosphate decarboxylase, triosephosphate isomerase, and glycerol-3-phosphate dehydrogenase provide strong support for the proposal that these enzymes utilize binding interactions with the substrate phosphodianion to hold the protein catalysts in reactive closed conformations.

Phosphorylation and acetylation responses of glycolytic enzymes in meat to different chilling rates.

The aim of this study was to investigate the effects of chilling rate on phosphorylation and acetylation levels of the glycolytic enzymes in meat, including glycogen phosphorylase, phosphofructokinase, aldolase (ALDOA), triose-phosphate isomerase (TPI1), phosphoglycerate kinase, lactate dehydrogenase (LDH). The samples were assigned into three groups: Control, Chilling 1 and Chilling 2, corresponding to the chilling rates of 4.8 °C/h, 23.0 °C/h and 25.1 °C/h respectively. The contents of glycogen and ATP were significantly higher in samples from the chilling groups. The activity and phosphorylation level of the six enzymes were higher in samples at the chilling rate of 25.1 °C/h, while the acetylation level of ALDOA, TPI1 and LDH were inhibited. In brief, glycolysis was delayed and the activity of glycolytic enzymes were maintained at higher level by the changes of phosphorylation and acetylation levels at the chilling rates of 23.0 °C/h and 25.1 °C/h, which may partly explain why very fast chilling improves meat quality.

[Triose phosphate isomerase deficiency: a rare erythrocyte enzymopathy with a poor prognosis]. / Le déficit en triose phosphate isomérase : une enzymopathie érythrocytaire rare et de pronostic sombre.

Triose phosphate isomerase (TPI) is a crucial enzyme for glycolysis. TPI deficiency is an autosomal recessive metabolic disease described in 1965, which remains exceptional by its rarity (less than 100 cases described worldwide), but by its extreme severity. Indeed, it is characterized by a chronic hemolytic anemia, an increased susceptibility to infections and especially, a progressive neurological degeneration which leads to death in early childhood for the majority of cases. We report in our observation the history of diagnosis and clinical course of monozygotic twins born at 32 WA with triose phosphate isomerase deficiency.

LKB1-Dependent Regulation of TPI1 Creates a Divergent Metabolic Liability between Human and Mouse Lung Adenocarcinoma.

KRAS is the most frequently mutated oncogene in human lung adenocarcinomas (hLUAD), and activating mutations frequently co-occur with loss-of-function mutations in TP53 or STK11/LKB1. However, mutation of all three genes is rarely observed in hLUAD, even though engineered comutation is highly aggressive in mouse lung adenocarcinoma (mLUAD). Here, we provide a mechanistic explanation for this difference by uncovering an evolutionary divergence in the regulation of triosephosphate isomerase (TPI1). In hLUAD, TPI1 activity is regulated via phosphorylation at Ser21 by the salt inducible kinases (SIK) in an LKB1-dependent manner, modulating flux between the completion of glycolysis and production of glycerol lipids. In mice, Ser21 of TPI1 is a Cys residue that can be oxidized to alter TPI1 activity without a need for SIKs or LKB1. Our findings suggest this metabolic flexibility is critical in rapidly growing cells with KRAS and TP53 mutations, explaining why the loss of LKB1 creates a liability in these tumors. SIGNIFICANCE: Utilizing phosphoproteomics and metabolomics in genetically engineered human cell lines and genetically engineered mouse models (GEMM), we uncover an evolutionary divergence in metabolic regulation within a clinically relevant genotype of human LUAD with therapeutic implications. Our data provide a cautionary example of the limits of GEMMs as tools to study human diseases such as cancers. This article is highlighted in the In This Issue feature, p. 799.

Structure of lactate oxidase from Enterococcus hirae revealed new aspects of active site loop function: Product-inhibition mechanism and oxygen gatekeeper.

l-Lactate oxidase (LOx) is a flavin mononucleotide (FMN)-dependent triose phosphate isomerase (TIM) barrel fold enzyme that catalyzes the oxidation of l-lactate using oxygen as a primary electron acceptor. Although reductive half-reaction mechanism of LOx has been studied by structure-based kinetic studies, oxidative half-reaction and substrate/product-inhibition mechanisms were yet to be elucidated. In this study, the structure and enzymatic properties of wild-type and mutant LOxs from Enterococcus hirae (EhLOx) were investigated. EhLOx structure showed the common TIM-barrel fold with flexible loop region. Noteworthy observations were that the EhLOx crystal structures prepared by co-crystallization with product, pyruvate, revealed the complex structures with "d-lactate form ligand," which was covalently bonded with a Tyr211 side chain. This observation provided direct evidence to suggest the product-inhibition mode of EhLOx. Moreover, this structure also revealed a flip motion of Met207 side chain, which is located on the flexible loop region as well as Tyr211. Through a saturation mutagenesis study of Met207, one of the mutants Met207Leu showed the drastically decreased oxidase activity but maintained dye-mediated dehydrogenase activity. The structure analysis of EhLOx Met207Leu revealed the absence of flipping in the vicinity of FMN, unlike the wild-type Met207 side chain. Together with the simulation of the oxygen-accessible channel prediction, Met207 may play as an oxygen gatekeeper residue, which contributes oxygen uptake from external enzyme to FMN. Three clades of LOxs are proposed based on the difference of the Met207 position and they have different oxygen migration pathway from external enzyme to active center FMN.

Ligand-Based Virtual Screening and Molecular Docking of Benzimidazoles as Potential Inhibitors of Triosephosphate Isomerase Identified New Trypanocidal Agents.

Trypanosoma cruzi (T. cruzi) is a parasite that affects humans and other mammals. T. cruzi depends on glycolysis as a source of adenosine triphosphate (ATP) supply, and triosephosphate isomerase (TIM) plays a key role in this metabolic pathway. This enzyme is an attractive target for the design of new trypanocidal drugs. In this study, a ligand-based virtual screening (LBVS) from the ZINC15 database using benzimidazole as a scaffold was accomplished. Later, a molecular docking on the interface of T. cruzi TIM (TcTIM) was performed and the compounds were grouped by interaction profiles. Subsequently, a selection of compounds was made based on cost and availability for in vitro evaluation against blood trypomastigotes. Finally, the compounds were analyzed by molecular dynamics simulation, and physicochemical and pharmacokinetic properties were determined using SwissADME software. A total of 1604 molecules were obtained as potential TcTIM inhibitors. BP2 and BP5 showed trypanocidal activity with half-maximal lytic concentration (LC50) values of 155.86 and 226.30 µM, respectively. Molecular docking and molecular dynamics simulation analyzes showed a favorable docking score of BP5 compound on TcTIM. Additionally, BP5 showed a low docking score (-5.9 Kcal/mol) on human TIM compared to the control ligand (-7.2 Kcal/mol). Both compounds BP2 and BP5 showed good physicochemical and pharmacokinetic properties as new anti-T. cruzi agents.

Co-culture with osteoblasts up-regulates glycolysis of chondrocytes through MAPK/HIF-1 pathway.

It is well recognized that the neighbor location between cartilage layer and subchondral bone facilitates the intercellular communication and material exchange. However, the evidence that demonstrates the influence of direct communication between cartilage and subchondral bone on their cell behaviors are still partially unknown. In the current study, we established a co-culture system of chondrocytes and osteoblasts aiming to explore the changes of intracellular metabolism of chondrocytes induced by osteoblasts. By using lactate assay kit, RNA sequencing, qRT-PCR and western blot, we found that osteoblasts enhanced the glycolysis in chondrocytes by characterizing the changes of lactate secretion and cytoplasmic expression, and gene expressions including glucose-6-phosphate isomerase 1 (Gpi1), phosphofructokinase, liver type (Pfkl), lactate dehydrogenase A (Ldha), aldolase, fructose-bisphosphate C (Aldoc), phosphoglycerate kinase 1 (Pgk1), glyceraldehyde-3-phosphate dehydrogenase (Gapdh) and triosephosphate isomerase 1 (Tpi1). The enhanced glycolysis might be due to the activation of HIF-1 signaling and its downstream target, pyruvate dehydrogenase kinase1 (PDK1), by qRT-PCR, western blot and immunofluorescence. We also detected the up-regulation of ERK and p38/MAPK upstream signaling in chondrocytes induced by osteoblasts by western blot and immunofluorescence. The enhanced glycolysis in chondrocytes induced by osteoblasts could help us to better understand the intracellular metabolic mechanism of chondrocytes and cartilage disease occurrence.

Triosephosphate Isomerase and Its Product Glyceraldehyde-3-Phosphate Are Involved in the Regulatory Mechanism That Suppresses Exit from the Quiescent State in Yeast Cells.

Cells of the budding yeast Saccharomyces cerevisiae form spores or stationary cells upon nutrient starvation. These quiescent cells are known to resume mitotic growth in response to nutrient signals, but the mechanism remains elusive. Here, we report that quiescent yeast cells are equipped with a negative regulatory mechanism which suppresses the commencement of mitotic growth. The regulatory process involves a glycolytic enzyme, triosephosphate isomerase (Tpi1), and its product, glyceraldehyde-3-phosphate (GAP). GAP serves as an inhibitory signaling molecule; indeed, the return to growth of spores or stationary cells is suppressed by the addition of GAP even in nutrient-rich growth media, though mitotic cells are not affected. Reciprocally, dormancy is abolished by heat treatment because of the heat sensitivity of Tpi1. For example, spores commence germination merely upon heat treatment, which indicates that the negative regulatory mechanism is actively required for spores to prevent premature germination. Stationary cells of Candida glabrata are also manipulated by heat and GAP, suggesting that the regulatory process is conserved in the pathogenic yeast. IMPORTANCE Our results suggest that, in quiescent cells, nutrient signals do not merely provoke a positive regulatory process to commence mitotic growth. Exit from the quiescent state in yeast cells is regulated by balancing between the positive and negative signaling pathways. Identifying the negative regulatory pathway would provide new insight into the regulation of the transition from the quiescent to the mitotic state. Clinically, quiescent cells are problematic because they are resistant to environmental stresses and antibiotics. Given that the quiescent state is modulated by manipulation of the negative regulatory mechanism, understanding this process is important not only for its biological interest but also as a potential target for antifungal treatment.

Overexpression of Chloroplast Triosephosphate Isomerase Marginally Improves Photosynthesis at Elevated CO2 Levels in Rice.

We recently suggested that chloroplast triosephosphate isomerase (cpTPI) has moderate control over the rate of CO2 assimilation (A) at elevated CO2 levels via the capacity for triose phosphate utilization (TPU) in rice (Oryza sativa L.) from its antisense-suppression study. In the present study, the effects of cpTPI overexpression on photosynthesis were examined in transgenic rice plants overexpressing the gene encoding cpTPI. The amounts of cpTPI protein in the two lines of transgenic plants were 4.8- and 12.1-folds higher than in wild-type plants, respectively. The magnitude of the increase approximately corresponded to the increase in transcript levels of cpTPI. A at CO2 levels of 100 and 120 Pa increased by 6-9% in the transgenic plants, whereas those at ambient and low CO2 levels were scarcely affected. Similar increases were observed for TPU capacity estimated from the CO2 response curves of A. These results indicate that the overexpression of cpTPI marginally improved photosynthesis at elevated CO2 levels via improvement in TPU capacity in rice. However, biomass production at a CO2 level of 120 Pa did not increase in transgenic plants, suggesting that the improvement in photosynthesis by cpTPI overexpression was not sufficient to improve biomass production in rice.

Revving an Engine of Human Metabolism: Activity Enhancement of Triosephosphate Isomerase via Hemi-Phosphorylation.

Triosephosphate isomerase (TPI) performs the 5th step in glycolysis, operates near the limit of diffusion, and is involved in "moonlighting" functions. Its dimer was found singly phosphorylated at Ser20 (pSer20) in human cells, with this post-translational modification (PTM) showing context-dependent stoichiometry and loss under oxidative stress. We generated synthetic pSer20 proteoforms using cell-free protein synthesis that showed enhanced TPI activity by 4-fold relative to unmodified TPI. Molecular dynamics simulations show that the phosphorylation enables a channel to form that shuttles substrate into the active site. Refolding, kinetic, and crystallographic analyses of point mutants including S20E/G/Q indicate that hetero-dimerization and subunit asymmetry are key features of TPI. Moreover, characterization of an endogenous human TPI tetramer also implicates tetramerization in enzymatic regulation. S20 is highly conserved across eukaryotic TPI, yet most prokaryotes contain E/D at this site, suggesting that phosphorylation of human TPI evolved a new switch to optionally boost an already fast enzyme. Overall, complete characterization of TPI shows how endogenous proteoform discovery can prioritize functional versus bystander PTMs.

Osteoblasts induce glucose-derived ATP perturbations in chondrocytes through noncontact communication.

Cartilage and subchondral bone communicate with each other through material and signal exchanges. However, direct evidence provided by experimental studies on their interactions is insufficient. In the present study, we establish a noncontact co-culture model with a transwell chamber to explore the energetic perturbations in chondrocytes influenced by osteoblasts. Our results indicate that osteoblasts induce more ATP generation in chondrocytes through an energetic shift characterized by enhanced glycolysis and impaired mitochondrial tricarboxylic acid cycle. Enhanced glycolysis is shown by an increase of secreted lactate and the upregulation of glycolytic enzymes, including glucose-6-phosphate isomerase (Gpi), liver type ATP-dependent 6-phosphofructokinase (Pfkl), fructose-bisphosphate aldolase C (Aldoc), glyceraldehyde-3-phosphate dehydrogenase (Gapdh), triosephosphate isomerase (Tpi1), and phosphoglycerate kinase 1 (Pgk1). Impaired mitochondrial tricarboxylic acid cycle is characterized by the downregulation of cytoplasmic aspartate aminotransferase (Got1) and mitochondrial citrate synthase (Cs). Osteoblasts induce the activation of Akt and P38 signaling to mediate ATP perturbations in chondrocytes. This study may deepen our understanding of the maintenance of metabolic homeostasis in the bone-cartilage unit.

Hidden biochemical fossils reveal an evolutionary trajectory for glycolysis in the prebiotic era.

Glycolysis is present in nearly all organisms alive today. This article proposes an evolutionary trajectory for the development of glycolysis in the framework of the chemoautotrophic theory for the origin of life. In the proposal, trioses and triose-phosphates were appointed to starting points. The six-carbon and the three-carbon intermediates developed in the direction of gluconeogenesis and glycolysis, respectively, differing from the from-bottom-to-up development of enzymatic glycolysis. The examination of enzymatic reaction mechanisms revealed that the enzymes incorporated chemical mechanisms of the nonenzymatic stage, making possible to identify kinship between glyoxalases and glyceraldehyde 3-phosphate dehydrogenase as well as methylglyoxal synthase and triose-phosphate isomerase. This developmental trajectory may shed light on how glycolysis might have developed in the nonenzymatic era.

Characterization and evaluation of a new triosephosphate isomerase homologue from Haemaphysalis longicornis as a candidate vaccine against tick infection.

Haemaphysalis longicornis is an obligate hematophagous ectoparasite that transmits a variety of pathogens causing life­threatening diseases in humans and animals. Triosephosphate isomerase (TIM) is a key enzyme in glycometabolism, making in an interesting anti-tick vaccine candidate antigen. In this study, the open reading frame (ORF) of the TIM homologue from H. longicornis (HlTIM) was shown to consist of 747 bp encoding a protein of 248 amino acids. HlTIM gene expression was detected in all developmental stages and in all tissues of the unfed female tick by quantitative real-time PCR. The HlTIM gene was cloned and inserted into pET-32a (+) to obtain the recombinant HlTIM protein (rHlTIM) and its immunogenicity was confirmed by Western blot. ELISA results showed that rabbits immunized with rHlTIM produced a humoral immune response. A vaccine trial in rabbits against H. longicornis infestation demonstrated that the engorgement weight, oviposition and hatchability of ticks from the rH1TIM group was decreased by 8.6%, 35.4% and 17.3% respectively, compared to the histidine-tagged thioredoxin (Trx) control group. Considering the cumulative effect of vaccination on the evaluated parameters, results showed 50.9% efficacy in the rHlTIM group. The data reported here demonstrate that rHlTIM has potential for further development of a new candidate vaccine for tick control.

Expression of vimentin, TPI and MAT2A in human dermal microvascular endothelial cells during angiogenesis in vitro.

INTRODUCTION: In vitro assays of angiogenesis face immense problems considering their reproducibility based on the inhomogeneous characters of endothelial cells (ECs). It is necessary to detect influencing factors, which affect the angiogenic potency of ECs. OBJECTIVE: This study aimed to analyse expression profiles of vimentin (VIM), triosephosphate isomerase (TPI) and adenosylmethionine synthetase isoform type-2 (MAT2A) during the whole angiogenic cascade in vitro. Furthermore, the impact of knocking down vimentin (VIM) on angiogenesis in vitro was evaluated, while monitoring TPI and MAT2A expression. METHODS: A long-term cultivation and angiogenic stimulation of human dermal microvascular ECs was performed. Cells were characterized via VEGFR-1 and VEGFR-2 expression and a shRNA-mediated knockdown of VIM was performed. The process of angiogenesis in vitro was quantified via morphological staging and mRNA-and protein-levels of all proteins were analysed. RESULTS: While native cells ran through the angiogenic cascade chronologically, knockdown cells only entered beginning stages of angiogenesis and died eventually. Cell cultures showing a higher VEGFR-1 expression survived exclusively and displayed an upregulation of MAT2A and TPI expression. Native cells highly expressed VIM in early stages, MAT2A mainly in the beginning and TPI during the course of angiogenesis in vitro. CONCLUSION: VIM knockdown led to a deceleration of angiogenesis in vitro and knockdown cells displayed expressional changes in TPI and MAT2A. Cell populations with a higher number of stalk cells emerged as being more stable against manipulations and native expression profiles provided an indication of VIM and MAT2A being relevant predominantly in beginning stages and TPI during the whole angiogenic cascade in vitro.

Triosephosphate isomerase of Streptococcus pneumoniae is released extracellularly by autolysis and binds to host plasminogen to promote its activation.

Recruitment of plasminogen is an important infection strategy of the human pathogen Streptococcus pneumoniae to invade host tissues. In Streptococcus aureus, triosephosphate isomerase (TPI) has been reported to bind plasminogen. In this study, the TPI of S. pneumoniae (TpiA) was identified through proteomic analysis of bronchoalveolar lavage fluid from a murine pneumococcal pneumonia model. The binding kinetics of recombinant pneumococcal TpiA with plasminogen were characterized using surface plasmon resonance (SPR, Biacore), ligand blot analyses, and enzyme-linked immunosorbent assay. Enhanced plasminogen activation and subsequent degradation by plasmin were also shown. Release of TpiA into the culture medium was observed to be dependent on autolysin. These findings suggest that S. pneumoniae releases TpiA via autolysis, which then binds to plasminogen and promotes its activation, thereby contributing to tissue invasion via degradation of the extracellular matrix.

Naturally occurring deamidated triosephosphate isomerase is a promising target for cell-selective therapy in cancer.

Human triosephosphate isomerase (HsTIM) is a central glycolytic enzyme and is overexpressed in cancer cells with accelerated glycolysis. Triple-negative breast cancer is highly dependent on glycolysis and is typically treated with a combination of surgery, radiation therapy, and chemotherapy. Deamidated HsTIM was recently proposed as a druggable target. Although thiol-reactive drugs affect cell growth in deamidated HsTIM-complemented cells, the role of this protein as a selective target has not been demonstrated. To delve into the usefulness of deamidated HsTIM as a selective target, we assessed its natural accumulation in breast cancer cells. We found that deamidated HsTIM accumulates in breast cancer cells but not in noncancerous cells. The cancer cells are selectively programmed to undergo cell death with thiol-reactive drugs that induced the production of methylglyoxal (MGO) and advanced glycation-end products (AGEs). In vivo, a thiol-reactive drug effectively inhibits the growth of xenograft tumors with an underlying mechanism involving deamidated HsTIM. Our findings demonstrate the usefulness of deamidated HsTIM as target to develop new therapeutic strategies for the treatment of cancers and other pathologies in which this post translationally modified protein accumulates.

Elevated nuclear localization of glycolytic enzyme TPI1 promotes lung adenocarcinoma and enhances chemoresistance.

Increased glycolysis is a hallmark of tumor, which can provide tumor cells with energy and building blocks to promote cell proliferation. Recent studies have shown that not only the expression of glycolytic genes but also their subcellular localization undergoes a variety of changes to promote development of different types of tumors. In this study, we performed a comprehensive analysis of glycolysis and gluconeogenesis genes based on data from TCGA to identify those with significant tumor-promoting potential across 14 types of tumors. This analysis not only confirms genes that are known to be involved in tumorigenesis, but also reveals a significant correlation of triosephosphate isomerase 1 (TPI1) with poor prognosis, especially in lung adenocarcinoma (LUAD). TPI1 is a glycolytic enzyme that interconverts dihydroxyacetone phosphate (DHAP) to glyceraldehyde 3-phosphate (GAP). We confirm the upregulation of TPI1 expression in clinical LUAD samples and an inverse correlation with the overall patient survival. Knocking down of TPI1 in lung cancer cells significantly reduced cell migration, colony formation, and xenograft tumor growth. Surprisingly, we found that the oncogenic function of TPI1 depends on its translocation to cell nucleus rather than its catalytic activity. Significant accumulation of TPI1 in cell nucleus was observed in LUAD tumor tissues compared with the cytoplasm localization in adjacent normal tissues. Moreover, nuclear translocation of TPI1 is induced by extracellular stress (such as chemotherapy agents and peroxide), which facilitates the chemoresistance of cancer cells. Our study uncovers a novel function of the glycolytic enzyme TPI1 in the LUAD.

Systemic Analyses of the Expression of TPI1 and Its Associations with Tumor Microenvironment in Lung Adenocarcinoma and Squamous Cell Carcinoma.

BACKGROUND: Recent studies have shown that the expression level of triosephosphate isomerase 1 (TPI1) may be associated with the occurrence and metastasis of tumors, but the expression level of TPI1 and its effect on lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) are not yet clear. METHODS: We comprehensively explored and validated the TPI1 expression in lung adenocarcinoma and lung squamous cell carcinoma in public datasets. The associations of TPI1 expression with clinicopathological characteristics and prognosis were also studied in both histological types. Moreover, we analyzed the potential relations of TPI1 with immunomodulators and immune cell infiltrations in the tumor microenvironment based on previous literatures and bioinformatic tools. RESULTS: We found that TPI1 was significantly overexpressed in LUAD and LUSC. Significant associations of TPI1 expression were observed regarding age, gender, and pathological stages in LUAD. However, similar trend was only found with respect to age in LUSC. The high expression of TPI1 was significantly associated with worse survival in LUAD, but not in LUSC. Furthermore, we explored the potential distribution and changes of TPI1 expression in tumor microenvironment. Pathway enrichment analyses were performed to identify possible roles of TPI1 in both lung cancers. CONCLUSIONS: TPI1 was overexpressed in both LUAD and LUSC. Increased TPI1 expression was correlated with poor prognosis in LUAD and changed immune cell infiltrating in various degrees in both histological types. Our study provides insights in understanding the potential roles of TPI1 in tumor progression and immune microenvironment.