Translationally controlled tumor protein interacts with the third cytoplasmic domain of Na,K-ATPase alpha subunit and inhibits the pump activity in HeLa cells

The multifaceted potential of TPT1 as biomarker and therapeutic target

Tumor Protein Translationally-Controlled 1 (TPT1) is a highly conserved gene found across eukaryotic species. The protein encoded by TPT1 is ubiquitously expressed both intracellularly and extracellularly across various tissues, and its levels are influenced by various external factors. TPT1 interacts with several key proteins, including p53, MCL1, and immunoglobulins, highlighting its crucial role in cellular processes. The dysregulation of TPT1 expression has been documented in a wide range of diseases, indicating its potential as a valuable biomarker. Additionally, targeting TPT1 presents a promising approach for treating and preventing various conditions. This review will assess the potential of TPT1 as a biomarker and evaluate the effectiveness of current strategies designed to inhibit TPT1 in disease contexts.

Therapeutic efficacy of JEW-M449, an anti-TCTP monoclonal antibody, administered via the nasal route in a BALB/c mouse model of ovalbumin-induced acute asthma

Numerous studies have highlighted the role of translationally controlled tumor protein (TCTP) as a key inflammatory mediator of asthma and allergies. Our previous study revealed that blocking the cytokine-like activity of TCTP using JEW-M449, an anti-TCTP monoclonal antibody (mAb), alleviated allergic inflammation in asthmatic mice. This study aimed to determine whether directly delivering JEW-M449 into the respiratory tract is a more effective way of mitigating airway inflammation in a mouse model of ovalbumin (OVA)-induced allergic airway inflammation than delivering this antibody via the intraperitoneal (IP) route. OVA-sensitized mice were intranasally administered JEW-M449 to enable its direct delivery to the respiratory tract before OVA challenge. We evaluated the changes in the levels of bronchoalveolar lavage fluid (BALF) cells, T helper type 2 (Th2) cytokines, OVA-specific immunoglobulin E (IgE), and histopathological alterations in the lung tissues. Intranasal (IN) administration of JEW-M449 significantly ameliorated the pathological changes associated with OVA-induced lung injury, including reduced inflammatory cell infiltration and mucus hypersecretion. Mice IN administered JEW-M449 also showed decreased OVA-mediated induction of Th2 cytokines in BALF and lung homogenates. Importantly, JEW-M449 delivered via the IN route reached the lung tissue more effectively and exerted superior anti-inflammatory effects in OVA-challenged mice than the IP-delivered JEW-M449. This study is the first to demonstrate the efficacy of directly delivering JEW-M449 anti-TCTP mAb into the respiratory tract to alleviate the asthma phenotype in a mouse model, thereby highlighting a potential delivery strategy for novel inhaled mAb therapeutics for human asthma.

Targeting the translationally controlled tumor protein by a monoclonal antibody improves allergic airway inflammation in mice

Secretion of translationally controlled tumor protein (TCTP) was found in body fluids during the late phase of allergic reactions, implicating TCTP in allergic diseases. Furthermore, blocking TCTP has been shown to be helpful in treating asthma and allergies in animal models. The objectives of this study were to produce anti-TCTP monoclonal antibodies (mAbs), test their ability to inhibit the cytokine-like function of dimeric TCTP (dTCTP) in vitro and to assess their therapeutic effects in a murine model of ovalbumin (OVA)-induced airway inflammation. We first verified the inhibitory effects of 4 anti-TCTP mAbs on dTCTP-induced secretion of IL-8 in BEAS-2B cells. To investigate the anti-inflammatory effect of anti-TCTP mAbs on allergic airway inflammation, we treated OVA-sensitized mice with anti-TCTP mAbs before OVA challenge. The changes in bronchoalveolar lavage fluid (BALF) cells, IL-4, IL-5, and IL-13 levels in both BALF and lung homogenates, plasma levels of OVA-specific IgE, and lung tissues were analyzed. We found that JEW-M449 anti-TCTP mAb bound to the flexible loop of TCTP and significantly inhibited dTCTP-induced IL-8 release, making it the most effective inhibitor in our study. We also found that treatment with JEW-M449 significantly reduced the infiltration of inflammatory cells and suppressed the OVA-induced upregulation of type 2 cytokines in both BALF and lung homogenates in a dose-dependent manner. In addition, JEW-M449 significantly attenuated the degree of goblet cell hyperplasia and mucus secretion. Our results demonstrate that specific targeting of the flexible loop of TCTP is a potent strategy for treating airway inflammatory diseases.

Translationally controlled tumor protein restores impaired memory and altered synaptic protein expression in animal models of dementia

This study describes the effects of translationally controlled tumor protein (TCTP) on mice with memory impairment caused by scopolamine (SCO) administration. Specifically, memory functions and expression levels of hippocampal synaptic proteins in 7- to 12-month-old SCO-treated wild-type (WT-SCO) mice were compared to those of TCTP-overexpressing (TG) and TCTP knocked-down (KD) mice similarly treated with SCO. Passive-avoidance tasks were performed with WT, TG, and KD mice for four weeks after intraperitoneal injection of SCO or saline followed by an acquisition test. After completing behavioral studies, hippocampi of all mice groups were collected and their synaptic protein contents were subjected to Western blotting or immunohistochemical analyses, and compared with those of 5x familial Alzheimer's disease (5xFAD) mice and postmortem AD patients. Results of passive avoidance tests revealed that SCO-induced memory impairment was repaired in TCTP-TG mice, but not in TCTP-KD mice. Hippocampal expression levels of synaptophysin, synapsin-1, and PSD-95 were increased in TCTP-TG mice treated with SCO (TG-SCO) but decreased in TCTP-KD mice treated with SCO (KD-SCO). Decreased levels of TCTP, synaptophysin, and PSD-95 were also found in hippocampi of 5xFAD mice and AD patients. Expression levels of p-CREB/CREB and brain-derived neurotrophic factor (BDNF) in TCTP-TG and TG-SCO mice were similar to or increased compared to those in WT mice, but decreased in TCTP-KD and KD-SCO mice. BDNF immunoreactivity was restored in CA1 regions of hippocampi of TG-SCO mice, but not in KD-SCO mice. These results suggest that TCTP can restore damaged memory in mice possibly through restored synaptic protein expression.

PEGylation improves the therapeutic potential of dimerized translationally controlled tumor protein blocking peptide in ovalbumin-induced mouse model of airway inflammation

Dimerized translationally controlled tumor protein (dTCTP) initiates a variety of allergic responses in mouse models and that dTCTP-binding peptide 2 (dTBP2) attenuates the allergic inflammation by targeting dTCTP. However, the usefulness of peptide-based drugs is often limited due to their short half-lives, rapid degradation, and high levels of clearance after systemic administration. In this study, we chemically conjugated dTBP2 with 10 kDa polyethylene glycol (PEG) to improve its therapeutic potential. N-terminal mono-PEGylated dTBP2 (PEG-dTBP2) was characterized by in vitro bioactivity assay, pharmacokinetics study, and in vivo efficacy. When compared to the unmodified dTBP2, PEG-dTBP2 reduced proinflammatory cytokine IL-8 secretion in human bronchial cells by 10 to 15% and increased plasma half-life by approximately 2.5-fold in mice. This study specifically demonstrated that PEG-dTBP2 shows higher inhibitory action against ovalbumin (OVA)-induced airway inflammation in mice compared to dTBP2. Importantly, PEG-dTBP2, when administered once at 1 mg/kg, significantly reduced the migration of inflammatory cells and the levels of cytokines in the bronchoalveolar lavage fluids as well as OVA-specific IgE levels in serum. In addition, the degree of goblet cell hyperplasia and mucus secretion were significantly attenuated in the PEG-dTBP2 group compared with the control group. These results suggest that PEG-dTBP2 can be considered a potential candidate drug for regulating allergic inflammation.

Role of Translationally Controlled Tumor Protein (TCTP) in the Development of Hypertension and Related Diseases in Mouse Models

Translationally controlled tumor protein (TCTP) is a multifunctional protein that plays a wide variety of physiological and pathological roles, including as a cytoplasmic repressor of Na,K-ATPase, an enzyme pivotal in maintaining Na+ and K+ ion gradients across the plasma membrane, by binding to and inhibiting Na,K-ATPase. Studies with transgenic mice overexpressing TCTP (TCTP-TG) revealed the pathophysiological significance of TCTP in the development of systemic arterial hypertension. Overexpression of TCTP and inhibition of Na,K-ATPase result in the elevation of cytoplasmic Ca2+ levels, which increases the vascular contractility in the mice, leading to hypertension. Furthermore, studies using an animal model constructed by multiple mating of TCTP-TG with apolipoprotein E knockout mice (ApoE KO) indicated that TCTP-induced hypertension facilitates the severity of atherosclerotic lesions in vivo. This review attempts to discuss the mechanisms underlying TCTP-induced hypertension and related diseases gleaned from studies using genetically altered animal models and the potential of TCTP as a target in the therapy of hypertension-related pathological conditions.

SUMOylation of Translationally Regulated Tumor Protein Modulates Its Immune Function

Translationally controlled tumor protein (TCTP) is a highly conserved protein possessing numerous biological functions and molecular interactions, ranging from cell growth to immune responses. However, the molecular mechanism by which TCTP regulates immune function is largely unknown. Here, we found that knockdown of Bombyx mori translationally controlled tumor protein (BmTCTP) led to the increased susceptibility of silkworm cells to virus infection, whereas overexpression of BmTCTP significantly decreased the virus replication. We further demonstrated that BmTCTP could be modified by SUMOylation molecular BmSMT3 at the lysine 164 via the conjugating enzyme BmUBC9, and the stable SUMOylation of BmTCTP by expressing BmTCTP-BmSMT3 fusion protein exhibited strong antiviral activity, which confirmed that the SUMOylation of BmTCTP would contribute to its immune responses. Further work indicated that BmTCTP is able to physically interact with interleukin enhancer binding factor (ILF), one immune molecular, involved in antivirus, and also induce the expression of BmILF in response to virus infection, which in turn enhanced antiviral activity of BmTCTP. Altogether, our present study has provided a novel insight into defending against virus via BmTCTP SUMOylation signaling pathway and interacting with key immune molecular in silkworm.

Regulation of epithelial integrity and organ growth by Tctp and Coracle in Drosophila

Regulation of cell junctions is crucial for the integrity of epithelial tissues and organs. Cell junctions also play roles in controlling cell proliferation for organ growth. Translationally controlled tumor protein (TCTP) is a conserved protein involved in growth control, but its role in cell junctions is unknown. Here we show that Drosophila Tctp directly interacts with the septate junction protein Coracle (Cora) to regulate epithelial integrity and organ growth. Tctp localizes together with Cora in the epidermis of the embryo. Loss of Cora reduces the level of Tctp in the epidermis but not vice versa. cora/+ or Tctp/+ single heterozygotes develop normally to adulthood. However, double heterozygotes for cora and Tctp mutations show severe disruption of epithelia causing synthetic lethality in the embryo. Double knockdown of Cora and Tctp in eye imaginal disc synergistically leads to disruption of the eye disc, resulting in a severe reduction or loss of eye and head. Conversely, double knockdown of Cora and Tctp in wing disc causes overgrowth as well as cell death. Inhibition of cell death under this condition causes hyperplastic growth of the wing disc. Tctp also shows direct and functional interaction with Cora-associated factors like Yurt and Na⁺/K⁺-ATPase. This study suggests that proper levels of Tctp and Cora are essential for the maintenance of the Cora complex and the integrity of epithelia. Our data also provide evidence that both Cora and Tctp are required to suppress overgrowth in developing wing.

Organ growth depends on intercellular signaling for cell proliferation. Accumulating evidence indicates that tissue growth is also regulated by cell junctions. Translationally controlled tumor protein (TCTP) is an evolutionarily conserved protein family implicated in cancer. In Drosophila, Tctp is required for diverse cytoplasmic and nuclear functions including organ growth, DNA repair, and chromatin regulation during development. However, it is unknown whether Tctp plays an additional role in cell junctions at the membrane. Here we show that Tctp localizes together with the FERM domain protein Coracle (Cora) at the basolateral septate junctions in some tissues. Our data suggest that Cora is required for the maintenance of Tctp in the cell membrane but not vice versa. Tctp forms a complex with Cora, and the mutations in cora and Tctp genes show synergistic genetic interaction in the embryo and developing organs. Remarkably, the reduction of Cora and Tctp can induce massive overgrowth in the wing. We propose that the direct interaction of Tctp with the Cora junction complex is required for epithelial integrity and organ growth during development.

TCTP is Essential for Cell Proliferation and Survival during CNS Development

Translationally controlled tumor-associated protein (TCTP) has been implicated in cell growth, proliferation, and apoptosis through interacting proteins. Although TCTP is expressed abundantly in the mouse brain, little is known regarding its role in the neurogenesis of the nervous system. We used Nestin-cre-driven gene-mutated mice to investigate the function of TCTP in the nervous system. The mice carrying disrupted TCTP in neuronal and glial progenitor cells died at the perinatal stage. The Nestin^Cre/+; TCTP^f/f pups displayed reduced body size at postnatal day 0.5 (P0.5) and a lack of milk in the stomach compared with littermate controls. In addition to decreased cell proliferation, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) and caspase assay revealed that apoptosis was increased in newly committed TCTP-disrupted cells as they migrated away from the ventricular zone. The mechanism may be that the phenotype from specific deletion of TCTP in neural progenitor cells is correlated with the decreased expression of cyclins D2, E2, Mcl-1, Bcl-xL, hax-1, and Octamer-binding transcription factor 4 (Oct4) in conditional knockout mice. Our results demonstrate that TCTP is a critical protein for cell survival during early neuronal and glial differentiation. Thus, enhanced neuronal loss and functional defect in Tuj1 and doublecortin-positive neurons mediated through increased apoptosis and decreased proliferation during central nervous system (CNS) development may contribute to the perinatal death of TCTP mutant mice.

Analysis of translation control tumor protein related to deltamethrin stress in Drosophila kc cells

The translation control tumor protein (TCTP) is a kind of conservative, common and important molecule, several functions (such as regulating cell cycle, apoptosis and calcium binding) have been reported. However, few academic researches for role of TCTP in insecticides stress were made so far. In this research, Drosophila kc cells treated with different doses of deltamethrin at different times, indicated that the expression of TCTP reached the highest level when the cells were treated with 20 ppm of deltamethrin at 24 h. The results showed that TCTP expression is associated with deltamethrin stress. To investigate the functional relationship between this gene and deltamethrin resistance, RNA interference (RNAi) and cell transfection were utilized. TCTP knockdown significantly reduced the level of resistance of RNAi-treated cells, and the overexpressions of TCTP in Drosophila kc cells conferred a degree of protection against deltamethrin. Flow cytometry data showed increased apoptosis rate of RNAi-treated cells and decreased apoptosis following cell transfection. These results represent the first evidence that TCTP plays an important role in the regulation of deltamethrin resistance. Therefore, this study could help us to elucidate the environmental toxicity of deltamethrin and new target genes associated with resistance.

GPR35 promotes glycolysis, proliferation, and oncogenic signaling by engaging with the sodium potassium pump

The sodium potassium pump (Na/K-ATPase) ensures the electrochemical gradient of a cell through an energy-dependent process that consumes about one-third of regenerated ATP. We report that the G protein-coupled receptor GPR35 interacted with the α chain of Na/K-ATPase and promotes its ion transport and Src signaling activity in a ligand-independent manner. Deletion of Gpr35 increased baseline Ca²⁺ to maximal levels and reduced Src activation and overall metabolic activity in macrophages and intestinal epithelial cells (IECs). In contrast, a common T108M polymorphism in GPR35 was hypermorphic and had the opposite effects to Gpr35 deletion on Src activation and metabolic activity. The T108M polymorphism is associated with ulcerative colitis and primary sclerosing cholangitis, inflammatory diseases with a high cancer risk. GPR35 promoted homeostatic IEC turnover, whereas Gpr35 deletion or inhibition by a selective pepducin prevented inflammation-associated and spontaneous intestinal tumorigenesis in mice. Thus, GPR35 acts as a central signaling and metabolic pacesetter, which reveals an unexpected role of Na/K-ATPase in macrophage and IEC biology.

Identification of phosphorylation proteins in response to water deficit during wheat flag leaf and grain development

BACKGROUND

Wheat (Triticum aestivum L.) serves as important grain crop widely cultivated in the world, which is often suffered by drought stress in natural conditions. As one of the most important post translation modifications, protein phosphorylation widely participates in plant abiotic stress regulation. In this study, we performed the first comparative analysis of phosphorylated protein characterization in flag leaves and developing grains of elite Chinese bread wheat cultivar Zhongmai 175 under water deficit by combining with proteomic approach and Pro-Q Diamond gel staining.

RESULTS

Field experiment showed that water deficit caused significant reduction of plant height, tiller number, ear length and grain yield. 2-DE and Pro-Q Diamond gel staining analysis showed that 58 proteins were phosphorylated among 112 differentially accumulated proteins in response to water deficit, including 20 in the flag leaves and 38 in the developing grains. The phosphorylated proteins from flag leaves mainly involved in photosynthesis, carbohydrate and energy metabolism, while those from developing grains were closely related with detoxification and defense, protein, carbohydrate and energy metabolism. Particularly, water deficit resulted in significant downregulation of phosphorylated modification level in the flag leaves, which could affect photosynthesis and grain yield. However, some important phosphorylated proteins involved in stress defense, energy metabolism and starch biosynthesis were upregulated under water deficit, which could benefit drought tolerance, accelerate grain filling and shorten grain developing time.

CONCLUSIONS

The modification level of those identified proteins from flag leaves and grains had great changes when wheat was suffered from water deficit, indicating that phosphoproteins played a key role in response to drought stress. Our results provide new insights into the molecular mechanisms how phosphoproteins respond to drought stress and thus reduce production.

The translationally controlled tumor protein TCTP is involved in cell cycle progression and heat stress response in the bloodstream form of Trypanosoma brucei

The translationally controlled tumor protein TCTP, is a universally conserved protein that seems to be of essential function in all systems tested so far. TCTP is involved in a multitude of cellular functions including cell cycle control, cell division, apoptosis and many more. The mechanism of how TCTP is involved in most of these functions remains elusive. Here we describe that TCTP is a cytoplasmic protein involved in cell cycle regulation and heat stress response in the bloodstream form of Trypanosoma brucei.

Some Biological Consequences of the Inhibition of Na,K-ATPase by Translationally Controlled Tumor Protein (TCTP)

Na,K-ATPase is an ionic pump that regulates the osmotic equilibrium and membrane potential of cells and also functions as a signal transducer. The interaction of Na,K-ATPase with translationally controlled tumor protein (TCTP) results, among others, in the inhibition of the former's pump activity and in the initiation of manifold biological and pathological phenomena. These phenomena include hypertension and cataract development in TCTP-overexpressing transgenic mice, as well as the induction of tumorigenesis signaling pathways and the activation of Src that ultimately leads to cell proliferation and migration. This review attempts to collate the biological effects of Na,K-ATPase and TCTP interaction and suggests that this interaction has the potential to serve as a possible therapeutic target for selected diseases.

Distinct 3' UTRs regulate the life-cycle-specific expression of two TCTP paralogs in Trypanosoma brucei

The translationally controlled tumor protein (TCTP; also known as TPT1 in mammals) is highly conserved and ubiquitously expressed in eukaryotes. It is involved in growth and development, cell cycle progression, protection against cellular stresses and apoptosis, indicating the multifunctional role of the protein. Here, for the first time, we characterize the expression and function of TCTP in the human and animal pathogen, Trypanosoma brucei. We identified two paralogs (TCTP1 and TCTP2) that are differentially expressed in the life cycle of the parasite. The genes have identical 5′ untranslated regions (UTRs) and almost identical open-reading frames. The 3′UTRs differ substantially in sequence and length, and are sufficient for the exclusive expression of TCTP1 in procyclic- and TCTP2 in bloodstream-form parasites. Furthermore, we characterize which parts of the 3′UTR are needed for TCTP2 mRNA stability. RNAi experiments demonstrate that TCTP1 and TCTP2 expression is essential for normal cell growth in procyclic- and bloodstream-form parasites, respectively. Depletion of TCTP1 in the procyclic form cells leads to aberrant cell and mitochondrial organelle morphology, as well as enlarged, and a reduced number of, acidocalcisomes.

Summary:T. brucei has two TCTP genes that are differentially expressed during the parasite life cycle owing to their different 3′UTRs. TCTP also has a role in regulating cell growth and morphology.

Dehydrocostus lactone, a sesquiterpene from Saussurea lappa Clarke, suppresses allergic airway inflammation by binding to dimerized translationally controlled tumor protein

BACKGROUND

We previously reported that the biologically active form of histamine releasing factor (HRF) is dimerized translationally controlled tumor protein (dTCTP) which is involved in a number of allergic diseases.

HYPOTHESIS/PURPOSE

Hoping that agents that modulate dTCTP may provide new therapeutic targets to allergic inflammatory diseases, we screened a library of natural products for substances that inhibit dTCTP. One such inhibitor we found was dehydrocostus lactone (DCL), a natural sesquiterpene present in rhizome of Saussurea lappa Clarke, the subject of this study.

METHODS

We evaluated the therapeutic efficacy of DCL in a mouse model of ovalbumin (OVA)-induced allergic airway inflammation, employing the ELISA system using BEAS-2B cells and splenocytes, and confirmed that DCL interacts with dTCTP using SPR assay.

RESULTS

DCL inhibited dTCTP-induced secretion of IL-8 in BEAS-2B cells. From kinetic analysis of dTCTP and DCL, we found that K_D value was 5.33 ± 0.03 μM between dTCTP and DCL. DCL also significantly reduced inflammatory lung eosinophilia, type 2 cytokines in BALF, as well as OVA specific IgE and mucus production in a mouse model of ovalbumin induced allergy. Moreover, DCL suppressed NF-κB activation.

CONCLUSION

DCL's therapeutic potential in allergic airway inflammation is based on its anti-inflammatory activity of suppressing the function of dTCTP.

Identification of translationally controlled tumor protein in promotion of DNA homologous recombination repair in cancer cells by affinity proteomics

Translationally controlled tumor protein(TCTP) has been implicated in the regulation of apoptosis, DNA repair and drug resistance. However, the underlying molecular mechanisms are poorly defined. To better understand the molecular mechanisms underlying TCTP involved in cellular processes, we performed an affinity purification-based proteomic profiling to identify proteins interacting with TCTP in human cervical cancer HeLa cells. We found that a group of proteins involved in DNA repair are enriched in the potential TCTP interactome. Silencing TCTP by short hairpin RNA in breast carcinoma MCF-7 cells leads to the declined repair efficiency for DNA double-strand breaks on the GFP-Pem1 reporter gene by homologous recombination, the persistent activation and the prolonged retention of γH2AX and Rad51 foci following ionizing radiation. Reciprocal immunoprecipitations indicated that TCTP forms complexes with Rad51 in vivo, and the stability maintenance of Rad51 requires TCTP in MCF-7 cells under normal cell culture conditions. Moreover, inactivation of TCTP by sertraline treatment enhances UVC irradiation-induced apoptosis in MCF-7 cells, and causes sensitization to DNA-damaging drug etoposide and DNA repair inhibitor olaparib. Thus, we have identified an important role of TCTP in promoting DNA double-stand break repair via facilitating DNA homologous recombination processes and highlighted the great potential of TCTP as a drug target to enhance conventional chemotherapy for cancer patients with high levels of TCTP expression.

Fortilin: A Potential Target for the Prevention and Treatment of Human Diseases

Fortilin is a highly conserved 172-amino-acid polypeptide found in the cytosol, nucleus, mitochondria, extracellular space, and circulating blood. It is a multifunctional protein that protects cells against apoptosis, promotes cell growth and cell cycle progression, binds calcium (Ca²⁺) and has antipathogen activities. Its role in the pathogenesis of human and animal diseases is also diverse. Fortilin facilitates the development of atherosclerosis, contributes to both systemic and pulmonary arterial hypertension, participates in the development of cancers, and worsens diabetic nephropathy. It is important for the adaptive expansion of pancreatic β-cells in response to obesity and increased insulin requirement, for the regeneration of liver after hepatectomy, and for protection of the liver against alcohol- and ER stress-induced injury. Fortilin is a viable surrogate marker for in vivo apoptosis, and it plays a key role in embryo and organ development in vertebrates. In fish and shrimp, fortilin participates in host defense against bacterial and viral pathogens. Further translational research could prove fortilin to be a viable molecular target for treatment of various human diseases including and not limited to atherosclerosis, hypertension, certain tumors, diabetes mellitus, diabetic nephropathy, hepatic injury, and aberrant immunity and host defense.

Function of translationally controlled tumor protein (TCTP) in Eudrilus eugeniae regeneration

TCTP (Translationally Controlled Tumour Protein) is a multifunctional protein that plays a role in the development, immune system, tumour reversion, and maintenance of stem cells. The mRNA of the Tpt1 gene is over-expressed during liver regeneration. But, the function of the protein in regeneration is not known. To study the role of the protein in regeneration, the earthworm Eudrilus eugeniae was chosen. First, the full length cDNA of the Tpt1 gene was sequenced. The size of the cDNA is 504 bp and the protein has 167 amino acids. The highest level of TCTP expression was documented in the worm after three days of regeneration. The protein was found to be expressed specifically in the epithelial layer of the skin. During regeneration, the protein expression was found to be the highest at the tip of blastema. The pharmacological suppression of TCTP using nutlin-3 and TCTP RNAi experiments resulted in the failure of the regeneration process. The suppression of TCTP caused the arrest of proliferation in posterior amputated worms. The severe cell death was documented in the amputated region of nutlin-3 injected worm. The silencing of TCTP has blocked the modification of clitellar segments. The experiments confirm that TCTP has major functions in the upstream signalling of cell proliferation in the early regeneration process in E. eugeniae.

Immunohistochemical Localization of Translationally Controlled Tumor Protein in Axon Terminals of Mouse Hippocampal Neurons

Translationally controlled tumor protein (TCTP) is a cytosolic protein with microtubule stabilization and calcium-binding activities. TCTP is expressed in most organs including the nervous system. However, detailed distribution and functional significance of TCTP in the brain remain unexplored. In this study, we investigated the global and subcellular distributions of TCTP in the mouse brain. Immunohistochemical analyses with anti-TCTP revealed that TCTP was widely distributed in almost all regions of the brain including the cerebral cortex, thalamus, hypothalamus, hippocampus, and amygdala, wherein it was localized in axon tracts and axon terminals. In the hippocampus, TCTP was prominently localized to axon terminals of the perforant path in the dentate gyrus, the mossy fibers in the cornu ammonis (CA)3 region, and the Schaffer collaterals in the CA1 field, but not in cell bodies of granule cells and pyramidal neurons, and in their dendritic processes. Widespread distribution of TCTP in axon tracts and axon terminals throughout the brain suggests that TCTP is likely involved in neurotransmitter release and/or maintaining synaptic structures in the brain, and that it might have a role in maintaining synaptic functions and synaptic configurations important for normal cognitive, stress and emotional functions.

Structural Insights into TCTP and Its Interactions with Ligands and Proteins

The 19-24 kDa Translationally Controlled Tumor Protein (TCTP) is involved in a wide range of molecular interactions with biological and nonbiological partners of various chemical compositions such as proteins, peptides, nucleic acids, carbohydrates, or small molecules. TCTP is therefore an important and versatile binding platform. Many of these protein-protein interactions have been validated, albeit only few received an in-depth structural characterization. In this chapter, we will focus on the structural analysis of TCTP and we will review the available literature regarding its interaction network from a structural perspective.

The Translational Controlled Tumour Protein TCTP: Biological Functions and Regulation

The Translational Controlled Tumour Protein TCTP (gene symbol TPT1, also called P21, P23, Q23, fortilin or histamine-releasing factor, HRF) is a highly conserved protein present in essentially all eukaryotic organisms and involved in many fundamental cell biological and disease processes. It was first discovered about 35 years ago, and it took an extended period of time for its multiple functions to be revealed, and even today we do not yet fully understand all the details. Having witnessed most of this history, in this chapter, I give a brief overview and review the current knowledge on the structure, biological functions, disease involvements and cellular regulation of this protein.TCTP is able to interact with a large number of other proteins and is therefore involved in many core cell biological processes, predominantly in the response to cellular stresses, such as oxidative stress, heat shock, genotoxic stress, imbalance of ion metabolism as well as other conditions. Mechanistically, TCTP acts as an anti-apoptotic protein, and it is involved in DNA-damage repair and in cellular autophagy. Thus, broadly speaking, TCTP can be considered a cytoprotective protein. In addition, TCTP facilitates cell division through stabilising the mitotic spindle and cell growth through modulating growth signalling pathways and through its interaction with the proteosynthetic machinery of the cell. Due to its activities, both as an anti-apoptotic protein and in promoting cell growth and division, TCTP is also essential in the early development of both animals and plants.Apart from its involvement in various biological processes at the cellular level, TCTP can also act as an extracellular protein and as such has been involved in modulating whole-body defence processes, namely in the mammalian immune system. Extracellular TCTP, typically in its dimerised form, is able to induce the release of cytokines and other signalling molecules from various types of immune cells. There are also several examples, where TCTP was shown to be involved in antiviral/antibacterial defence in lower animals. In plants, the protein appears to have a protective effect against phytotoxic stresses, such as flooding, draught, too high or low temperature, salt stress or exposure to heavy metals. The finding for the latter stress condition is corroborated by earlier reports that TCTP levels are considerably up-regulated upon exposure of earthworms to high levels of heavy metals.Given the involvement of TCTP in many biological processes aimed at maintaining cellular or whole-body homeostasis, it is not surprising that dysregulation of TCTP levels may promote a range of disease processes, foremost cancer. Indeed a large body of evidence now supports a role of TCTP in at least the most predominant types of human cancers. Typically, this can be ascribed to both the anti-apoptotic activity of the protein and to its function in promoting cell growth and division. However, TCTP also appears to be involved in the later stages of cancer progression, such as invasion and metastasis. Hence, high TCTP levels in tumour tissues are often associated with a poor patient outcome. Due to its multiple roles in cancer progression, TCTP has been proposed as a potential target for the development of new anti-cancer strategies in recent pilot studies. Apart from its role in cancer, TCTP dysregulation has been reported to contribute to certain processes in the development of diabetes, as well as in diseases associated with the cardiovascular system.Since cellular TCTP levels are highly regulated, e.g. in response to cell stress or to growth signalling, and because deregulation of this protein contributes to many disease processes, a detailed understanding of regulatory processes that impinge on TCTP levels is required. The last section of this chapter summarises our current knowledge on the mechanisms that may be involved in the regulation of TCTP levels. Essentially, expression of the TPT1 gene is regulated at both the transcriptional and the translational level, the latter being particularly advantageous when a rapid adjustment of cellular TCTP levels is required, for example in cell stress responses. Other regulatory mechanisms, such as protein stability regulation, may also contribute to the regulation of overall TCTP levels.

Suppression of intestinal immunity through silencing of TCTP by RNAi in transgenic silkworm, Bombyx mori

Intestinal immune response is a front line of host defense. The host factors that participate in intestinal immunity response remain largely unknown. We recently reported that Translationally Controlled Tumor Protein (BmTCTP) was obtained by constructing a phage display cDNA library of the silkworm midgut and carrying out high throughput screening of pathogen binding molecules. To further address the function of BmTCTP in silkworm intestinal immunity, transgenic RNAi silkworms were constructed by microinjection piggBac plasmid to Dazao embryos. The antimicrobial capacity of transgenic silkworm decreased since the expression of gut antimicrobial peptide from transgenic silkworm was not sufficiently induced during oral microbial challenge. Moreover, dynamic ERK phosphorylation from transgenic silkworm midgut was disrupted. Taken together, the innate immunity of intestinal was suppressed through disruption of dynamic ERK phosphorylation after oral microbial infection as a result of RNAi-mediated knockdown of midgut TCTP in transgenic silkworm.

OsTCTP, encoding a translationally controlled tumor protein, plays an important role in mercury tolerance in rice

BACKGROUND

Mercury (Hg) is not only a threat to public health but also a growth risk factor to plants, as it is readily accumulated by higher plants. Accumulation of Hg in plants disrupts many cellular-level functions and inhibits growth and development; however, the detoxification and tolerance mechanisms of plants to Hg stress are still not fully understood. Exposure to toxic Hg also occurs in some crops cultivated under anoxic conditions, such as rice (Oryza sativa L.), a model organism and one of the most important cultivated plants worldwide. In this study, we functionally characterized a rice translationally controlled tumor protein gene (Os11g43900, OsTCTP) involved in Hg stress tolerance.

RESULTS

OsTCTP was ubiquitously expressed in all examined plant tissues, especially in actively dividing and differentiating tissues, such as roots and nodes. OsTCTP was found to localize both the cytosol and the nucleus. OsTCTP was induced by mercuric chloride, cupric sulfate, abscisic acid, and hydrogen peroxide at the protein level in a time-dependent manner. Overexpression of OsTCTP potentiated the activities of several antioxidant enzymes, reduced the Hg-induced H2O2 levels, and promoted Hg tolerance in rice, whereas knockdown of OsTCTP produced opposite effects. And overexpression of OsTCTP did not prevent Hg absorption and accumulation in rice. We also demonstrated that Asn 48 and Asn 97 of OsTCTP amino acids were not the potential N-glycosylation sites.

CONCLUSIONS

Our results suggest that OsTCTP is capable of decreasing the Hg-induced reactive oxygen species (ROS), therefore, reducing the damage of ROS and enhancing the tolerance of rice plants to Hg stress. Thus, OsTCTP is a valuable gene for genetic engineering to improve rice performance under Hg contaminated paddy soils.

Insulin induces phosphorylation of serine residues of translationally controlled tumor protein in 293T cells

Insulin induces the activation of Na,K-ATPase while translationally controlled tumor protein (TCTP) inhibits this enzyme and the associated pump activity. Because binding of insulin with its membrane receptor is known to mediate the phosphorylation of multiple intracellular proteins, phosphorylation of TCTP by insulin might be related to the sodium pump regulation. We therefore examined whether insulin induces TCTP phosphorylation in embryonic kidney 293T cells. Using immunoprecipitation and Western blotting, we found that insulin phosphorylates serine (Ser) residues of TCTP. Following fractionation of the insulin-treated cells into cytosol and membrane fractions, phosphorylated TCTP at its Ser residue (p-Ser-TCTP) was detected exclusively in the cytosolic part and not in the membrane fraction. Phosphorylation of TCTP reached maximum in about 10 min after insulin treatment in 293T cells. In studies of cell-type specificity of insulin-mediated phosphorylation of TCTP, insulin did not phosphorylate TCTP in HeLa cells. Computational prediction and immunoprecipitation using several constructs having Ser to Ala mutation at potential p-Ser sites of TCTP revealed that insulin phosphorylated the serine-9 and -15 residues of TCTP. Elucidations of how insulin-mediated TCTP phosphorylation promotes Na,K-ATPase activation, may offer potential therapeutic approaches to diseases associated with vascular activity and sodium pump dysregulation.

Evolutionarily conserved binding of translationally controlled tumor protein to eukaryotic elongation factor 1B

Translationally controlled tumor protein (TCTP) is an abundant protein that is highly conserved in eukaryotes. However, its primary function is still not clear. Human TCTP interacts with the metazoan-specific eukaryotic elongation factor 1Bδ (eEF1Bδ) and inhibits its guanine nucleotide exchange factor (GEF) activity, but the structural mechanism remains unknown. The interaction between TCTP and eEF1Bδ was investigated by NMR titration, structure determination, paramagnetic relaxation enhancement, site-directed mutagenesis, isothermal titration calorimetry, and HADDOCK docking. We first demonstrated that the catalytic GEF domain of eEF1Bδ is not responsible for binding to TCTP but rather a previously unnoticed central acidic region (CAR) domain in eEF1Bδ. The mutagenesis data and the structural model of the TCTP-eEF1Bδ CAR domain complex revealed the key binding residues. These residues are highly conserved in eukaryotic TCTPs and in eEF1B GEFs, including the eukaryotically conserved eEF1Bα, implying the interaction may be conserved in all eukaryotes. Interactions were confirmed between TCTP and the eEF1Bα CAR domain for human, fission yeast, and unicellular photosynthetic microalgal proteins, suggesting that involvement in protein translation through the conserved interaction with eEF1B represents a primary function of TCTP.

Translationally controlled tumor protein induces epithelial to mesenchymal transition and promotes cell migration, invasion and metastasis

Translationally controlled tumor protein (TCTP), is a highly conserved protein involved in fundamental processes, such as cell proliferation and growth, tumorigenesis, apoptosis, pluripotency, and cell cycle regulation. TCTP also inhibits Na,K-ATPase whose subunits have been suggested as a marker of epithelial-to-mesenchymal transition (EMT), a crucial step during tumor invasiveness, metastasis and fibrosis. We hypothesized that, TCTP might also serve as an EMT inducer. This study attempts to verify this hypothesis. We found that overexpression of TCTP in a porcine renal proximal tubule cell line, LLC-PK1, induced EMT-like phenotypes with the expected morphological changes and appearance of EMT related markers. Conversely, depletion of TCTP reversed the induction of these EMT phenotypes. TCTP overexpression also enhanced cell migration via activation of mTORC2/Akt/GSK3β/β-catenin, and invasiveness by activating MMP-9. Moreover, TCTP depletion in melanoma cells significantly reduced pulmonary metastasis by inhibiting the development of mesenchymal-like phenotypes. Overall, these findings support our hypothesis that TCTP is a positive regulator of EMT and suggest that modulation of TCTP expression is a potential approach to inhibit the invasiveness and migration of cancer cells and the attendant pathologic processes including metastasis.

Up-regulation of Rhoa/Rho kinase pathway by translationally controlled tumor protein in vascular smooth muscle cells

Translationally controlled tumor protein (TCTP), a repressor for Na,K-ATPase has been implicated in the development of systemic hypertension, as proved by TCTP-over-expressing transgenic (TCTP-TG) mice. Aorta of TCTP-TG exhibited hypercontractile response compared to that of non-transgenic mice (NTG) suggesting dys-regulation of signaling pathways involved in the vascular contractility by TCTP. Because dys-regulation of RhoA/Rho kinase pathway is implicated in increased vascular contractility, we examined whether TCTP induces alterations in RhoA pathway in vascular smooth muscle cells (VSMCs). We found that TCTP over-expression by adenovirus infection up-regulated RhoA pathway including the expression of RhoA, and its downstream signalings, phosphorylation of myosin phosphatase target protein (MYPT-1), and myosin light chain (MLC). Conversely, lentiviral silencing of TCTP reduced the RhoA expression and Rho kinase signalings. Using immunohistochemical and Western blotting studies on aortas from TCTP-TG confirmed the elevated expression of RhoA and increase in p-MLC (phosphorylated MLC). In contrast, down-regulation of RhoA and p-MLC were found in aortas from heterozygous mice with deleted allele of TCTP (TCTP^+/−). We conclude that up-regulation of TCTP induces RhoA-mediated pathway, and that TCTP-induced RhoA plays a role in the regulation in vasculature. Modulation of TCTP may offer a therapeutic target for hypertension and in vascular contractility dysfunction.

Interaction of translationally controlled tumor protein with Apaf-1 is involved in the development of chemoresistance in HeLa cells

Background

Translationally controlled tumor protein (TCTP), alternatively called fortilin, is believed to be involved in the development of the chemoresistance of tumor cells against anticancer drugs such as etoposide, taxol, and oxaliplatin, the underlying mechanisms of which still remain elusive.

Methods

Cell death analysis of TCTP-overexpressing HeLa cells was performed following etoposide treatment to assess the mitochondria-dependent apoptosis. Apoptotic pathway was analyzed through measuring the cleavage of epidermal growth factor receptor (EGFR) and phospholipase C-γ (PLC-γ), caspase activation, mitochondrial membrane perturbation, and cytochrome c release by flow cytometry and western blotting. To clarify the role of TCTP in the inhibition of apoptosome, in vitro apoptosome reconstitution and immunoprecipitation was used. Pull-down assay and silver staining using the variants of Apaf-1 protein was applied to identify the domain that is responsible for its interaction with TCTP.

Results

In the present study, we confirmed that adenoviral overexpression of TCTP protects HeLa cells from cell death induced by cytotoxic drugs such as taxol and etoposide. TCTP antagonized the mitochondria-dependent apoptotic pathway following etoposide treatment, including mitochondrial membrane damage and resultant cytochrome c release, activation of caspase-9, and -3, and eventually, the cleavage of EGFR and PLC-γ. More importantly, TCTP interacts with the caspase recruitment domain (CARD) of Apaf-1 and is incorporated into the heptameric Apaf-1 complex, and that C-terminal cleaved TCTP specifically associates with Apaf-1 of apoptosome in apoptosome-forming condition thereby inhibiting the amplification of caspase cascade.

Conclusions

TCTP protects the cancer cells from etoposide-induced cell death by inhibiting the mitochondria-mediated apoptotic pathway. Interaction of TCTP with Apaf-1 in apoptosome is involved in the molecular mechanism of TCTP-induced chemoresistance. These findings suggest that TCTP may serve as a therapeutic target for chemoresistance in cancer treatment.

TCTP as therapeutic target in cancers

The translationally controlled tumor protein (TCTP) is a highly conserved protein present in eukaryotic organisms. This protein, located both in the cytoplasmic and the nucleus, is expressed in various tissues and is regulated in response to a wide range of extracellular stimuli. TCTP interacts with itself and other protein including MCL1 and p53. TCTP has been shown to play an important role in physiological events, such as cell proliferation, cell death and immune responses but also in stress response and tumor reversion. Moreover, TCTP expression is associated with malignancy and chemoresistance. In this review, we will evaluate pathways regulated by TCTP and current inhibitory strategy to target TCTP in cancerous diseases.

TCTP promotes glioma cell proliferation in vitro and in vivo via enhanced β-catenin/TCF-4 transcription

Background The translationally controlled tumor protein (TCTP) is a multifunctional protein that plays important roles in immune responses, cell proliferation, tumorigenicity and cell apoptosis. Here, we examined the clinical value of TCTP in glioma patient survival and investigated the functional roles and mechanism of TCTP in glioma development. Methods TCTP expression was determined through immunohistochemical staining, immunoblotting, and quantitative real-time PCR (qRT-PCR). TCTP or TCF-4 expression was silenced using short hairpin (sh) RNA. In vitro cell proliferation was detected using MTT, BrdU and colony formation assays, and in vivo tumor growth was performed using the xenograft model. TCTP/TCF-4/β-catenin association was detected using a co-immunoprecipitation (co-IP) assay. TCF-4 transcription activity was detected using a TOPflash/FOPflash report gene assay. Wnt/β-catenin-targeted gene expression was detected through Western blotting. Results TCTP protein levels were significantly elevated in high-grade gliomas compared with low-grade gliomas and normal brain tissues. Importantly, the expression of TCTP was significantly associated with poorer overall survival and disease-free survival, and TCTP also reduced the survival rate after treatment with radiotherapy and temozolomide (RT-TMZ) for glioma patients. The ectopic expression of TCTP enhanced glioma cell proliferation both in vitro and in vivo, whereas the knockdown of TCTP inhibited this effect. Similarly, the overexpression of TCTP increased β-catenin binding to TCF-4, TOPflash report gene transcription activity, and the expression of Wnt/β-catenin signaling target genes including c-Myc and cyclin D1; notably, the knockdown of TCTP reduced these effects. The knockdown of TCF-4 using shRNA rescued the enhanced cell proliferation induced by the overexpression of TCTP. Conclusion TCTP is associated with reduced survival of glioma patients and induces glioma tumor growth through enhanced Wnt/β-catenin signaling.

The C-terminal cysteine of turbot Scophthalmus maximus translationally controlled tumour protein plays a key role in antioxidation and growth-promoting functions

The translationally controlled tumour protein (TCTP) of turbot Scophthalmus maximus (SmTCTP) contains only one cysteine (Cys¹⁷⁰) at the C-terminal end. The biological role of this C-terminal Cys¹⁷⁰ in the antioxidation and growth-promoting functions of SmTCTP was examined by site-directed mutation of C170A (Cys¹⁷⁰ →Ala¹⁷⁰). It was found that C170A mutation not only obviously decreased the antioxidation capacity of the mutant-smtctp-transformed bacteria exposed to 0·22 mM hydrogen peroxide, but also significantly interrupted the normal growth and survival of the mutant-smtctp-transformed bacteria and flounder Paralichthys olivaceus gill (FG) cells, indicating a key role played by Cys¹⁷⁰ in the antioxidation and growth-promoting functions of SmTCTP. This study also suggested that the self-dimerization or dimerization with other interacting proteins is critical to the growth-promoting function of SmTCTP.

The role of CcTpt1 in scale and early embryo development in common carp (Cyprinus carpio, Cyprinidae)

The full length cDNA sequence of the Tpt1/TCTP (Tumor protein, Translationally-controlled1) gene was identified from Common Carp (Cyprinus carpio, Cyprinidae), and was designated as CcTpt1 gene. The CDS is 510 bp and encodes a 170-amino acid peptide with a typical Tpt1 signature 2 domain, and is a typical Tpt1 protein. The deduced amino acid sequence of Tpt1 shared significant identity with the Tpt1 from other animals. A phylogenetic tree analysis revealed that the Common Carp Tpt1 protein has the closest genetic relationship and evolutional distance with Tpt1 from Medaka (Oryzias Latipes). Analysis by RT-PCR showed that the Tpt1 mRNA was detected in heart, liver, gill, kidney, muscle and skin. In embryogenesis, the Tpt1 mRNA was expressed gradually stronger from two-cell stage until prim-5 stage by whole-mount in situ. In larval stage, the Tpt1 was specifically expressed at eyes and brain, later at the ear stone, intestines, gills and internal organs. In addition, the Tpt1 was also found to be expressed in skin matrix being developed into scales and gradually disappeared when the scales were fully formed. These data suggested that the CcTpt1 may play important roles in early embryogenesis and scale initiation in fish.

Translationally controlled tumor protein, a dual functional protein involved in the immune response of the silkworm, Bombyx mori

Insect gut immunity is the first line of defense against oral infection. Although a few immune-related molecules in insect intestine has been identified by genomics or proteomics approach with comparison to well-studied tissues, such as hemolymph or fat body, our knowledge about the molecular mechanism underlying the gut immunity which would involve a variety of unidentified molecules is still limited. To uncover additional molecules that might take part in pathogen recognition, signal transduction or immune regulation in insect intestine, a T7 phage display cDNA library of the silkworm midgut is constructed. By use of different ligands for biopanning, Translationally Controlled Tumor Protein (TCTP) has been selected. BmTCTP is produced in intestinal epithelial cells and released into the gut lumen. The protein level of BmTCTP increases at the early time points during oral microbial infection and declines afterwards. In vitro binding assay confirms its activity as a multi-ligand binding molecule and it can further function as an opsonin that promotes the phagocytosis of microorganisms. Moreover, it can induce the production of anti-microbial peptide via a signaling pathway in which ERK is required and a dynamic tyrosine phosphorylation of certain cytoplasmic membrane protein. Taken together, our results characterize BmTCTP as a dual-functional protein involved in both the cellular and the humoral immune response of the silkworm, Bombyx mori.

A new antiallergic agent that binds to dimerized translationally controlled tumor protein and inhibits allergic symptoms is nontoxic

Dimerized translationally controlled tumor protein (dTCTP) plays a role in allergic diseases. A 7-mer peptide, dimerized translationally binding protein 2 (dTBP2), binds to dTCTP and inhibits dTCTP, suggesting that the 7-mer peptide may have therapeutic potential. We assessed the safety of dTBP2 by examining its cytotoxicity to both human bronchial epithelial cells and mice. dTBP2 did not cause cytotoxicity to the epithelial cells in concentrations up to 100 μg/ml. Also, dTBP2 caused no adverse effects upon repeated administration of 50 mg/kg over 24 h to mice. Hence, we conclude that dTBP2 is a safe candidate drug for use in the therapy of allergic diseases.

Ursodeoxycholic acid attenuates colonic epithelial secretory function

Dihydroxy bile acids, such as chenodeoxycholic acid (CDCA), are well known to promote colonic fluid and electrolyte secretion, thereby causing diarrhoea associated with bile acid malabsorption. However, CDCA is rapidly metabolised by colonic bacteria to ursodeoxycholic acid (UDCA), the effects of which on epithelial transport are poorly characterised. Here, we investigated the role of UDCA in the regulation of colonic epithelial secretion. Cl(-) secretion was measured across voltage-clamped monolayers of T84 cells and muscle-stripped sections of mouse or human colon. Cell surface biotinylation was used to assess abundance/surface expression of transport proteins. Acute (15 min) treatment of T84 cells with bilateral UDCA attenuated Cl(-) secretory responses to the Ca(2+) and cAMP-dependent secretagogues carbachol (CCh) and forskolin (FSK) to 14.0 ± 3.8 and 40.2 ± 7.4% of controls, respectively (n = 18, P < 0.001). Investigation of the molecular targets involved revealed that UDCA acts by inhibiting Na(+)/K(+)-ATPase activity and basolateral K(+) channel currents, without altering their cell surface expression. In contrast, intraperitoneal administration of UDCA (25 mg kg(-1)) to mice enhanced agonist-induced colonic secretory responses, an effect we hypothesised to be due to bacterial metabolism of UDCA to lithocholic acid (LCA). Accordingly, LCA (50-200 μm) enhanced agonist-induced secretory responses in vitro and a metabolically stable UDCA analogue, 6α-methyl-UDCA, exerted anti-secretory actions in vitro and in vivo. In conclusion, UDCA exerts direct anti-secretory actions on colonic epithelial cells and metabolically stable derivatives of the bile acid may offer a new approach for treating intestinal diseases associated with diarrhoea.

Molecular cloning, expression profiles and characterization of a novel translationally controlled tumor protein in rubber tree (Hevea brasiliensis)

The translationally controlled tumor protein (TCTP) is a multi-functioning protein that carries out vital roles in various life processes. In this study, a new TCTP gene, designated as HbTCTP1, was isolated in Hevea brasiliensis. The full-length complementary DNA (cDNA) of HbTCTP1 contained a maximum open reading frame (ORF) of 507base pair (bp) encoding 168 amino acids. The sequence comparison showed that the deduced HbTCTP1 indicated high identities to plant TCTP proteins, and clustered in the dicot cluster of plant TCTPs. Although HbTCTP1 and human TCTP proteins did not parallel in overall sequence similarity, they indicated highly similar 3D structures with a nearly identical spatial organization of α-helices, β-sheets, and coil regions. Real time reverse-transcription PCR (RT-PCR) analyses showed that HbTCTP1 was expressed throughout different tissues and developmental stages of leaves. Besides being related to tapping panel dryness (TPD), the HbTCTP1 transcripts were regulated by various treatments, including drought, low temperature, high salt, ethrel (ET), wounding, H2O2, and methyl jasmonate (Me-JA) treatments. The recombinant HbTCTP1 fusion protein was shown to protect supercoiled plasmid DNA from damages induced by metal-catalyzed generation of reactive oxygen species. The (45)Ca(2+)-overlay assay showed that HbTCTP1 was a calcium-binding protein. Our results are greatly helpful in understanding the molecular characterization and expression profiles of HbTCTP1, and lay the foundation for further analyzing the function of HbTCTP1 in rubber tree.

Na(+),K (+)-ATPase as a docking station: protein-protein complexes of the Na(+),K (+)-ATPase

The Na(+),K(+)-ATPase, or sodium pump, is well known for its role in ion transport across the plasma membrane of animal cells. It carries out the transport of Na(+) ions out of the cell and of K(+) ions into the cell and thus maintains electrolyte and fluid balance. In addition to the fundamental ion-pumping function of the Na(+),K(+)-ATPase, recent work has suggested additional roles for Na(+),K(+)-ATPase in signal transduction and biomembrane structure. Several signaling pathways have been found to involve Na(+),K(+)-ATPase, which serves as a docking station for a fast-growing number of protein interaction partners. In this review, we focus on Na(+),K(+)-ATPase as a signal transducer, but also briefly discuss other Na(+),K(+)-ATPase protein-protein interactions, providing a comprehensive overview of the diverse signaling functions ascribed to this well-known enzyme.

Binding of Translationally Controlled Tumour Protein to the N-terminal domain of HDM2 is inhibited by nutlin-3

Translationally Controlled Tumour Protein (TCTP), a highly conserved protein present in all eukaryotic organisms, has a number of intracellular and extracellular functions including an anti-apoptotic role. TCTP was recently shown to interact with both p53 and HDM2, inhibiting auto-ubiquitination of the latter and thereby promoting p53 degradation. In this study, we further investigated the interaction between TCTP and HDM2, mapping the reciprocal binding sites of TCTP and HDM2. TCTP primarily interacts with the N-terminal, p53-binding region of HDM2 through its highly basic domain 2. Furthermore, we discovered that Nutlin-3, a small molecule known to promote apoptosis and cell cycle arrest by blocking binding between HDM2 and p53, has a similar inhibitory effect on the interaction of HDM2 and TCTP. This result may provide an additional explanation of how Nutlin-derived compounds currently in clinical trials function to promote apoptosis in cancer cells.

Biological effects of Mammalian translationally controlled tumor protein (TCTP) on cell death, proliferation, and tumorigenesis

Translationally controlled tumor protein (TCTP) is a highly conserved protein found in eukaryotes, across animal and plant kingdoms and even in yeast. Mammalian TCTP is ubiquitously expressed in various tissues and cell types. TCTP is a multifunctional protein which plays important roles in a number of cell physiological events, such as immune responses, cell proliferation, tumorigenicity, and cell death, including apoptosis. Recent identification of TCTP as an antiapoptotic protein has attracted interest of many researchers in the field. The mechanism of antiapoptotic activity, however, has not been solved completely, and TCTP might inhibit other types of cell death. Cell death (including apoptosis) is closely linked to proliferation and tumorigenesis. In this context, we review recent findings regarding the role of TCTP in cell death, proliferation, and tumorigenesis and discuss the mechanisms.

Hypertension resulting from overexpression of translationally controlled tumor protein increases the severity of atherosclerosis in apolipoprotein E knock-out mice

Hypertension is a well-established etiological factor for atherogenesis. We previously showed that transgenic mice overexpressing translationally controlled tumor protein (TCTP) develop systemic arterial hypertension. In this study we explored the cardiovascular effects of TCTP overexpression and possibly of the resultant hypertension on the severity of atherosclerosis in apolipoprotein E-deficient mice. Through multiple mating of TCTP-overexpressing transgenic mice (TCTP-TG) with apolipoprotein E knock-out mice (ApoE KO), we generated non-transgenic (nTG), TCTP-TG, nTG/ApoE KO and TCTP-TG/ApoE KO mice with similar genetic background. Male mice, 7-week old, were fed a lipid-enriched Western diet for 16 weeks, and blood pressure and body weight change were monitored every 2 weeks. Plasma lipid profiles and atherosclerotic lesions in aorta were quantified at the end of study. We found that blood pressure levels of TCTP-TG and TCTP-TG/ApoE KO, were similarly elevated while nTG and nTG/ApoE KO mice were normotensive. TCTP overexpression in ApoE KO mice led to significant exacerbation of atherosclerotic lesions. Feeding Western diet resulted in increases in total cholesterol, triglyceride (TG) and low density lipoprotein, and decreased high density lipoprotein (HDL) in ApoE KO mice. No significant differences were found in plasma lipid profiles of nTG/ApoE KO and TCTP-TG/ApoE KO. This study suggests that overexpression of TCTP, which induces hypertension, also accelerates the development of atherosclerotic lesion caused by high-fat and high-cholesterol diet without significantly altering plasma lipid profiles. We conclude that TCTP-induced hypertension could increase the severity of atherosclerotic lesion and suggest that inhibition of TCTP or its signaling pathways may be a potential approach to the therapy of both diseases, hypertension and atherosclerosis.

Characterization of a novel binding protein for Fortilin/TCTP--component of a defense mechanism against viral infection in Penaeus monodon

The Fortilin (also known as TCTP) in Penaeus monodon (PmFortilin) and Fortilin Binding Protein 1 (FBP1) have recently been shown to interact and to offer protection against the widespread White Spot Syndrome Virus infection. However, the mechanism is yet unknown. We investigated this interaction in detail by a number of in silico and in vitro analyses, including prediction of a binding site between PmFortilin/FBP1 and docking simulations. The basis of the modeling analyses was well-conserved PmFortilin orthologs, containing a Ca²⁺-binding domain at residues 76–110 representing a section of the helical domain, the translationally controlled tumor protein signature 1 and 2 (TCTP_1, TCTP_2) at residues 45–55 and 123–145, respectively. We found the pairs Cys59 and Cys76 formed a disulfide bond in the C-terminus of FBP1, which is a common structural feature in many exported proteins and the “x–G–K–K” pattern of the amidation site at the end of the C-terminus. This coincided with our previous work, where we found the “x–P–P–x” patterns of an antiviral peptide also to be located in the C-terminus of FBP1. The combined bioinformatics and in vitro results indicate that FBP1 is a transmembrane protein and FBP1 interact with N-terminal region of PmFortilin.

Upregulation of TCTP expression in human skin squamous cell carcinoma increases tumor cell viability through anti-apoptotic action of the protein

The translationally controlled tumor protein (TCTP) is an anti-apoptotic protein, which is highly expressed in several human cancer types. However, the role of TCTP in skin cancers, including squamous cell carcinoma (SCC), has not been investigated. In this study, we analyzed the expression of TCTP in cutaneous SCC samples using immunohistochemistry in two epidermoid SCC cell lines, A431 and SCL-1, using western blot analysis. We further investigated the role of TCTP in skin cancinogenesis by silencing the TPT1 gene using small interfering RNA (siRNA) in the SCC cell line A431. Our results demonstrated that TCTP was overexpressed in cutaneous SCC cells, compared to normal skin keratinocytes. In addition, the expression of TCTP in skin SCC significantly increased with the grade of malignancy. Western blot analysis further confirmed that the expression of TCTP in the cell lines, A431 and SCL-1, was significantly higher compared to that in the normal keratinocyte cell line, HaCaT. The expression of TCTP in A431 cells was significantly downregulated by transfection with our specifically designed TCTP siRNA. We found that downregulation of TCTP expression was associated with decreased cell proliferation and increased apoptosis in A431 cells. These results suggest that the TPT1 gene may be a potential therapeutic target in skin SCC through a siRNA approach.

How NaCl raises blood pressure: a new paradigm for the pathogenesis of salt-dependent hypertension

Excess dietary salt is a major cause of hypertension. Nevertheless, the specific mechanisms by which salt increases arterial constriction and peripheral vascular resistance, and thereby raises blood pressure (BP), are poorly understood. Here we summarize recent evidence that defines specific molecular links between Na(+) and the elevated vascular resistance that directly produces high BP. In this new paradigm, high dietary salt raises cerebrospinal fluid [Na(+)]. This leads, via the Na(+)-sensing circumventricular organs of the brain, to increased sympathetic nerve activity (SNA), a major trigger of vasoconstriction. Plasma levels of endogenous ouabain (EO), the Na(+) pump ligand, also become elevated. Remarkably, high cerebrospinal fluid [Na(+)]-evoked, locally secreted (hypothalamic) EO participates in a pathway that mediates the sustained increase in SNA. This hypothalamic signaling chain includes aldosterone, epithelial Na(+) channels, EO, ouabain-sensitive α(2) Na(+) pumps, and angiotensin II (ANG II). The EO increases (e.g.) hypothalamic ANG-II type-1 receptor and NADPH oxidase and decreases neuronal nitric oxide synthase protein expression. The aldosterone-epithelial Na(+) channel-EO-α(2) Na(+) pump-ANG-II pathway modulates the activity of brain cardiovascular control centers that regulate the BP set point and induce sustained changes in SNA. In the periphery, the EO secreted by the adrenal cortex directly enhances vasoconstriction via an EO-α(2) Na(+) pump-Na(+)/Ca(2+) exchanger-Ca(2+) signaling pathway. Circulating EO also activates an EO-α(2) Na(+) pump-Src kinase signaling cascade. This increases the expression of the Na(+)/Ca(2+) exchanger-transient receptor potential cation channel Ca(2+) signaling pathway in arterial smooth muscle but decreases the expression of endothelial vasodilator mechanisms. Additionally, EO is a growth factor and may directly participate in the arterial structural remodeling and lumen narrowing that is frequently observed in established hypertension. These several central and peripheral mechanisms are coordinated, in part by EO, to effect and maintain the salt-induced elevation of BP.

Brown spider (Loxosceles genus) venom toxins: tools for biological purposes

Venomous animals use their venoms as tools for defense or predation. These venoms are complex mixtures, mainly enriched of proteic toxins or peptides with several, and different, biological activities. In general, spider venom is rich in biologically active molecules that are useful in experimental protocols for pharmacology, biochemistry, cell biology and immunology, as well as putative tools for biotechnology and industries. Spider venoms have recently garnered much attention from several research groups worldwide. Brown spider (Loxosceles genus) venom is enriched in low molecular mass proteins (5–40 kDa). Although their venom is produced in minute volumes (a few microliters), and contain only tens of micrograms of protein, the use of techniques based on molecular biology and proteomic analysis has afforded rational projects in the area and permitted the discovery and identification of a great number of novel toxins. The brown spider phospholipase-D family is undoubtedly the most investigated and characterized, although other important toxins, such as low molecular mass insecticidal peptides, metalloproteases and hyaluronidases have also been identified and featured in literature. The molecular pathways of the action of these toxins have been reported and brought new insights in the field of biotechnology. Herein, we shall see how recent reports describing discoveries in the area of brown spider venom have expanded biotechnological uses of molecules identified in these venoms, with special emphasis on the construction of a cDNA library for venom glands, transcriptome analysis, proteomic projects, recombinant expression of different proteic toxins, and finally structural descriptions based on crystallography of toxins.