The mRNA of the translationally controlled tumor protein P23/TCTP is a highly structured RNA, which activates the dsRNA-dependent protein kinase PKR

Targeting inhibition of TCTP could inhibit proliferation and induce apoptosis in AML cells

Translationally controlled tumor protein (TCTP) is a highly conserved multifunctional protein, which participates in many important physiological processes. Recently, the roles of TCTP in cell proliferation and apoptosis, especially its close relationship with various tumors, have attracted widespread attention. In this study, we found that the protein level of TCTP was significantly reduced in acute promyelocytic leukemia cell line NB4 transfected with retinoic acid-induced gene G (RIG-G). The RIG-G was found in our previous work as a key mediator of anti-proliferative activity in retinoid/interferon-related pathways. Here, we tried to further explore the function of TCTP in the development of acute myeloid leukemia (AML) from different levels. Our results showed that inhibiting TCTP expression could attenuate AML cells proliferation and induce apoptosis both in AML cell lines and in xenograft of NOD-SCID mice. In addition, either compared with patients in complete remission or non-leukemia patients, we detected that the expression of TCTP was generally high in the fresh bone marrow of AML patients, suggesting that there was a certain correlation between TCTP and AML disease progression. Taken together, our study revealed the role of TCTP in AML development, and provided a potential target for AML treatment.

Prognostic value of translationally controlled tumor protein in colon cancer

The translationally controlled tumor protein (TCTP) is a highly conserved protein involved in a variety of normal cell functions and disease processes. Preclinical studies revealed that TCTP has anti-apoptotic properties, promotes cell growth and division and is involved in cancer progression by promoting invasion and metastasis. The present study explored the potential value of TCTP as a prognostic marker in colon cancer. A retrospective analysis of 74 patients with colon cancer was performed. Using immunohistochemistry, TCTP levels in the primary tumor were assessed semi-quantitatively by the calculation of cytoplasmic and nuclear H-score. Cytoplasmic TCTP levels in the primary tumor had no statistically significant association with disease-free survival (DFS), progression-free survival (PFS) and overall survival (OS) in the present patient population. Patients whose primary tumors had a negative nuclear TCTP expression had significantly improved clinical outcomes. The PFS for the negative nuclear TCTP expression group was 7.7 months [95% confidence interval (CI), 5.8-9.5] compared with 5.5 months (95% CI, 3.2-7.8) in the group with positive nuclear expression (P=0.023, Mantel-Cox log-rank). Patients with a negative nuclear expression of TCTP had a significantly higher median OS (22.2 months; 95% CI, 16.1-28.3) compared with those with positive TCTP nuclear expression (median 13.2 months; 95% CI, 10.1-16.3; P=0.008, Mantel-Cox log-rank). In a multivariate Cox regression model, a positive nuclear TCTP H-score was an independent risk factor for worse PFS and OS. The 1-year OS rate in the group with negative nuclear TCTP expression was 86.3% compared with 56.5% in patients with positive nuclear TCTP expression (P=0.008). The present study suggested that semiquantitative H-score measurement of TCTP levels in the nuclei of tumor cells from the primary tumor is a potential prognostic marker for clinical outcomes in patients with colon cancer.

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.

The mRNA of TCTP functions as a sponge to maintain homeostasis of TCTP protein levels in hepatocellular carcinoma

Translationally controlled tumor protein (TCTP) is a highly conserved protein that accumulated in the tumorigenesis of various malignancies. Despite the important role of TCTP protein in tumor progression, the precise function and underlying mechanistic regulation of TCTP mRNA in hepatocellular carcinoma (HCC) remain unclear. In this study, we found that TCTP protein was overexpressed in HCC patients but TCTP mRNA expression levels were reversed. TCTP knockout HCC cells exhibited attenuated abilities of proliferation, migration, and invasion. The knockdown of TCTP by siRNA effectively reduced TCTP mRNA levels but not protein levels in HCC cells. Moreover, although the constitutive knockdown of TCTP inhibited almost 80% of TCTP protein expression levels in tumors of wildtype transgenic mice (TCTP KD/WT), partial restoration of TCTP protein expression was observed in the tumors of heterozygous TCTP mice (TCTP KD/TCTP±). The blockage of mRNA synthesis with ActD stimulated TCTP protein expression in HCC cells. In contrast, combined treatment with ActD and CHX or MG132 treatment alone did not lead to the TCTP protein accumulation in cells. Furthermore, following the introduction of exogenous TCTP in cells and orthotopic HCC tumor models, the endogenous TCTP protein did not change with the recombinational TCTP expression and kept a rather stable level. Dual-luciferase assays revealed that the coding sequence of TCTP mRNA functions as a sponge to regulate the TCTP protein expression. Collectively, our results indicated that the TCTP mRNA and protein formed a closed regulatory circuit and works as a buffering system to keep the homeostasis of TCTP protein levels in HCC.

Dysregulation of TCTP in Biological Processes and Diseases

Translationally controlled tumor protein (TCTP), also called histamine releasing factor (HRF) or fortilin, is a multifunctional protein present in almost all eukaryotic organisms. TCTP is involved in a range of basic cell biological processes, such as promotion of growth and development, or cellular defense in response to biological stresses. Cellular TCTP levels are highly regulated in response to a variety of physiological signals, and regulatory mechanism at various levels have been elucidated. Given the importance of TCTP in maintaining cellular homeostasis, it is not surprising that dysregulation of this protein is associated with a range of disease processes. Here, we review recent progress that has been made in the characterisation of the basic biological functions of TCTP, in the description of mechanisms involved in regulating its cellular levels and in the understanding of dysregulation of TCTP, as it occurs in disease processes such as cancer.

Role and Fate of TCTP in Protein Degradative Pathways

This chapter focuses on published studies specifically concerning TCTP and its involvement in degradation or stabilization of various proteins, and also in its own degradation in different ways. The first part relates to the inhibition of proteasomal degradation of proteins. This can be achieved by masking ubiquitination sites of specific partners, by favoring ubiquitin E3 ligase degradation, or by regulating proteasome activity. The second part addresses the ability of TCTP to favor degradation of specific proteins through proteasome or macroautophagic pathways. The third part discusses about the different ways by which TCTP has been shown to be degraded.

Growth Cone Tctp Is Dynamically Regulated by Guidance Cues

Translationally controlled tumor protein (Tctp) contributes to retinal circuitry formation by promoting axon growth and guidance, but it remains unknown to what extent axonal Tctp specifically influences axon development programs. Various genome-wide profiling studies have ranked tctp transcripts among the most enriched in the axonal compartment of distinct neuronal populations, including embryonic retinal ganglion cells (RGCs), suggesting its expression can be regulated locally and that this may be important during development. Here, we report that growth cone Tctp levels change rapidly in response to Netrin-1 and Ephrin-A1, two guidance cues encountered by navigating RGC growth cones. This regulation is opposite in effect, as we observed protein synthesis- and mTORC1-dependent increases in growth cone Tctp levels after acute treatment with Netrin-1, but a decline upon exposure to Ephrin-A1, an inhibitor of mTORC1. Live imaging with translation reporters further showed that Netrin-1-induced synthesis of Tctp in growth cones is driven by a short 3'untranslated region (3'UTR) tctp mRNA isoform. However, acute inhibition of de novo Tctp synthesis in axons did not perturb the advance of retinal projections through the optic tract in vivo, indicating that locally produced Tctp is not necessary for normal axon growth and guidance.

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.

Allele-specific SHAPE-MaP assessment of the effects of somatic variation and protein binding on mRNA structure

The impact of inherited and somatic mutations on messenger RNA (mRNA) structure remains poorly understood. Recent technological advances that leverage next-generation sequencing to obtain experimental structure data, such as SHAPE-MaP, can reveal structural effects of mutations, especially when these data are incorporated into structure modeling. Here, we analyze the ability of SHAPE-MaP to detect the relatively subtle structural changes caused by single-nucleotide mutations. We find that allele-specific sorting greatly improved our detection ability. Thus, we used SHAPE-MaP with a novel combination of clone-free robotic mutagenesis and allele-specific sorting to perform a rapid, comprehensive survey of noncoding somatic and inherited riboSNitches in two cancer-associated mRNAs, TPT1 and LCP1 Using rigorous thermodynamic modeling of the Boltzmann suboptimal ensemble, we identified a subset of mutations that change TPT1 and LCP1 RNA structure, with approximately 14% of all variants identified as riboSNitches. To confirm that these in vitro structures were biologically relevant, we tested how dependent TPT1 and LCP1 mRNA structures were on their environments. We performed SHAPE-MaP on TPT1 and LCP1 mRNAs in the presence or absence of cellular proteins and found that both mRNAs have similar overall folds in all conditions. RiboSNitches identified within these mRNAs in vitro likely exist under biological conditions. Overall, these data reveal a robust mRNA structural landscape where differences in environmental conditions and most sequence variants do not significantly alter RNA structural ensembles. Finally, predicting riboSNitches in mRNAs from sequence alone remains particularly challenging; these data will provide the community with benchmarks for further algorithmic development.

Characterization of Translationally Controlled Tumour Protein from the Sea Anemone Anemonia viridis and Transcriptome Wide Identification of Cnidarian Homologues

Gene family encoding translationally controlled tumour protein (TCTP) is defined as highly conserved among organisms; however, there is limited knowledge of non-bilateria. In this study, the first TCTP homologue from anthozoan was characterised in the Mediterranean Sea anemone, Anemonia viridis. The release of the genome sequence of Acropora digitifera, Exaiptasia pallida, Nematostella vectensis and Hydra vulgaris enabled a comprehensive study of the molecular evolution of TCTP family among cnidarians. A comparison among TCTP members from Cnidaria and Bilateria showed conserved intron exon organization, evolutionary conserved TCTP signatures and 3D protein structure. The pattern of mRNA expression profile was also defined in A. viridis. These analyses revealed a constitutive mRNA expression especially in tissues with active proliferation. Additionally, the transcriptional profile of A. viridis TCTP (AvTCTP) after challenges with different abiotic/biotic stresses showed induction by extreme temperatures, heavy metals exposure and immune stimulation. These results suggest the involvement of AvTCTP in the sea anemone defensome taking part in environmental stress and immune responses.

Insights into the role and regulation of TCTP in skeletal muscle

The translationally controlled tumor protein (TCTP) is upregulated in a range of cancer cell types, in part, by the activation of the mechanistic target of rapamycin (mTOR). Recently, TCTP has also been proposed to act as an indirect activator of mTOR. While it is known that mTOR plays a major role in the regulation of skeletal muscle mass, very little is known about the role and regulation of TCTP in this post-mitotic tissue. This study shows that muscle TCTP and mTOR signaling are upregulated in a range of mouse models (mdx mouse, mechanical load-induced hypertrophy, and denervation- and immobilization-induced atrophy). Furthermore, the increase in TCTP observed in the hypertrophic and atrophic conditions occurred, in part, via a rapamycin-sensitive mTOR-dependent mechanism. However, the overexpression of TCTP was not sufficient to activate mTOR signaling (or increase protein synthesis) and is thus unlikely to take part in a recently proposed positive feedback loop with mTOR. Nonetheless, TCTP overexpression was sufficient to induce muscle fiber hypertrophy. Finally, TCTP overexpression inhibited the promoter activity of the muscle-specific ubiquitin proteasome E3-ligase, MuRF1, suggesting that TCTP may play a role in inhibiting protein degradation. These findings provide novel data on the role and regulation of TCTP in skeletal muscle in vivo.

Knockdown of translationally controlled tumor protein inhibits growth, migration and invasion of lung cancer cells

AIM

To investigate the role of translationally controlled tumor protein (TCTP) in lung cancer development.

MAIN METHODS

A549 and HCC827 cells were transfected with shRNA specifically targeting TCTP mRNA. Cell growth was assessed by colony formation assay and cell counting kit-8. Cell cycle and apoptosis were analyzed by flow cytometry. Cell migration and invasion was measured by scratch and transwell assays. In vivo tumorigenicity was evaluated by tumor xenografts in nude mice.

KEY FINDINGS

TCTP-silenced cells displayed a reduced ability of colony formation and a lower rate of proliferation in vitro. Knockdown of TCTP arrested cell cycle at G1 phase and led to downregulated expression of cyclins B1, D1 and E. Moreover, silencing of TCTP induced apoptosis and altered the levels of apoptosis-regulatory proteins such as cleaved caspase-3, Bcl-2, Bax and p53. Silencing of TCTP also inhibited migration and invasion of lung cancer cells. In addition, TCTP-silenced A549 cells, when subcutaneously inoculated in nude mice, formed tumors at a significantly slower rate.

SIGNIFICANCE

Our in vitro and in vivo data indicate that silencing of TCTP inhibits growth, migration and invasion of lung cancer cells. Thus, TCTP may be a potential target for lung cancer therapy.

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.

Translationally controlled tumour protein TCTP is induced early in human colorectal tumours and contributes to the resistance of HCT116 colon cancer cells to 5-FU and oxaliplatin

Background

Translationally controlled tumour protein TCTP is an anti-apoptotic protein frequently overexpressed in cancers, where high levels are often associated with poor patient outcome. TCTP may be involved in protecting cancer cells against the cytotoxic action of anti-cancer drugs. Here we study the early increase of TCTP levels in human colorectal cancer (CRC) and the regulation of TCTP expression in HCT116 colon cancer cells, in response to treatment with the anti-cancer drugs 5-FU and oxaliplatin.

Methods

Using immunohistochemistry, we assessed TCTP levels in surgical samples from adenomas and adenocarcinomas of the colon, compared to normal colon tissue. We also studied the regulation of TCTP in HCT116 colon cancer cells in response to 5-FU and oxaliplatin by western blotting. TCTP mRNA levels were assessed by RT-qPCR. We used mTOR kinase inhibitors to demonstrate mTOR-dependent translational regulation of TCTP under these conditions. Employing the Real-Time Cell Analysis (RTCA) System and the MTS assay, we investigated the effect of TCTP-knockdown on the sensitivity of HCT116 cells to the anti-cancer drugs 5-FU and oxaliplatin.

Results

1. TCTP levels are significantly increased in colon adenomas and adenocarcinomas, compared to normal colon tissue. 2. TCTP protein levels are about 4-fold upregulated in HCT116 colon cancer cells, in response to 5-FU and oxaliplatin treatment, whereas TCTP mRNA levels are down regulated. 3. mTOR kinase inhibitors prevented the up-regulation of TCTP protein, indicating that TCTP is translationally regulated through the mTOR complex 1 signalling pathway under these conditions. 4. Using two cellular assay systems, we demonstrated that TCTP-knockdown sensitises HCT116 cells to the cytotoxicity caused by 5-FU and oxaliplatin.

Conclusions

Our results demonstrate that TCTP levels increase significantly in the early stages of CRC development. In colon cancer cells, expression of this protein is largely upregulated during treatment with the DNA-damaging anti-cancer drugs 5-FU and oxaliplatin, as part of the cellular stress response. TCTP may thus contribute to the development of anti-cancer drug resistance. These findings indicate that TCTP might be suitable as a biomarker and that combinatorial treatment using 5-FU/oxaliplatin, together with mTOR kinase inhibitors, could be a route to preventing the development of resistance to these drugs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-017-0164-3) contains supplementary material, which is available to authorized users.

Acetylation of translationally controlled tumor protein promotes its degradation through chaperone-mediated autophagy

Translationally controlled tumor protein (Tpt1/TCTP) is a multi-functional cytosolic protein whose cellular levels are finely tuned. TCTP regulates protein behavior by favoring stabilization of protein partners or on the contrary by promoting degradation of others. TCTP has been shown to be transcriptionally and translationally regulated, but much less is known about its degradation process. In this study, we present evidence that chaperone-mediated autophagy (CMA) contributes to TCTP regulation. CMA allows lysosomal degradation of specific cytosolic proteins on a molecule-by-molecule basis. It contributes to cellular homeostasis especially by acting as a quality control for cytosolic proteins in response to stress and as a way of regulating the level of specific proteins. Using a variety of approaches, we show that CMA degradation of TCTP is Hsc70 and LAMP-2A dependent. Our data indicate that (i) TCTP directly interacts with Hsc70; (ii) silencing LAMP-2A in MEFs using siRNA leads to inhibition of TCTP downregulation; (iii) TCTP is relocalized from a diffuse cytosolic pattern to a punctate lysosomal pattern when CMA is upregulated; (iv) TCTP is degraded in vitro by purified lysosomes. Importantly, using lysine-mutated forms of TCTP, we show that acetylation of Lysine 19 generates a KFERQ-like motif and promotes binding to Hsc70, lysosome targeting and TCTP degradation by CMA. Altogether these results indicate that TCTP is degraded by chaperone-mediated autophagy in an acetylation dependent manner.

Roles of the Translationally Controlled Tumor Protein (TCTP) in Plant Development

The Translationally Controlled Tumor Protein (TCTP) is a conserved protein which expression was associated with several biochemical and cellular functions. Loss-of-function mutants are lethal both in animals and in plants, making the identification of its exact role difficult. Recent data using the model plant Arabidopsis thaliana provided the first viable adult knockout for TCTP and helped addressing the biological role of TCTP during organ development and the functional conservation between plants and animals. This chapter summarizes our up to date knowledge about the role of TCTP in plants and discuss about conserved functions and mechanisms between plants and animals.

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.

Structure-Function Relationship of TCTP

The translationally controlled tumor protein (TCTP) is a small, multifunctional protein found in most, if not all, eukaryotic lineages, involved in a myriad of key regulatory processes. Among these, the control of proliferation and inhibition of cell death, as well as differentiation, are the most important, and it is probable that other responses are derived from the ability of TCTP to influence them in both unicellular and multicellular organisms. In the latter, an additional function for TCTP stems from its capacity to be secreted via a nonclassical pathway and function in a non-cell autonomous (paracrine) manner, thus affecting the responses of neighboring or distant cells to developmental or environmental stimuli (as in the case of serum TCTP/histamine-releasing factor in mammals and phloem TCTP in Arabidopsis). The additional ability to traverse membranes without a requirement for transmembrane receptors adds to its functional flexibility. The long-distance transport of TCTP mRNA and protein in plants via the vascular system supports the notion that an important aspect of TCTP function is its ability to influence the response of neighboring and distant cells to endogenous and exogenous signals in a supracellular manner. The predicted tridimensional structure of TCTPs indicates a high degree of conservation, more than its amino acid sequence similarity could suggest. However, subtle differences in structure could lead to different activities, as evidenced by TCTPs secreted by Plasmodium spp. Similar structural variations in animal and plant TCTPs, likely the result of convergent evolution, could lead to deviations from the canonical function of this group of proteins, which could have an impact from a biomedical and agricultural perspectives.

Elusive Role of TCTP Protein and mRNA in Cell Cycle and Cytoskeleton Regulation

Translationally Controlled Tumor-associated Protein (TCTP) is a small, 23 kDa multifunctional and ubiquitous protein localized both in the cytoplasm and in the nucleus of eukaryotic cells. It is evolutionarily highly conserved. Certain aspects of its structure show remarkable similarities to guanine nucleotide-free chaperons Mss4 and Dss4 suggesting that at least some functions of TCTP may depend on its chaperon-like action on other proteins. Besides other functions, TCTP is clearly involved in cell cycle regulation. It is also regulated in a cell-cycle-dependent manner suggesting a reciprocal interaction between this protein and the cell cycle-regulating machinery. TCTP also interacts with the cytoskeleton, mostly with actin microfilaments (MFs) and microtubules (MTs). It regulates the cytoskeleton organization and through this action it also influences cell shape and motility. The exact role of TCTP in cell cycle and cytoskeleton regulation is certainly not fully understood. In this chapter, we summarize recent data on cell cycle and cytoskeletal aspects of TCTP regulatory role.

Serum translationally controlled tumor protein is involved in rat liver regeneration after hepatectomy

AIM

The translationally controlled tumor protein (TCTP) has been reported to promote progression of many physiological processes. However, whether TCTP is involved in liver regeneration has been rarely studied. This study aimed to investigate the potential role of serum TCTP in liver regeneration after two-thirds partial hepatectomy.

METHODS

The synthesis rate and accumulated expression of TCTP was assessed by phosphor imaging and Western blot analysis, respectively. The mRNA expression of tctp was analyzed by quantitative real-time PCR. The effect of serum TCTP on hepatocyte proliferation was investigated by bromodeoxyuridine incorporation, liver/body weight ratio, albumin concentration, and histological examination of liver following treatment of rat with anti-TCTP antibody or prokaryotic TCTP protein before hepatectomy. The MTT assay was used to examine effect of TCTP on hepatocyte proliferation in vitro.

RESULTS

The results showed that the expression of intracellular and serum TCTP protein was significantly increased in rats after two-thirds partial hepatectomy. In vivo bromodeoxyuridine labeling assay suggested that treatment with anti-TCTP antibody before hepatectomy significantly decreased hepatocyte proliferation and liver/body weight ratio. The prokaryotic TCTP had a potential promoting effect on hepatocyte proliferation both in vivo and in vitro, although prokaryotic TCTP given to rats prior to hepatectomy did not increase the proliferation ratio or liver/body weight ratio. Furthermore, anti-TCTP antibody pretreatment decreased the expression of cyclin E, cdk2, and interleukin-6 in rat liver.

CONCLUSION

These findings suggest serum TCTP is involved in rat liver regeneration through promoting hepatocyte proliferation.

Incredible RNA: Dual Functions of Coding and Noncoding

Since the RNA world hypothesis was proposed, a large number of regulatory noncoding RNAs (ncRNAs) have been identified in many species, ranging from microorganisms to mammals. During the characterization of these newly discovered RNAs, RNAs having both coding and noncoding functions were discovered, and these were considered bifunctional RNAs. The recent use of computational and high-throughput experimental approaches has revealed increasing evidence of various sources of bifunctional RNAs, such as protein-coding mRNAs with a noncoding isoform and long ncRNAs bearing a small open reading frame. Therefore, the genomic diversity of Janus-faced RNA molecules that have dual characteristics of coding and noncoding indicates that the functional roles of RNAs have to be revisited in cells on a genome-wide scale. Such studies would allow us to further understand the complex gene-regulatory network in cells. In this review, we discuss three major genomic sources of bifunctional RNAs and present a handful of examples of bifunctional RNA along with their functional roles.

AtTCTP2 mRNA and protein movement correlates with formation of adventitious roots in tobacco

The Translationally Controlled Tumor Proteins, or TCTP, is a superfamily of exclusively eukaryotic proteins essential in the regulation of proliferation and general growth. However, it is clear that these are multifunctional proteins given (1) the pleiotropic effects of its mutations, and (2), the multiple processes in which this protein is involved. TCTP function in general is conserved, since Arabidopsis AtTCTP1 can rescue a Drosophila mutant, and vice versa. It has become clear, however, that these proteins may have "taxon-specific" functions. In the case of plants, mRNA and/or proteins have been found in the phloem translocation stream of different species, suggesting a role in long-distance signaling. We have found that a second Arabidopsis TCTP gene, AtTCTP2, codes for a protein that moves long-distance through a graft union in tobacco. Interestingly, the mRNA is also transported long-distance. Both mRNA and protein move long-distance; interestingly, the movement, while more efficient from source to sink tissues, also occurs in the opposite direction. The protein reaches the nuclei of parenchyma cells and adventitious roots. Furthermore, it is clear that the long-distance delivery of AtTCTP2 protein and mRNA is required for the induction of adventitious roots. A model is presented that accounts for these observations.

Growth-factor dependent expression of the translationally controlled tumour protein TCTP is regulated through the PI3-K/Akt/mTORC1 signalling pathway

Translationally controlled tumour protein TCTP (gene symbol: TPT1) is a highly-conserved, cyto-protective protein implicated in many physiological and disease processes, in particular cancer, where it is associated with poor patient outcomes. To understand the mechanisms underlying the accumulation of high TCTP levels in cancer cells, we studied the signalling pathways that control translation of TCTP mRNA, which contains a 5'-terminal oligopyrimidine tract (5'-TOP). In HT29 colon cancer cells and in HeLa cells, serum increases the expression of TCTP two- and four-fold, respectively, and this is inhibited by rapamycin or mTOR kinase inhibitors. Polysome profiling and mRNA quantification indicate that these effects occur at the level of mRNA translation. Blocking this pathway upstream of mTOR complex 1 (mTORC1) by inhibiting Akt also prevented increases in TCTP levels in both HeLa and HT29 colon cancer cells, whereas knockout of TSC2, a negative regulator of mTORC1, led to derepression of TCTP synthesis under serum starvation. Overexpression of eIF4E enhanced the polysomal association of the TCTP mRNA, although it did not protect its translation from inhibition by rapamycin. Conversely, expression of a constitutively-active mutant of the eIF4E inhibitor 4E-BP1, which is normally inactivated by mTORC1, inhibited TCTP mRNA translation in HEK293 cells. Our results demonstrate that TCTP mRNA translation is regulated by signalling through the PI3-K/Akt/mTORC1 pathway. This explains why TCTP levels are frequently increased in cancers, since mTORC1 signalling is hyperactive in ~80% of tumours.

Expression of translationally controlled tumor protein in heat-stressed human dental pulp cells

OBJECTIVE

The aim of this study was to investigate the effects of heat stress on cell viability, translationally controlled tumor protein (TCTP) expression, and the effects of recombinant TCTP on heat-stressed human dental pulp cells (HDPCs).

METHODS

HDPCs were isolated from human teeth and cultured at 37°C. For heat stress, HPDCs were incubated at 43°C for 45min. After heat stress, recombinant TCTP were added to HDPCs and cultured for various periods of time at 37°C. Heat-treated cells were then analyzed by DNA staining with Hoechst 33258, MTT, and caspase 3 activity assays. TCTP expression level was assessed by real-time PCR and western blot analysis.

RESULTS

Heat-treated cells displayed lower cell density and nuclear morphology resembling apoptotic body. Heat stress significantly decreased cell viability and induced activity of caspase 3. The effect of recombinant TCTP on pulp cell death from heat stress varied depending on each subject and TCTP concentration. Heat stress up-regulated TCTP mRNA expression level. In contrast, TCTP protein level remained unchanged. Recombinant TCTP did not affect TCTP mRNA expression but down-regulated TCTP protein in heat-treated cells.

CONCLUSIONS

Heat stress induces caspase 3 activation and up-regulates TCTP mRNA expression in HDPCs. TCTP did not play a key role on pulp cell recovery from heat stress.

Telomerase activity and telomere length in Daphnia

Telomeres, comprised of short repetitive sequences, are essential for genome stability and have been studied in relation to cellular senescence and aging. Telomerase, the enzyme that adds telomeric repeats to chromosome ends, is essential for maintaining the overall telomere length. A lack of telomerase activity in mammalian somatic cells results in progressive shortening of telomeres with each cellular replication event. Mammals exhibit high rates of cell proliferation during embryonic and juvenile stages but very little somatic cell proliferation occurs during adult and senescent stages. The telomere hypothesis of cellular aging states that telomeres serve as an internal mitotic clock and telomere length erosion leads to cellular senescence and eventual cell death. In this report, we have examined telomerase activity, processivity, and telomere length in Daphnia, an organism that grows continuously throughout its life. Similar to insects, Daphnia telomeric repeat sequence was determined to be TTAGG and telomerase products with five-nucleotide periodicity were generated in the telomerase activity assay. We investigated telomerase function and telomere lengths in two closely related ecotypes of Daphnia with divergent lifespans, short-lived D. pulex and long-lived D. pulicaria. Our results indicate that there is no age-dependent decline in telomere length, telomerase activity, or processivity in short-lived D. pulex. On the contrary, a significant age dependent decline in telomere length, telomerase activity and processivity is observed during life span in long-lived D. pulicaria. While providing the first report on characterization of Daphnia telomeres and telomerase activity, our results also indicate that mechanisms other than telomere shortening may be responsible for the strikingly short life span of D. pulex.

The first characterization of gene structure and biological function for echinoderm translationally controlled tumor protein (TCTP)

Translationally controlled tumor protein (TCTP) is a multifunctional protein that existed ubiquitously in different eukaryote species and distributed widely in various tissues and cell types. In this study, the gene structure and biological function of TCTP were first characterized in echinoderm. An echinoderm TCTP named StmTCTP was identified from sea cucumber (Stichopus monotuberculatus) by expression sequence tag (EST) analysis and rapid amplification of cDNA ends (RACE) approach. The StmTCTP cDNA is 1219 bp in length, containing a 5'-untranslated region (UTR) of 77 bp, a 3'-UTR of 623 bp and an open reading frame (ORF) of 519 bp that encoding a protein of 172 amino acids with a deduced molecular weight of 19.80 kDa and a predicted isolectric point of 4.66. Two deduced signal signatures termed TCTP1 and TCTP2, a microtubule binding domain, a Ca(2+) binding domain and the conserved residues forming Rab GTPase binding surface were found in the StmTCTP amino acid sequence. For the gene structure, StmTCTP contains four exons separated by three introns. The anti-oxidation and heat shock protein activities of recombinant TCTP protein were also demonstrated in this study. In addition, the expression of StmTCTP was found to be significantly upregulated by polyriboinosinic polyribocytidylic acid [poly (I:C)], lipopolysaccharides (LPS) or inactivated bacteria challenge in in vitro primary culture experiments of coelomocytes, suggested that the sea cucumber TCTP might play critical roles not only in the defense against oxidative and thermal stresses, but also in the innate immune defense against bacterial and viral infections.

Ligand binding reveals a role for heme in translationally-controlled tumor protein dimerization

The translationally-controlled tumor protein (TCTP) is a highly conserved, ubiquitously expressed, abundant protein that is broadly distributed among eukaryotes. Its biological function spans numerous cellular processes ranging from regulation of the cell cycle and microtubule stabilization to cell growth, transformation, and death processes. In this work, we propose a new function for TCTP as a “buffer protein” controlling cellular homeostasis. We demonstrate that binding of hemin to TCTP is mediated by a conserved His-containing motif (His⁷⁶His⁷⁷) followed by dimerization, an event that involves ligand-mediated conformational changes and that is necessary to trigger TCTP's cytokine-like activity. Mutation in both His residues to Ala prevents hemin from binding and abrogates oligomerization, suggesting that the ligand site localizes at the interface of the oligomer. Unlike heme, binding of Ca²⁺ ligand to TCTP does not alter its monomeric state; although, Ca²⁺ is able to destabilize an existing TCTP dimer created by hemin addition. In agreement with TCTP's proposed buffer function, ligand binding occurs at high concentration, allowing the “buffer” condition to be dissociated from TCTP's role as a component of signal transduction mechanisms.

Nitazoxanide, an antiviral thiazolide, depletes ATP-sensitive intracellular Ca(2+) stores

Nitazoxanide (NTZ) inhibits influenza, Japanese encephalitis, hepatitis B and hepatitis C virus replication but effects on the replication of other members of the Flaviviridae family has yet to be defined. The pestivirus bovine viral diarrhoea virus (BVDV) is a surrogate model for HCV infection and NTZ induced PKR and eIF2α phosphorylation in both uninfected and BVDV-infected cells. This led to the observation that NTZ depletes ATP-sensitive intracellular Ca(2+) stores. In addition to PKR and eIF2α phosphorylation, consequences of NTZ-mediated Ca(2+) mobilisation included induction of chronic sub-lethal ER stress as well as perturbation of viral protein N-linked glycosylation and trafficking. To adapt to NTZ-mediated ER stress, NTZ treated cells upregulated translation of Ca(2+)-binding proteins, including the ER chaperone Bip and the cytosolic pro-survival and anti-viral protein TCTP. Depletion of intracellular Ca(2+) stores is the primary consequence of NTZ treatment and is likely to underpin all antiviral mechanisms attributed to the thiazolide.

Effect of novel chitosan-fluoroaluminosilicate resin modified glass ionomer cement supplemented with translationally controlled tumor protein on pulp cells

Dental materials that can promote cell proliferation and function is required for regenerative pulp therapy. Resin modified glass ionomer cement (RMGIC), a broadly used liner or restorative material, can cause apoptosis to pulp cells mainly due to HEMA (2-hydroxyethyl methacrylate), the released residual monomer. Recent studies found that chitosan and albumin could promote release of protein in GIC while translationally controlled tumor protein (TCTP) has an anti-apoptotic activity against HEMA. The aim of this study was to examine the effect of chitosan and albumin modified RMGIC (Exp-RMGIC) supplemented with TCTP on pulp cell viability and mineralization. Exp-RMGIC+TCTP was composed of RMGIC powder incorporated with 15 % of chitosan, 5 % albumin and supplemented with TCTP mixed with the same liquid components of RMGIC. The effect of each specimen on pulp cells was examined using the Transwell plate. From the MTT assay, Exp-RMGIC+TCTP had the highest percentages of viable cells (P < 0.05) at both 24 and 74 h. Flow cytometry revealed that, after 24 h, Exp-RMGIC+TCTP gave the lowest percentages of apoptotic cells compared to other groups. There was no difference in alkaline phosphatase (ALP) activity among different formula of the specimens, while cells cultured in media with TCTP had higher ALP activity. Von Kossa staining revealed that RMGIC+TCTP, and Exp-RMGIC+TCTP had higher percentages of calcium deposit area compared to those without TCTP. It was concluded that Exp-RMGIC supplemented with TCTP had less cytotoxicity than RMGIC and can protect cells from apoptosis better than RMGIC supplemented with TCTP.

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.

Structural divergence of plant TCTPs

The Translationally Controlled Tumor Protein (TCTP) is a highly conserved protein at the level of sequence, considered to play an essential role in the regulation of growth and development in eukaryotes. However, this function has been inferred from studies in a few model systems, such as mice and mammalian cell lines, Drosophila and Arabidopsis. Thus, the knowledge regarding this protein is far from complete. In the present study bioinformatic analysis showed the presence of one or more TCTP genes per genome in plants with highly conserved signatures and subtle variations at the level of primary structure but with more noticeable differences at the level of predicted three-dimensional structures. These structures show differences in the "pocket" region close to the center of the protein and in its flexible loop domain. In fact, all predictive TCTP structures can be divided into two groups: (1) AtTCTP1-like and (2) CmTCTP-like, based on the predicted structures of an Arabidopsis TCTP and a Cucurbita maxima TCTP; according to this classification we propose that their probable function in plants may be inferred in principle. Thus, different TCTP genes in a single organism may have different functions; additionally, in those species harboring a single TCTP gene this could carry multiple functions. On the other hand, in silico analysis of AtTCTP1-like and CmTCTP-like promoters suggest that these share common motifs but with different abundance, which may underscore differences in their gene expression patterns. Finally, the absence of TCTP genes in most chlorophytes with the exception of Coccomyxa subellipsoidea, indicates that other proteins perform the roles played by TCTP or the pathways regulated by TCTP occur through alternative routes. These findings provide insight into the evolution of this gene family in plants.

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.

The response profiles of HSPA12A and TCTP from Mytilus galloprovincialis to pathogen and cadmium challenge

Heat shock 70 kDa protein 12A (HSPA12A) is an atypical member of HSP70 family, and the translationally controlled tumor protein (TCTP) is a novel HSP with chaperone-like activity. They are both involved in protecting organisms against various stressors. In the present study, the cDNAs of HSPA12A and TCTP (called MgHSPA12A and MgTCTP) were identified from Mytilus galloprovincialis by RACE approaches. The full-length cDNA of MgHSPA12A and MgTCTP encoded a peptide of 491 and 171 amino acids, respectively. Real-time PCR was employed to analyze the tissue distribution and temporal expression of these two genes after bacterial challenge and cadmium (Cd) exposure. It was found that the transcripts of MgHSPA12A and MgTCTP were dominantly expressed in gonad and muscle, respectively. The expression level of MgTCTP at 48 h post Vibrio anguillarum challenge was detected to be significantly up-regulated in hepatopancreas (P < 0.05). As concerned to Cd exposure, 2.0-fold increase of MgHSPA12A expression compared to that of the control was observed at 48 h in 5 μg/L Cd(2+)-treated group, while the expression levels of MgTCTP were significantly decreased after exposed to both 5 and 50 μg/L Cd(2+) for 24 h and 96 h. These results suggested the potential involvement of MgHSPA12A and MgTCTP in the mediation of the immune responses and environmental stress in mussels.

TCTP is an androgen-regulated gene implicated in prostate cancer

TCTP has been implicated in a plethora of important cellular processes related to cell growth, cell cycle progression, malignant transformation and inhibition of apoptosis. In addition to these intracellular functions, TCTP has extracellular functions and plays an important role in immune cells. TCTP expression was previously shown to be deregulated in prostate cancer, but its function in prostate cancer cells is largely unknown. Here we show that TCTP expression is regulated by androgens in LNCaP prostate cancer cells in vitro as well as human prostate cancer xenografts in vivo. Knockdown of TCTP reduced colony formation and increased apoptosis in LNCaP cells, implicating it as an important factor for prostate cancer cell growth. Global gene expression profiling in TCTP knockdown LNCaP cells showed that several interferon regulated genes are regulated by TCTP, suggesting that it may have a role in regulating immune function in prostate cancer. In addition, recombinant TCTP treatment increased colony formation in LNCaP cells suggesting that secreted TCTP may function as a proliferative factor in prostate cancer. These results suggest that TCTP may have a role in prostate cancer development.

Regulatory Roles for Long ncRNA and mRNA

Recent advances in high-throughput sequencing technology have identified the transcription of a much larger portion of the genome than previously anticipated. Especially in the context of cancer it has become clear that aberrant transcription of both protein-coding and long non-coding RNAs (lncRNAs) are frequent events. The current dogma of RNA function describes mRNA to be responsible for the synthesis of proteins, whereas non-coding RNA can have regulatory or epigenetic functions. However, this distinction between protein coding and regulatory ability of transcripts may not be that strict. Here, we review the increasing body of evidence for the existence of multifunctional RNAs that have both protein-coding and trans-regulatory roles. Moreover, we demonstrate that coding transcripts bind to components of the Polycomb Repressor Complex 2 (PRC2) with similar affinities as non-coding transcripts, revealing potential epigenetic regulation by mRNAs. We hypothesize that studies on the regulatory ability of disease-associated mRNAs will form an important new field of research.

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.

Redox proteomics in selected neurodegenerative disorders: from its infancy to future applications

Several studies demonstrated that oxidative damage is a characteristic feature of many neurodegenerative diseases. The accumulation of oxidatively modified proteins may disrupt cellular functions by affecting protein expression, protein turnover, cell signaling, and induction of apoptosis and necrosis, suggesting that protein oxidation could have both physiological and pathological significance. For nearly two decades, our laboratory focused particular attention on studying oxidative damage of proteins and how their chemical modifications induced by reactive oxygen species/reactive nitrogen species correlate with pathology, biochemical alterations, and clinical presentations of Alzheimer's disease. This comprehensive article outlines basic knowledge of oxidative modification of proteins and lipids, followed by the principles of redox proteomics analysis, which also involve recent advances of mass spectrometry technology, and its application to selected age-related neurodegenerative diseases. Redox proteomics results obtained in different diseases and animal models thereof may provide new insights into the main mechanisms involved in the pathogenesis and progression of oxidative-stress-related neurodegenerative disorders. Redox proteomics can be considered a multifaceted approach that has the potential to provide insights into the molecular mechanisms of a disease, to find disease markers, as well as to identify potential targets for drug therapy. Considering the importance of a better understanding of the cause/effect of protein dysfunction in the pathogenesis and progression of neurodegenerative disorders, this article provides an overview of the intrinsic power of the redox proteomics approach together with the most significant results obtained by our laboratory and others during almost 10 years of research on neurodegenerative disorders since we initiated the field of redox proteomics.

TPT1/ TCTP-regulated pathways in phenotypic reprogramming

Evolutionary conserved and pleiotropic, the TPT1/TCTP gene (translationally controlled tumor protein, also called HRF, fortilin), encodes a highly structured mRNA shielded by ribonucleoproteins and closely resembling viral particles. This mRNA activates, as do viruses, protein kinase R (PKR). The TPT1/TCTP protein is structurally similar to mRNA-helicases and MSS4. TPT1/TCTP has recently been identified as a prognostic factor in breast cancer and a critical regulator of the tumor suppressor p53 and of the cancer stem cell (SC) compartment. Emerging evidence indicates that TPT1/TCTP is key to phenotypic reprogramming, as shown in the process of tumor reversion and possibly in pluripotency. We provide here an overview of these diverse functions of TPT1/TCTP.

TCTP in development and cancer

The translationally controlled tumor protein (TCTP) is highly conserved among animal species. It is widely expressed in many different tissues. It is involved in regulating many fundamental processes, such as cell proliferation and growth, apoptosis, pluripotency, and the cell cycle. Hence, it is not surprising that it is essential for normal development and, if misregulated, can lead to cancer. Provided herein is an overview of the diverse functions of TCTP, with a focus on development. Furthermore, we discuss possible ways by which TCTP misregulation or mutation could result in cancer.

Role of translationally controlled tumor protein in cancer progression

Translationally controlled tumor protein (TCTP) is a highly conserved and ubiquitously expressed protein in all eukaryotes-highlighting its important functions in the cell. Previous studies revealed that TCTP is implicated in many biological processes, including cell growth, tumor reversion, and induction of pluripotent stem cell. A recent study on the solution structure from fission yeast orthologue classifies TCTP under a family of small chaperone proteins. There is growing evidence in the literature that TCTP is a multifunctional protein and exerts its biological activity at the extracellular and intracellular levels. Although TCTP is not a tumor-specific protein, our research group, among several others, focused on the role(s) of TCTP in cancer progression. In this paper, we will summarize the current scientific knowledge of TCTP in different aspects, and the precise oncogenic mechanisms of TCTP will be discussed in detail.

Translationally controlled tumour protein is associated with podocyte hypertrophy in a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

Translationally controlled tumour protein (TCTP) is thought to be involved in cell growth by regulating mTOR complex 1 (mTORC1) signalling. As diabetes characteristically induces podocyte hypertrophy and mTORC1 has been implicated in this process, TCTP may have a role in the pathogenesis of diabetes-induced podocyte hypertrophy.

METHODS

We investigated the effects and molecular mechanisms of TCTP in diabetic mice and in high glucose-stimulated cultured podocytes. To characterise the role of TCTP, we conducted lentivirus-mediated gene silencing of TCTP both in vivo and in vitro.

RESULTS

Glomerular production of TCTP was significantly higher in streptozotocin induced-diabetic DBA/2J mice than in control animals. Double-immunofluorescence staining for TCTP and synaptopodin revealed that podocyte was the principal cell responsible for this increase. TCTP knockdown attenuated the activation of mTORC1 downstream effectors and the overproduction of cyclin-dependent kinase inhibitors (CKIs) in diabetic glomeruli, along with a reduction in proteinuria and a decrease in the sizes of podocytes as well as glomeruli. In addition, knockdown of TCTP in db/db mice prevented the development of diabetic nephropathy, as indicated by the amelioration of proteinuria, mesangial expansion, podocytopenia and glomerulosclerosis. In accordance with the in vivo data, TCTP inhibition abrogated high glucose-induced hypertrophy in cultured podocytes, which was accompanied by the downregulation of mTORC1 effectors and CKIs.

CONCLUSIONS/INTERPRETATION

These findings suggest that TCTP might play an important role in the process of podocyte hypertrophy under diabetic conditions via the regulation of mTORC1 activity and the induction of cell-cycle arrest.

Comparative proteomic study and functional analysis of translationally controlled tumor protein in rice roots under Hg2+ stress

So far, very little is known about mercury stress-induced intercellular metabolic changes in rice roots at the proteome level. To investigate the response of rice roots to mercury stress, changes in protein expression in rice roots were analyzed using a comparative proteomics approach. Six-leaf stage rice seedlings were treated with 50 micromol/L HgCl2 for 3 hr; 29 protein spots showed a significant changes in abundance under stress when compared with the Hg2+ -tolerant rice mutant and wild type (Zhonghua 11). Furthermore, all these protein spots were identified by mass spectrometry to match 27 diverse protein species. The identified proteins were involved in several processes, including stress response, redox homeostasis, signal transduction, regulation and metabolism; some were found to be cellular structure proteins and a few were unknown. Among the up-regulated proteins, OsTCTP (translationally controlled tumor protein) was chosen to perform hetereologous expression in yeast which was presumed to participate in the Hg2+ tolerance of rice, providing evidence for its role in alleviating Hg2+ damage. Among the many tests, we found that OsTCTP-overexpressed yeast strains were more resistant to Hg2+ than wild-type yeast. Thus, we propose that OsTCTP contributes to Hg2+ resistance. Here we present, for the first time, the functional characterization of OsTCTP in connection with Hg2+ stress in plants.

Reciprocal repression between P53 and TCTP

Screening for genes that reprogram cancer cells for the tumor reversion switch identified TCTP (encoding translationally controlled tumor protein) as a crucial regulator of apoptosis. Here we report a negative feedback loop between P53 and TCTP. TCTP promotes P53 degradation by competing with NUMB for binding to P53-MDM2-containing complexes. TCTP inhibits MDM2 auto-ubiquitination and promotes MDM2-mediated ubiquitination and degradation of P53. Notably, Tctp haploinsufficient mice are sensitized to P53-dependent apoptosis. In addition, P53 directly represses TCTP transcription. In 508 breast cancers, high-TCTP status associates with poorly differentiated, aggressive G3-grade tumors, predicting poor prognosis (P < 0.0005). Tctp knockdown in primary mammary tumor cells from ErbB2 transgenic mice results in increased P53 expression and a decreased number of stem-like cancer cells. The pharmacological compounds sertraline and thioridazine increase the amount of P53 by neutralizing TCTP's action on the MDM2-P53 axis. This study links TCTP and P53 in a previously unidentified regulatory circuitry that may underlie the relevance of TCTP in cancer.

Proteomic analysis of tumor tissue in CT-26 implanted BALB/C mouse after treatment with ascorbic acid

Tumor establishment and penetration consists of a series of complex processes involving multiple changes in gene expression and protein modification. Proteome changes of tumor tissue were investigated after intraperitoneal administration of a high concentration of ascorbic acid in BALB/C mice implanted with CT-26 cancer cells using two-dimensional gel electrophoresis and mass spectrometry. Eighteen protein spots were identified whose expression was different between control and ascorbic acid treatment groups. In particular, eukaryotic translation initiation factor 3 subunit 1, nucleophosmin, latexin, actin-related protein 2/3 complex subunit 5, M2-type pyruvate kinase, vimentin, tumor protein translationally-controlled 1, RAS oncogene family Ran, plastin 3 precursor, ATPase, Rho GDT dissociation inhibitor β, and proteasome activator subunit 2 expression were quantitatively up-regulated. The increase in the level of these proteins was accompanied by an increase in mRNA level. The cytoskeleton protein actin, vimentin, and tumor protein translationally-controlled 1 showed quantitative expression profile differences. A change in actin cytoskeleton distribution, functionally relevant to the proteome result, was observed after treatment with ascorbic acid. These results suggest a previously undefined role of ascorbic acid in the regulation of cytoskeleton remodeling in tumor tissues.

Histamine-releasing factor has a proinflammatory role in mouse models of asthma and allergy

IgE-mediated activation of mast cells and basophils underlies allergic diseases such as asthma. Histamine-releasing factor (HRF; also known as translationally controlled tumor protein [TCTP] and fortilin) has been implicated in late-phase allergic reactions (LPRs) and chronic allergic inflammation, but its functions during asthma are not well understood. Here, we identified a subset of IgE and IgG antibodies as HRF-interacting molecules in vitro. HRF was able to dimerize and bind to Igs via interactions of its N-terminal and internal regions with the Fab region of Igs. Therefore, HRF together with HRF-reactive IgE was able to activate mast cells in vitro. In mouse models of asthma and allergy, Ig-interacting HRF peptides that were shown to block HRF/Ig interactions in vitro inhibited IgE/HRF-induced mast cell activation and in vivo cutaneous anaphylaxis and airway inflammation. Intranasally administered HRF recruited inflammatory immune cells to the lung in naive mice in a mast cell- and Fc receptor-dependent manner. These results indicate that HRF has a proinflammatory role in asthma and skin immediate hypersensitivity, leading us to suggest HRF as a potential therapeutic target.

A novel TCTP gene from the crustacean Eriocheir sinensis: possible role involving metallic Cu2+ stress

The translationally controlled tumor protein (TCTP), which was initially described as a growth-related protein, primarily expresses proteins for numerous biological processes in eukaryotes. In the present study, the TCTP gene in the Chinese mitten crab Eriocheir sinensis (Es-TCTP) was identified from tissues of the hepatopancreas, by the construction of a cDNA library and the rapid amplification of cDNA ends. The results showed that the full length of Es-TCTP cDNA comprises 727 nucleotides, with an open reading frame of 507 bp that encodes 168 amino acid residues. The deduced amino acid sequence of Es-TCTP has a 51%-92% similarity to TCTPs of other eukaryotic species. The mRNA transcripts of Es-TCTP were detected by using RT-PCR for all tissues, with the highest level occurring in the hepatopancreas. In addition, temporal expression of the Es-TCTP was measured to analyze the role of Es-TCTP in an acute stress condition after CuSO(4) treatment. The expression of the Es-TCTP transcripts in hepatopancreas had no significant difference at the first 4 h, but increased significantly after 8 h, peaked at 24 h (4.3-fold higher than the control), and was still high after 72 h. Our results indicate that Es-TCTP is an acute-phase protein that is involved in Cu(2+) stress, with a possible anti-stress function in invertebrates.

Expression of translationally controlled tumor protein (TCTP) in the uterus of mice of early pregnancy and its possible significance during embryo implantation

BACKGROUND

Translationally controlled tumor protein (TCTP) is a highly conserved, growth-related protein. Previous studies showed that TCTP is involved in many biological processes and it is essential for early embryo development and proliferation of embryonic stem cells. However, whether TCTP plays a role during embryo implantation remains unclear. This paper examines the expression and the role of TCTP in the uterus of mice during early pregnancy.

METHODS

The expression of TCTP in the uterus of mice during early pregnancy was examined by quantitative real-time PCR, immunohistochemistry and western blot. A functional study of TCTP in embryo implantation of mice was also performed by intrauterine injection with antisense oligodeoxynucleotides (A-ODNs) of TCTP on day 3 (D3) of pregnancy.

RESULTS

The TCTP mRNA levels were significantly upgraded from D3 to D5 of pregnancy and reached maximum levels on D5, then dramatically decreased on D6 and D7. The levels of the TCTP protein detected by western blot were consistent with those of the mRNA. Immunohistochemistry analysis showed that the TCTP protein was mainly located in the luminal and the glandular epithelium on D1 and D2 of pregnancy and reached maximum levels on D5 in the luminal and glandular epithelium and in the stromal cells. The levels of TCTP in the pseudo-pregnant uterus of mice were lower than those of pregnant mice on D4 and D6. Furthermore, inhibiting the TCTP expression by intrauterine injection with A-ODNs of TCTP on D3 of pregnancy significantly reduced the number of the implanted embryos compared with the control.

CONCLUSIONS

This study demonstrated that TCTP may play a significant role in embryo implantation in mice.