The chemistry and biology of thymosin. II. Amino acid sequence analysis of thymosin alpha1 and polypeptide beta1

Simulated Gastrointestinal Digestion Enhances the Immunomodulatory Activity of Ovalbumin Peptide NVMEERKIK: Mechanistic Insights into TLR4/MAPK/NF-κB Signaling Modulation

NVMEERKIK, a peptide derived from ovalbumin, exhibited remarkable immunomodulatory activity. This study investigated the effect of simulated gastrointestinal digestion on its structure and bioactivity. NVMEERKIK was found to be unstable against gastrointestinal enzymes and completely degraded into NVME, NVMEE, KIK, K, and R. Among these, NVME, which constituted 90.90% of the digest, was synthesized and demonstrated a superior immune-enhancing activity than NVMEERKIK. Specifically, NVME improved phagocytosis, NO production, and TNF-α content in RAW264.7 cells by 1.31-15.86%, 17.17-122.08%, and 0.36-16.76%, respectively. TLR4 inhibition and immunofluorescence assays revealed the strong TLR4 activation and recognition capacities of both peptides. Furthermore, the Western blot results showed that NVMEERKIK and NVME activated the MAPK/NF-κB pathway by upregulating ERK, JNK, p38, and p65, leading to enhanced activation of RAW264.7 cells. The improved immune-enhancing activity of NVMEERKIK after digestion highlighted its potential as an immunomodulatory peptide for functional food applications.

Robust Chemical Synthesis of "Difficult Peptides" via 2-Hydroxyphenol-pseudoproline (ψ2-hydroxyphenolpro) Modifications

The challenging preparation of "difficult peptides" has always hindered the development of peptide-active pharmaceutical ingredients. Pseudoproline (ψpro) building blocks have been proven effective and powerful tools for the synthesis of "difficult peptides". In this paper, we efficiently prepared a set of novel 2-(oxazolidin-2-yl)phenol compounds as proline surrogates (2-hydroxyphenol-pseudoprolines, ψ2-hydroxyphenolpro) and applied it in the synthesis of many well-known "difficult peptides", including human thymosin α1, amylin, and β-amyloid (1-42) (Aβ42).

Thymosin α1 and Its Role in Viral Infectious Diseases: The Mechanism and Clinical Application

Thymosin α1 (Tα1) is an immunostimulatory peptide that is commonly used as an immune enhancer in viral infectious diseases such as hepatitis B, hepatitis C, and acquired immune deficiency syndrome (AIDS). Tα1 can influence the functions of immune cells, such as T cells, B cells, macrophages, and natural killer cells, by interacting with various Toll-like receptors (TLRs). Generally, Tα1 can bind to TLR3/4/9 and activate downstream IRF3 and NF-κB signal pathways, thus promoting the proliferation and activation of target immune cells. Moreover, TLR2 and TLR7 are also associated with Tα1. TLR2/NF-κB, TLR2/p38MAPK, or TLR7/MyD88 signaling pathways are activated by Tα1 to promote the production of various cytokines, thereby enhancing the innate and adaptive immune responses. At present, there are many reports on the clinical application and pharmacological research of Tα1, but there is no systematic review to analyze its exact clinical efficacy in these viral infectious diseases via its modulation of immune function. This review offers an overview and discussion of the characteristics of Tα1, its immunomodulatory properties, the molecular mechanisms underlying its therapeutic effects, and its clinical applications in antiviral therapy.

Thymosin α-1 in cancer therapy: Immunoregulation and potential applications

Thymosin α-1 (Tα-1) is an immunomodulating polypeptide of 28 amino acids, which was the first peptide isolated from thymic tissue and has been widely used for the treatment of viral infections, immunodeficiencies, and especially malignancies. Tα-1 stimulates both innate and adaptive immune responses, and its regulation of innate immune cells and adaptive immune cells varies under different disease conditions. Pleiotropic regulation of immune cells by Tα-1 depends on activation of Toll-like receptors and its downstream signaling pathways in various immune microenvironments. For treatment of malignancies, the combination of Tα-1 and chemotherapy has a strong synergistic effect by enhancing the anti-tumor immune response. On the basis of the pleiotropic effect of Tα-1 on immune cells and the promising results of preclinical studies, Tα-1 may be a favorable immunomodulator to enhance the curative effect and decrease immune-related adverse events of immune checkpoint inhibitors to develop novel cancer therapies.

Improvement in cognitive dysfunction following blast induced traumatic brain injury by thymosin α1 in rats: Involvement of inhibition of tau phosphorylation at the Thr205 epitope

Cognitive impairment is a significant sequela of traumatic brain injury (TBI) especially blast induced traumatic brain injury (bTBI), which is characterized by rapid impairments of learning and memory ability. Although several neuroprotective agents have been postulated as promising drugs for bTBI in animal studies, very few ideal therapeutic options exist to improve cognitive impairment following bTBI. Thymosin α1(Tα1), a 28-amino-acid protein that possesses immunomodulatory functions, has exhibited beneficial effects in the treatment of infectious diseases, immunodeficiency diseases and cancers. However, it remains unclear whether Tα1 has a therapeutic role in bTBI. Thus, we hypothesized that Tα1 administration could reverse the outcomes of bTBI. The blast induced TBI (bTBI) rat model was established with the compressed gas driven blast injury model system. A consecutive Tα1 therapy (in 1 ml saline, twice a day) at a dose of 200 µg/kg or normal saline (NS) (1 ml, twice a day) for 3 days or 2 weeks was performed. Utilizing our newly designed bTBI model, we investigated the beneficial effects of Tα1 therapy on rats exposed to bTBI including: cognitive functions, general histology, regulatory T (Treg) cells, edema, inflammation reactions and the expression and phosphorylation level of tau via Morris Water Maze test (MWM test), HE staining, flow cytometry, brain water content (BWC) calculation, IL-6 assay and Western blotting, respectively. Tα1 treatment seemed to reduce the 24-hour mortality, albeit with no statistical significance. Moreover, Tα1 treatment markedly improved cognitive dysfunction by decreasing the escape latency in the acquisition phase, and increasing the crossing numbers in the probe phase of MWM test. More interestingly, Tα1 significantly inhibited tau phosphorylation at the Thr205 epitope, but not at the Ser404 and Ser262 epitopes. Tα1 increased the percentage of Treg cells and inhibited plasma IL-6 production on 3d post bTBI. Moreover, Tα1 suppressed brain edema as demonstrated by decrease of BWC. However, there was a lack of obvious change in histopathology in the brain upon Tα1 treatment. This is the first study showing that Tα1 improves neurological deficits after bTBI in rats, which is potentially related to the inhibition of tau phosphorylation at the Thr205 epitope, increased Treg cells and decreased inflammatory reactions and brain edema.

Thymosin alpha 1 treatment for patients with sepsis

INTRODUCTION

Sepsis is a life-threatening organ dysfunction caused by host immune response to infection. In this regard, modifying host immune response may help to eliminate systemic infection and restore organ function. Thymosin alpha 1 (Tα1), acting as an immune modulator, exerts great biological influence in activating and restoring the dysregulated immune response for patients with sepsis.

AREAS COVERED

In this review, we summarize the clinical studies of Tα1 treatment alone and in combination with anti-inflammatory for patients with sepsis or septic shock. Clinical studies were collected from available English and Chinese databases.

EXPERT OPINION

In previous studies, single or combined treatment with Tα1 reduced the mortality rate of sepsis, improved the expression of HLA-DR on monocyte, and diminished the incidence of secondary infection. Based on the existing studies, Tα1 seems to be a promising alternative adjuvant therapy for sepsis. However, sepsis is a remarkably heterogeneous clinical syndrome, so much so that it is impossible to generalize the clinical results to all septic patients. Also, the present studies on Tα1 treatment are not able to focus on the immunosuppressive individuals. We believe that selecting septic patients with immunosuppression will be more likely to reveal the efficacy of Tα1 in future trials.

Serum thymosin alpha 1 levels in normal and pathological conditions

INTRODUCTION

Thymosin alpha 1 (Ta1) is a natural occurring peptide hormone that is crucial for the maintenance of the organism homeostasis. It has been chemically synthesized and used in diseases where the immune system is hindered or malfunctioning.

AREAS COVERED

Many clinical trials investigate the Ta1 effects in patients with cancer, infectious diseases and as a vaccine enhancer. The number of diseases that could benefit from Ta1 treatment is increasing. To date, questions remain about the physiological basal levels of Ta1 and the most effective dose and schedule of treatment. Evidence is growing that diseases characterized by deregulation of immune and/or inflammatory responses are associated with serum levels of Ta1 significantly lower than those of healthy individuals: to date, B hepatitis, psoriatic arthritis, multiple sclerosis and sepsis. The sputum of cystic fibrosis patients contains lower levels of Ta1 than healthy controls. These data are consistent with the role of Ta1 as a regulator of immunity, tolerance and inflammation.

EXPERT OPINION

Low serum Ta1 levels are predictive and/or associated with different pathological conditions. In case of Ta1 treatment, it is crucial to know the patient's baseline serum Ta1 level to establish effective treatment protocols and monitor their effectiveness over time.

Thymosin fraction 5 re-evaluated after 35 years by high-resolution mass spectrometry

OBJECTIVES

We reevaluated a lyophilized sample of thymosin fraction 5, stored for 37 years at room temperature, by high-resolution mass spectrometry in terms of stability and yet uncharacterized polypeptides that could be biological important substances.

METHODS

A top-down proteomic platform based on high-performance liquid chromatography (HPLC) coupled to high-resolution LTQ-Orbitrap mass spectrometry (MS) was applied to molecular characterization of polypeptides present in thymosin fraction 5.

RESULTS

We detected more than 100 monoisotopic masses corresponding to thymosin β4 and truncated forms of ubiquitin, prothymosin α, thymosin β4, and thymosin β9. Additionally, we discovered a new polypeptide present in thymosin fraction 5 and identified it as intact SH3 domain-binding glutamic acid-rich-like protein 3.

CONCLUSION

In spite of the well-known proteolytic processes inherent to the preparation of thymosin fraction 5, still uncharacterized polypeptides as well as truncated forms of already well-known thymosins are present in fraction 5 after long-term storage. Therefore, continuing characterization of thymosin fraction 5 is even nowadays highly promising.

Optically-Monitored Nanopore Fabrication Using a Focused Laser Beam

Solid-state nanopores (ssNPs) are extremely versatile single-molecule sensors and their potential have been established in numerous biomedical applications. However, the fabrication of ssNPs remains the main bottleneck to their widespread use. Herein, we introduce a rapid and localizable ssNPs fabrication method based on feedback-controlled optical etching. We show that a focused blue laser beam irreversibly etches silicon nitride (SiN_x) membranes in solution. Furthermore, photoluminescence (PL) emitted from the SiN_x is used to monitor the etching process in real-time, hence permitting rate adjustment. Transmission electron microscopy (TEM) images of the etched area reveal an inverted Gaussian thickness profile, corresponding to the intensity point spread function of the laser beam. Continued laser exposure leads to the opening of a nanopore, which can be controlled to reproducibly fabricate nanopores of different sizes. The optically-formed ssNPs exhibit electrical noise on par with TEM-drilled pores, and translocate DNA and proteins readily. Notably, due to the localized thinning, the laser-drilled ssNPs exhibit highly suppressed background PL and improved spatial resolution. Given the total control over the nanopore position, this easily implemented method is ideally suited for electro-optical sensing and opens up the possibility of fabricating large nanopore arrays in situ.

Effects of overexpression and inhibited expression of thymosin, an actin-interacting protein from Bombyx mori, on BmNPV proliferation and replication

Previous study showed that exogenously applied recombinant thymosin from Bombyx mori (BmTHY) reduces B. mori nucleopolyhedrovirus (BmNPV) proliferation in silkworm. Which stands to reason that BmTHY in B. mori is crucial for the defense against BmNPV. However, little is known about the effect of endogenously overexpressed or repressed BmTHY on B. mori resistance to virus infection. To study this issue, we constructed an overexpression and inhibited expression systems of BmTHY in BmN cells. The viral titer and the analysis from the quantitative real-time polymerase chain reaction (PCR) revealed that overexpression of BmTHY decreased the copies of BmNPV gene gp41, which goes over to inhibit the proliferation of BmNPV in BmN cells, while the inhibited expression of BmTHY significantly enhanced viral proliferation in infected BmN cells. These results indicated that endogenous BmTHY can inhibit BmNPV proliferation and replication in infected BmN cells. Furthermore, Co-IP showed that BmTHY could bind to actin in BmN cells. Also, the overexpression or inhibited expression of BmTHY shifted the ratio of F/G-actin in infected BmN cells. Lastly, the BmTHY, an actin-interacting protein, might be one of the key host factors against BmNPV, which inhibits viral proliferation and replication in BmN cells.

Thymosin α1 Interacts with Hyaluronic Acid Electrostatically by Its Terminal Sequence LKEKK

Thymosin α1 (Tα1), is a peptidic hormone, whose immune regulatory properties have been demonstrated both in vitro and in vivo and approved in different countries for treatment of several viral infections and cancers. Tα1 assumes a conformation in negative membranes upon insertion into the phosphatidylserine exposure as found in several pathologies and in apoptosis. These findings are in agreement with the pleiotropy of Tα1, which targets both normal and tumor cells, interacting with multiple cellular components, and have generated renewed interest in the topic. Hyaluronan (HA) occurs ubiquitously in the extracellular matrix and on cell surfaces and has been related to a variety of diseases, and developmental and physiological processes. Proteins binding HA, among them CD44 and the Receptor for HA-mediated motility (RHAMM) receptors, mediate its biological effects. NMR spectroscopy indicated preliminarily that an interaction of Tα1 with HA occurs specifically around lysine residues of the sequence LKEKK of Tα1 and is suggestive of a possible interference of Tα1 in the binding of HA with CD44 and RHAMM. Further studies are needed to deepen these observations because Tα1 is known to potentiate the T-cell immunity and anti-tumor effect. The binding inhibitory activity of Tα1 on HA-CD44 or HA-RHAMM interactions can suppress both T-cell reactivity and tumor progression.

Thymosin From Bombyx mori Is Down-Regulated in Expression by BmNPV Exhibiting Antiviral Activity

Thymosins have been highly conserved during evolution. These hormones exist in many animal species and play an essential role in many biological events. However, little is known regarding the physiological function of silkworm Bombyx mori thymosin (BmTHY). In this study, we investigated the expression pattern of BmTHY in a Bombyx mori larval ovarian cell line (BmN) challenged with Bombyx mori nuclear polyhydrosis virus (BmNPV) and the antiviral effect of recombinant BmTHY (rBmTHY) for Bombyx mori against BmNPV. Western-blot assay and qRT-PCR analysis revealed that the level of BmTHY protein expression and transcription decreased over time when BmN cells were infected by BmNPV. Treatment with endotoxin-free rBmTHY led to a significant reduction in viral titer in the supernatant of BmN cells challenged with BmNPV. The results from antiviral tests performed in vitro and in vivo showed that endotoxin-free rBmTHY improved the survival rate of Bombyx mori infected with BmNPV. These findings suggest that BmTHY exerts immunomodulatory effects on Bombyx mori, rendering them resistant to viral infection.

Immune Modulation with Thymosin Alpha 1 Treatment

Thymosin alpha 1 (Ta1) is a peptide originally isolated from thymic tissue as the compound responsible for restoring immune function to thymectomized mice. Ta1 has a pleiotropic mechanism of action, affecting multiple immune cell subsets that are involved in immune suppression. Ta1 acts through Toll-like receptors in both myeloid and plasmacytoid dendritic cells, leading to activation and stimulation of signaling pathways and initiation of production of immune-related cytokines. Due to the immune stimulating effects of Ta1, the compound would be expected to show utility for treatment of immune suppression, whether related to aging or to diseases such as infection or cancer. Extensive studies in both the preclinical and clinical setting will be summarized in the subsequent sections. These studies have demonstrated improvements in immune system cell subsets and the potential of Ta1 for the treatment of a range of diseases.

Mechanism of Action of Thymosinα1: Does It Interact with Membrane by Recognition of Exposed Phosphatidylserine on Cell Surface? A Structural Approach

Thymosinα1 is a peptidic hormone with pleiotropic activity, which is used in the therapy of several diseases. It is unstructured in water solution and interacts with negative regions of micelles and vesicles assuming two tracts of helical conformation with a structural flexible break in between. The studies of the interaction of Thymosinα1 with micelles of mixed dipalmitoylphosphatidylcholine and sodium dodecylsulfate and vesicles with mixed dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylserine, the latter the negative component of the membranes, by (1)H and natural abundance (15)N NMR are herewith reported, reviewed, and discussed. The results indicate that the preferred interactions are those where the surface is negatively charged due to sodium dodecylsulfate or due to the presence of dipalmitoylphosphatidylserine exposed on the surface. In fact the unbalance of dipalmitoylphosphatidylserine on the cellular surface is an important phenomenon present in pathological conditions of cells. Moreover, the direct interaction of Thymosinα1 with K562 cells presenting an overexposure of phosphatidylserine as a consequence of resveratrol-induced apoptosis was carried out.

Direct Sensing and Discrimination among Ubiquitin and Ubiquitin Chains Using Solid-State Nanopores

Nanopore sensing involves an electrophoretic transport of analytes through a nanoscale pore, permitting label-free sensing at the single-molecule level. However, to date, the detection of individual small proteins has been challenging, primarily due to the poor signal/noise ratio that these molecules produce during passage through the pore. Here, we show that fine adjustment of the buffer pH, close to the isoelectric point, can be used to slow down the translocation speed of the analytes, hence permitting sensing and characterization of small globular proteins. Ubiquitin (Ub) is a small protein of 8.5 kDa, which is well conserved in all eukaryotes. Ub conjugates to proteins as a posttranslational modification called ubiquitination. The immense diversity of Ub substrates, as well as the complexity of Ub modification types and the numerous physiological consequences of these modifications, make Ub and Ub chains an interesting and challenging subject of study. The ability to detect Ub and to identify Ub linkage type at the single-molecule level may provide a novel tool for investigation in the Ub field. This is especially adequate because, for most ubiquitinated substrates, Ub modifies only a few molecules in the cell at a given time. Applying our method to the detection of mono- and poly-Ub molecules, we show that we can analyze their characteristics using nanopores. Of particular importance is that two Ub dimers that are equal in molecular weight but differ in 3D structure due to their different linkage types can be readily discriminated. Thus, to our knowledge, our method offers a novel approach for analyzing proteins in unprecedented detail using solid-state nanopores. Specifically, it provides the basis for development of single-molecule sensing of differently ubiquitinated substrates with different biological significance. Finally, our study serves as a proof of concept for approaching nanopore detection of sub-10-kDa proteins and demonstrates the ability of this method to differentiate among native and untethered proteins of the same mass.

Historical review on thymosin α1 in oncology: preclinical and clinical experiences

INTRODUCTION

Thymosin α1 (Tα1) is a naturally occurring polypeptide that regulates immune cell development and function, and is also capable of interacting with multiple target cells with relevant biological effects. The rationale of Tα1 use in cancer treatment stems from the consideration that tumor progression is favored by a failure of the immune response and in turn induces immune suppression. This paper will review the historical background of Tα1 use in oncology, aiming to highlight the importance of Tα1 as an immunotherapeutic tool to be used in combination with chemotherapy, a concept that is not yet fully established in clinic.

AREAS COVERED

The efficacy and safety of combining Tα1 with chemotherapy and cytokines were first evaluated in murine tumor models, providing essential information about effects, mechanisms of action, doses and treatment protocols. The therapeutic potential of the chemo-immunotherapy protocol on metastatic melanoma and lung cancer has been confirmed in controlled clinical trials. Critical for the efficacy of the chemo-immunotherapy protocol is the dual action of Tα1 on immune effector and tumor cells.

EXPERT OPINION

On the basis of the preclinical and clinical results available, the use of the chemo-immunotherapy protocol, in which the role of Tα1 is central, is strongly recommended.

Thymosin α1 modifies podosome architecture and promptly stimulates the expression of podosomal markers in mature macrophages

BACKGROUND AND AIMS

The immunomodulatory activity of thymosin α1 (Tα1) on innate immunity has been extensively described, but its mechanism of action is not completely understood. We explored the possibility that Tα1-stimulation could affect the formation of podosomes, the highly dynamic, actin-rich, adhesion structures involved in macrophage adhesion/chemotaxis.

METHODS

The following methods were used: optical and scanning electron microscopy for analyzing morphology of human monocyte-derived macrophages (MDMs); time-lapse imaging for visualizing the time-dependent modifications induced at early times by Tα1 treatment; confocal microscopy and Western blot for analyzing localization and expression of podosome components; and Matrigel Migration Assay and zymography for testing MDM invasive ability and metalloproteinase secretion.

RESULTS

We obtained data to support that Tα1 could affect MDM motility, invasion and chemotaxis by promptly stimulating assembly and disassembly of podosomal structures. At very early times after its addition to cell culture medium and within 1 h of treatment, Tα1 induces modifications in MDM morphology and in podosomal components that are suggestive of increased podosome turnover.

CONCLUSIONS

Since impairment of podosome formation leads to reduced innate immunity and is associated with several immunodeficiency disorders, we confirm the validity of Tα1 as a potent activator of innate immunity and suggest possible new clinical application of this thymic peptide.

Historical review of thymosin α 1 in infectious diseases

INTRODUCTION

Thymosin α 1 (Tα1) is a peptidic biological response modifier, which plays a significant role in activating and regulating various cells of the immune system. For the above-mentioned activities it is expected to exert a clinical benefit in the treatment of diseases where the immune system is altered.

AREAS COVERED

Several clinical trials have been carried out with Tα1 for treatment or prevention of many different infectious diseases such as hepatitis B and C, sepsis and Aspergillosis in bone marrow-transplanted patients. Data available on the use of Tα1 in infectious disease as well as a vaccine enhancer will be reviewed to possibly generate new working hypothesis.

EXPERT OPINION

Tα1 has been widely used in thousands of patients. Nevertheless, there are some issues that have not yet been properly addressed (i.e., dose, schedule, combination treatments, end-points to be evaluated in clinical trials). In the most recent clinical trials Tα1 has been used at higher doses than those commonly used in the past showing a direct proportionality between the dose and the effect. The safety profile of Tα1 is excellent and it is virtually devoid of toxicity.

Thymosin alpha1 based immunomodulatory therapy for sepsis: a systematic review and meta-analysis

OBJECTIVES

Thymosin alpha1 (Tα1) is considered a promising immunomodulatory drug. However, it is still unclear whether Tα1 should be recommended for the management of sepsis. Here we conducted a systematic review and meta-analysis to assess the efficacy of Tα1 based immunomodulatory therapy on the clinical outcomes of septic patients.

METHODS

We searched for relevant clinical trials published before Dec. 12, 2014 through electronic databases. All articles about Tα1 based immunomodulatory therapy for sepsis were included regardless of language. Two authors independently selected studies, extracted data and assessed the quality of each included study. We polled the data related to all-cause mortality with Review Manager 5.1.

RESULTS

Twelve controlled trials were evaluated in all. Tα1 based immunomodulatory therapy had a significant trend toward lower all-cause mortality among patients with sepsis (pooled risk ratio 0.68, 95%CI 0.59-0.78, p<0.00001, 12 trials, n=1480).

CONCLUSIONS

Tα1 based immunomodulatory therapy was associated with a lower mortality in septic patients. Nevertheless, these findings should be interpreted cautiously because of the poor quality and small number of participants of the included trials. More well-designed worldwide multicenter clinical trials are needed to provide a conclusive guideline for clinical practice.

Construction, expression, and characterization of thymosin alpha 1 tandem repeats in Escherichia coli

Thymosin alpha 1 (Tα1), which is composed of 28 amino acids, has been commercialized worldwide for its immune-modulatory and antitumor effects. Tα1 can stimulate T cell proliferation and differentiation from bone marrow stem cells, augment cell-mediated immune responses, and regulate homeostasis of immune system. In this study, we developed a novel strategy to produce Tα1 concatemer (Tα1③) in Escherichia coli and compared its activity with chemically synthesized Tα1. Results showed that Tα1③ can more effectively stimulate T cell proliferation and significantly upregulate IL-2 receptor expression. We concluded that the expression system for Tα1 concatemer was constructed successfully, which could serve as an efficient tool for the production of large quantities of the active protein.

Intracellular protein degradation: from a vague idea through the lysosome and the ubiquitin-proteasome system and onto human diseases and drug targeting

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely non-lysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.

Thymosin α1 as a stimulatory agent of innate cell‐mediated immune response

The innate immune response and its cellular effectors—peripheral blood mononuclear cells and differentiated macrophages—play a crucial role in detection and elimination of pathogenic microorganisms. Chemotherapy and some immunosuppressive drugs used after organ transplantation and for treatment of autoimmune diseases have, as main side effect, bone marrow suppression, which can lead to a reduced response of the innate immune system. Hence, many immune‐depressed patients have a higher risk of developing bacterial and invasive fungal infections compared with immune‐competent individuals. Thymosin α1 (Tα1) immunomodulatory activity on effector cells of the innate immunity has been extensively described, even if its mechanism of action is not completely understood. Here, we report some of the main knowledge on this topic, focusing on our in vitro and in vivo work in progress that reinforce the validity of Tα1 as a stimulatory agent for detection and elimination of pathogens by differentiated macrophages and for restoring immune parameters after chemotherapy‐induced myelosuppression.

Synthesis and biological characterization of protease-activated prodrugs of doxazolidine

Doxazolidine (doxaz) is a new anthracycline anticancer agent. While structurally similar to doxorubicin (dox), doxaz acts via a distinct mechanism to selectively enhance anticancer activity over cardiotoxicity, the most significant clinical impediment to successful anthracycline treatment. Here, we describe the synthesis and characterization of a prodrug platform designed for doxaz release mediated by secreted proteolytic activity, a common association with invasiveness and poor prognosis in cancer patients. GaFK-Doxaz is hydrolyzable by the proteases plasmin and cathepsin B, both strongly linked with cancer progression, as well as trypsin. We demonstrate that activation of GaFK-Doxaz releases highly potent doxaz that powerfully inhibits the growth of a wide variety of cancer cells (average IC(50) of 8 nM). GaFK-Doxaz is stable in human plasma and is poorly membrane permeable, thereby limiting activation to locally secreted proteolytic activity and reducing the likelihood of severe side effects.

Molecular characterization, tissue distribution, subcellular localization and actin-sequestering function of a thymosin protein from silkworm

We identified a novel gene encoding a Bombyx mori thymosin (BmTHY) protein from a cDNA library of silkworm pupae, which has an open reading frame (ORF) of 399 bp encoding 132 amino acids. It was found by bioinformatics that BmTHY gene consisted of three exons and two introns and BmTHY was highly homologous to thymosin betas (Tβ). BmTHY has a conserved motif LKHTET with only one amino acid difference from LKKTET, which is involved in Tβ binding to actin. A His-tagged BmTHY fusion protein (rBmTHY) with a molecular weight of approximately 18.4 kDa was expressed and purified to homogeneity. The purified fusion protein was used to produce anti-rBmTHY polyclonal antibodies in a New Zealand rabbit. Subcellular localization revealed that BmTHY can be found in both Bm5 cell (a silkworm ovary cell line) nucleus and cytoplasm but is primarily located in the nucleus. Western blotting and real-time RT-PCR showed that during silkworm developmental stages, BmTHY expression levels are highest in moth, followed by instar larvae, and are lowest in pupa and egg. BmTHY mRNA was universally distributed in most of fifth-instar larvae tissues (except testis). However, BmTHY was expressed in the head, ovary and epidermis during the larvae stage. BmTHY formed complexes with actin monomer, inhibited actin polymerization and cross-linked to actin. All the results indicated BmTHY might be an actin-sequestering protein and participate in silkworm development.

Intracellular protein degradation: from a vague idea thru the lysosome and the ubiquitin-proteasome system and onto human diseases and drug targeting

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code was transcribed to RNA and translated to proteins, but how proteins were degraded had remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis was largely non-lysosomal, but the mechanisms involved have remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Thymosin alpha 1: past clinical experience and future promise

Thymosin alpha 1, originally isolated as the compound responsible for reconstitution of immune function in thymectomized animal models, has enjoyed a wide-ranging clinical development program over the past decades, extending across multiple companies, indications, countries, and continents. This paper provides an overview of this complex picture. The extensive clinical studies began with small studies conducted with an impure mixture of peptides under the aegis of physician-sponsored INDs submitted to the US FDA, in subjects with primary immune deficiency such as DiGeorge syndrome. Subsequent studies ranged all the way to large phase-3 trials conducted with synthetically produced thymosin alpha 1 and hundreds of patients, in many countries including the United States, Italy, and China.

Optimized Fmoc solid-phase synthesis of Thymosin alpha1 by side-chain anchoring onto a PEG resin

Thymosin alpha1 is a 28-amino acid acetylated peptide used for the treatment of hepatitis B and C. This peptide has a difficult sequence because of the presence of consecutive beta-branched amino acids and shows a tendency to form beta-sheet structures, partly as a result of the many protecting groups required to assemble the peptide (up to 20 side-chain protecting groups). Consequently, its synthesis has been generally achieved by convergent solution chemistry. Here we report a straightforward stepwise solid-phase synthesis on a polyethylene glycol solid-support that enables the scaling-up of this key therapeutic peptide.

Solid-phase Synthesis of a Peptide Derivative of Thymosin alpha1 and Initial Studies on its99mTc-Radiolabelling

A derivative (1) of the immunopotentiating 28-peptide thymosin alpha1 has been especially designed, so that it can be (99m)Tc-radiolabelled, and synthesized following the Fmoc solid-phase peptide synthesis approach. Derivative 1 contains the N-terminal fragment Talpha1[1-14] as a bioactive segment, at the C-terminus of which a (99m)Tc-chelating moiety consisting of N(alpha),N(alpha)-dimethylglycine, serine and cysteine is linked through the N(epsilon)-amino group of a 'bifunctional' lysine residue; the latter is indirectly anchored on the solid-phase peptide synthesis resin through 6-aminocaproic acid (dmGSCK{N(epsilon)-Talpha1[1-14]}Aca). Synthetic derivative 1 was obtained at high overall yield (approximately 35%) and purity (>95%) and shown to be efficiently radiolabelled with (99m)Tc, thus resulting in the first, to our knowledge, so far reported (99m)Tc-radiolabelled derivative of thymosin alpha1, which may be eventually used as a specific molecular tool for the in vitro/in vivo study of the mode of action of the parent bioactive peptide.

History of the discovery of the thymosins

From a historical perspective, the studies that led to the isolation and characterization of the thymosins began in earnest in the early 1960s in the laboratory of Abraham White at the Albert Einstein College of Medicine in New York. In a 1966 paper in the Proceedings of the National Academy of Sciences, U.S., we first named these thymic-derived factors "Thymosins." By 1972, the thymosin team had moved to the University of Texas Medical Branch in Galveston (UTMB) where an extremely talented group of young scientists and students succeeded over the next 6 years in preparing and testing a highly active partially purified calf thymus preparation, termed thymosin fraction-5 (TF5), which was amenable for scale-up and suitable for clinical use. In 1974, we received the first IND for a thymic hormone preparation from the FDA to begin a phase-I study with TF5 in children with primary immunodeficiency diseases at the University of California Medical Center in San Francisco. The immunorestorative and potentially life-saving properties of TF5 in clinical medicine were first documented in a landmark paper in 1975 by Drs. Arthur Ammann and Diane Wara in the New England Journal of Medicine. TF5 consists of a family of at least 40 mostly small acidic polypeptides, with molecular weights ranging from 1000 to 15,000 Da. This article will identify the key scientists and the milestones involved in the initial studies with TF5 that have led to the chemical characterization of the thymosins and to translational studies from the lab bench to the clinic.

Intracellular protein degradation: from a vague idea thru the lysosome and the ubiquitin-proteasome system and onto human diseases and drug targeting

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely non-lysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitinproteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.

Intracellular protein degradation: from a vague idea thru the lysosome and the ubiquitin-proteasome system and onto human diseases and drug targeting

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely non-lysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.

Intracellular protein degradation: from a vague idea thru the lysosome and the ubiquitin-proteasome system and onto human diseases and drug targeting

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve, it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely nonlysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.

Intracellular Protein Degradation: From a Vague Idea, through the Lysosome and the Ubiquitin-Proteasome System, and onto Human Diseases and Drug Targeting (Nobel Lecture)

Between the 1950s and 1980s, scientists were focusing mostly on how the genetic code is transcribed to RNA and translated to proteins, but how proteins are degraded has remained a neglected research area. With the discovery of the lysosome by Christian de Duve it was assumed that cellular proteins are degraded within this organelle. Yet, several independent lines of experimental evidence strongly suggested that intracellular proteolysis is largely non-lysosomal, but the mechanisms involved remained obscure. The discovery of the ubiquitin-proteasome system resolved the enigma. We now recognize that degradation of intracellular proteins is involved in regulation of a broad array of cellular processes, such as the cell cycle and division, regulation of transcription factors, and assurance of the cellular quality control. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of human disease, such as malignancies and neurodegenerative disorders, which led subsequently to an increasing effort to develop mechanism-based drugs.

Proteolysis: from the lysosome to ubiquitin and the proteasome

How the genetic code is translated into proteins was a key focus of biological research before the 1980s, but how these proteins are degraded remained a neglected area. With the discovery of the lysosome, it was suggested that cellular proteins are degraded in this organelle. However, several independent lines of experimental evidence strongly indicated that non-lysosomal pathways have an important role in intracellular proteolysis, although their identity and mechanisms of action remained obscure. The discovery of the ubiquitin-proteasome system resolved this enigma.

The thymosins. Prothymosin alpha, parathymosin, and beta-thymosins: structure and function

The studies on thymosins were initiated in 1965, when the group of A. White searched for thymic factors responsible for the physiological functions of thymus. To restore thymic functions in thymic-deprived or immunodeprived animals, as well as in humans with primary immuno-deficiency diseases and in immunosuppressed patients, a standardized extract from bovine thymus gland called thymosin fraction 5 was prepared. Thymosin fraction 5 indeed improved immune response. It turned out that thymosin fraction 5 consists of a mixture of small polypeptides. Later on, several of these peptides (polypeptide beta 1, thymosin alpha 1, prothymosin alpha, parathymosin, and thymosin beta 4) were isolated and tested for their biological activity. The research of many groups has indicated that none of the isolated peptides is really a thymic hormone; nevertheless, they are biologically important peptides with diverse intracellular and extracellular functions. Studies on these functions are still in progress. The current status of knowledge of structure and functions of the thymosins is discussed in this review.

Prothymosin alpha promotes cell proliferation in NIH3T3 cells

Thymic hormones have immunomodulatory effects on T cells and hence have been used clinically to restore the immunity of immunodeficient patients as well as to enhance the cellular immunity of cancer patients. Prothymosin alpha, which is a member of the thymic hormone family, has recently been suggested to act as a nuclear protein participating in the stimulation of cell proliferation. To characterize the biological activities ofprothymosin alpha in vitro, we established NIH3T3 cell transformants that constitutively express higher prothymosin alpha protein and its mRNA compared with the wild-type counterpart. Cells that overexpressed prothymosin alpha increased the proliferative activity assayed by the [3H]-thymidine incorporation or by the cell cycle analysis with the fluorescent-activated cell sorter. The results provide direct evidence that prothymosin alpha plays a role in cell proliferation by shortening the duration of the G1 phase.