Influence of prothymosin-alpha on HIV-1 target cells

Identification of Diagnostic Markers Correlated With HIV+ Immune Non-response Based on Bioinformatics Analysis

Background: HIV-infected immunological non-responders (INRs) are characterized by their inability to reconstitute CD4⁺ T cell pools after antiretroviral therapy. The risk of non-AIDS-related diseases in INRs is increased, and the outcome and prognosis of INRs are inferior to that of immunological responders (IRs). However, few markers can be used to define INRs precisely. In this study, we aim to identify further potential diagnostic markers associated with INRs through bioinformatic analyses of public datasets.

Methods: This study retrieved the microarray data sets of GSE106792 and GSE77939 from the Gene Expression Omnibus (GEO) database. After merging two microarray data and adjusting the batch effect, differentially expressed genes (DEGs) were identified. Gene Ontology (GO) resource and Kyoto Encyclopedia of Genes and Genomes (KEGG) resource were conducted to analyze the biological process and functional enrichment. We performed receiver operating characteristic (ROC) curves to filtrate potential diagnostic markers for INRs. Gene Set Enrichment Analysis (GSEA) was conducted to perform the pathway enrichment analysis of individual genes. Single sample GSEA (ssGSEA) was performed to assess scores of immune cells within INRs and IRs. The correlations between the diagnostic markers and differential immune cells were examined by conducting Spearman’s rank correlation analysis. Subsequently, miRNA-mRNA-TF interaction networks in accordance with the potential diagnostic markers were built with Cytoscape. We finally verified the mRNA expression of the diagnostic markers in clinical samples of INRs and IRs by performing RT-qPCR.

Results: We identified 52 DEGs in the samples of peripheral blood mononuclear cells (PBMC) between INRs and IRs. A few inflammatory and immune-related pathways, including chronic inflammatory response, T cell receptor signaling pathway, were enriched. FAM120AOS, LTA, FAM179B, JUN, PTMA, and SH3YL1 were considered as potential diagnostic markers. ssGSEA results showed that the IRs had significantly higher enrichment scores of seven immune cells compared with IRs. The miRNA-mRNA-TF network was constructed with 97 miRNAs, 6 diagnostic markers, and 26 TFs, which implied a possible regulatory relationship.

Conclusion: The six potential crucial genes, FAM120AOS, LTA, FAM179B, JUN, PTMA, and SH3YL1, may be associated with clinical diagnosis in INRs. Our study provided new insights into diagnostic and therapeutic targets.

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Prothymosin-α enhances phosphatase and tensin homolog expression and binds with tripartite motif-containing protein 21 to regulate Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 signaling in human bladder cancer

Prothymosin‐α (PTMA) is a small, acidic protein that is usually transported into the nucleus and involves many cellular and immunological functions. Previous studies demonstrated that aberrant location of PTMA expression exists in human bladder cancer, but the role of PTMA protein expression remains elusive. In this study, we created ectopic nuclear or cytoplasmic PTMA expression in human bladder cancer cells by infecting lentiviruses carrying wild type or deleted nuclear localization signal of the PTMA gene. The in vivo tumorigenesis assay showed PTMA protein with deleted nuclear localization signal promotes J82 xenograft tumor growth in mice and shortens their survival more so than the wild type. Chromatin immunoprecipitation showed that wild‐type PTMA protein binds to the PTEN promoter and enhances phosphatase and tensin homolog (PTEN) expression. Through immunoblot proteomics and in vivo ubiquitination studies, PTMA protein can bind with tripartite motif‐containing protein 21 (TRIM21) and block its ubiquitination. Also, TRIM21 can downregulate both forms of PTMA protein. In human bladder tumors, loss of nuclear PTMA expression was an unfavorable prognostic indicator for shorter disease‐free survival (hazard ratio, 1.54; P = 0.009). Our data support that nuclear PTMA protein serves as a tumor suppressor in bladder cancer through upregulating PTEN and orchestrating TRIM21 for the regulation of Nrf2 signaling.

Ecto-F0/F1 ATPase as a novel candidate of prothymosin α receptor

OBJECTIVES

Prothymosin α (ProTα) was reported to inhibit the neuronal necrosis by facilitating the plasma membrane localization of endocytosed glucose transporter 1/4 through an activation of putative G_i-coupled receptor. The present study aims to identify a novel ProTα target, which may lead to an activation of G_i-coupled receptor.

METHODS

We used G_i-rich lipid rafts fraction of retinal cell line N18-RE-105 cells for affinity cross-linking. The biological confirmation that F₀/F₁ ATPase is a target protein complex was performed by cell-free experiments using ELISA-based binding assay, surface plasmon resonance assay and quartz crystal microbalance assay, and cell-based experiments to measure extracellular ATP level in the HUVECs culture.

RESULTS

From the cross-linking study and above-mentioned protein-protein interaction assays, ATP5A1 and ATP5B, F₁ ATPase subunits were found to ProTα binding target proteins. In the culture of HUVEC cells, furthermore, ProTα increased the extracellular ATP levels in a reversible manner by anti-ATP5A1- and ATP5B-antibodies.

CONCLUSION

The present study suggests that ProTα may activate ecto-F₀/F₁ ATPase and produced ATP. This study leads to next subjects whether produced ATP and its metabolites, ADP or adenosine may activate corresponding G_i-coupled receptors.

In vivo biodistribution and imaging studies with a 99mTc-radiolabeled derivative of the C-terminus of prothymosin alpha in mice bearing experimentally-induced inflammation

Prothymosin alpha (ProTα) is a highly conserved mammalian polypeptide (109 amino acids in man) exerting in vitro and in vivo immunoenhancing activities. Recently, our team has developed a ^99mTc-radiolabeled derivative of the C-terminal bioactive decapeptide of ProTα ([^99mTc]C1) and employed it in in vitro studies, the results of which support the existence of binding sites on human neutrophils that recognize [^99mTc]C1, intact ProTα as well as the C-terminal decapeptide of ProTα and presumably involve Toll-like receptor 4. In the present work, [^99mTc]C1 was administered to Swiss albino mice with experimentally-induced inflammation for in vivo biodistribution and imaging studies, in parallel with a suitable negative control, which differs from [^99mTc]C1 only in bearing a scrambled version of the ProTα decapeptide. The biodistribution data obtained with [^99mTc]C1 demonstrated fast clearance of radioactivity from blood, heart, lungs, normal muscle, and predominantly urinary excretion. Most importantly, slow clearance of radioactivity from the inflammation focus was observed, resulting in a high ratio of inflamed/normal muscle tissue (9.15 at 30min post injection, which remained practically stable up to 2h). The inflammation-targeting capacity of [^99mTc]C1 was confirmed by imaging studies and might be attributed to neutrophils, which are recruited at the inflamed areas and bear binding sites for [^99mTc]C1. In this respect, apart from being a valuable tool for further studies on ProTα in in vitro and in vivo systems, [^99mTc]C1 merits further evaluation as a radiopharmaceutical for specific imaging of inflammation foci.

Subcellular dissemination of prothymosin alpha at normal physiology: immunohistochemical vis-a-vis western blotting perspective

BACKGROUND

The cell type, cell status and specific localization of Prothymosin α (PTMA) within cells seemingly determine its function. PTMA undergoes 2 types of protease proteolytic modifications that are useful in elucidating its interactions with other molecules; a factor that typifies its roles. Preferably a nuclear protein, PTMA has been shown to function in the cytoplasm and extracellularly with much evidence leaning on pathognomonic status. As such, determination of its cellular distribution under normal physiological context while utilizing varied techniques is key to illuminating prospective validation of its distinct functions in different tissues. Differential distribution insights at normal physiology would also portent better basis for further clarification of its interactions and proteolytic modifications under pathological conditions like numerous cancer, ischemic stroke and immunomodulation. We therefore raised an antibody against the C terminal of PTMA to use in tandem with available antibody against the N terminal in a murine model to explicate the differences in its distribution in brain cell types and major peripheral organs through western blotting and immunohistochemical approaches.

RESULTS

The newly generated antibody was applied against the N-terminal antibody to distinguish truncated versions of PTMA or deduce possible masking of the protein by other interacting molecules. Western blot analysis indicated presence of a truncated form of the protein only in the thymus, while immunohistochemical analysis showed that in brain hippocampus the full-length PTMA was stained prominently in the nucleus whereas in the stomach full-length PTMA staining was not observed in the nucleus but in the cytoplasm.

CONCLUSION

Truncated PTMA could not be detected by western blotting when both antibodies were applied in all tissues examined except the thymus. However, immunohistochemistry revealed differential staining by these antibodies suggesting possible masking of epitopes by interacting molecules. The differential localization patterns observed in the context of nucleic versus cytoplasmic presence as well as punctate versus diffuse pattern in tissues and cell types, warrant further investigations as to the forms of PTMA interacting partners.

Heroin inhibits HIV-restriction miRNAs and enhances HIV infection of macrophages

Although opioids have been extensively studied for their impact on the immune system, limited information is available about the specific actions of opioids on intracellular antiviral innate immunity against HIV infection. Thus, we investigated whether heroin, one of the most abused drugs, inhibits the expression of intracellular HIV restriction microRNA (miRNA) and facilitates HIV replication in macrophages. Heroin treatment of macrophages enhanced HIV replication, which was associated with the downregulation of several HIV restriction miRNAs. These heroin-mediated actions on the miRNAs and HIV could be antagonized by naltrexone, an opioid receptor antagonist. Furthermore, the in vitro negative impact of heroin on HIV-associated miRNAs was confirmed by the in vivo observation that heroin addicts had significantly lower levels of macrophage-derived HIV restriction miRNAs than those in the control subjects. These in vitro and in vivo findings indicate that heroin use compromises intracellular anti-HIV innate immunity, providing a favorable microenvironment for HIV survival in the target cells.

Tongue sole (Cynoglossus semilaevis) prothymosin alpha: Cytokine-like activities associated with the intact protein and the C-terminal region that lead to antiviral immunity via Myd88-dependent and -independent pathways respectively

Prothymosin alpha (ProTα) is a small protein that in mammals is known to participate in diverse biological processes including immunomodulation. In teleost, the immunological function of ProTα is unknown. In the current study, we investigated the expression and function of the ProTα (named CsProTα) from the teleost fish tongue sole (Cynoglossus semilaevis). We found that CsProTα expression was abundant in immune relevant tissues and upregulated by megalocytivirus infection. Immunoblot detected secretion of CsProTα by peripheral blood leukocytes. Recombinant CsProTα (rCsProTα) as well as the C-terminal 11-residue (Ct11) were able to bind head kidney monocytes (HKM) and induce immune gene expression; however, the induction patterns caused by rCsProTα and Ct11 differed considerably. When introduced in vivo, rCsProTα and Ct11 significantly reduced megalocytivirus infection in fish tissues, whereas rCsProTα antibody significantly promoted viral replication. Blocking of Myd88 activity abolished the virus-inhibitory effect of rCsProTα but not Ct11. Taken together, these results demonstrate for the first time that both the intact protein and the C-terminal segment of a teleost ProTα can act like cytokines and induce antiviral immunity via, however, distinct signaling pathways that differ in the requirement of Myd88.

Prothymosin alpha expression and localization during the spermatogenesis ofDanio rerio

Prothymosin α (PTMA) is a highly acidic, intrinsically disordered protein, which is widely expressed and conserved throughout evolution; its uncommon features are reflected by its involvement in a variety of processes, including chromatin remodelling, transcriptional regulation, cell proliferation and death, immunity. PTMA has also been implicated in spermatogenesis: during vertebrate germ cell progression in the testis the protein is expressed in meiotic and post-meiotic stages, and it is associated with the acrosome system of the differentiating spermatids in mammals. Then, it finally localizes on the inner acrosomal membrane of the mature spermatozoa, suggesting its possible role in both the maturation and function of the gametes. In the present work we studied PTMA expression during the spermatogenesis of the adult zebrafish, a species in which two paralogs have been described. Our data show thatptmatranscripts are expressed in the testis, and localize in meiotic and post-meiotic germ cells, namely spermatocytes and spermatids. Consistently, the protein is expressed in spermatocytes, spermatids, and spermatozoa: its initial perinuclear distribution is extended to the chromatin region during cell division and, in haploid phases, to the cytoplasm of the developing and final gametes. The nuclear localization in the acrosome-lacking spermatozoa suggests a role for PTMA in chromatin remodelling during gamete differentiation. These data further provide a compelling starting point for the study of PTMA functions during vertebrate fertilization.

Prothymosin α variants isolated from CD8+ T cells and cervicovaginal fluid suppress HIV-1 replication through type I interferon induction

Soluble factors from CD8(+) T cells and cervicovaginal mucosa of women are recognized as important in controlling human immunodeficiency virus type 1 (HIV-1) infection and transmission. Previously, we have shown the strong anti-HIV-1 activity of prothymosin α (ProTα) derived from CD8(+) T cells. ProTα is a small acidic protein with wide cell distribution, to which several functions have been ascribed, depending on its intracellular or extracellular localization. To date, activities of ProTα have been attributed to a single protein known as isoform 2. Here we report the isolation and identification of 2 new ProTα variants from CD8(+) T cells and cervicovaginal lavage with potent anti-HIV-1 activity. The first is a splice variant of the ProTα gene, known as isoform CRA_b, and the second is the product of a ProTα gene, thus far classified as a pseudogene 7. Native or recombinant ProTα variants potently restrict HIV-1 replication in macrophages through the induction of type I interferon. The baseline expression of interferon-responsive genes in primary human cervical tissues positively correlate with high levels of intracellular ProTα, and the knockdown of ProTα variants by small interfering RNA leads to downregulation of interferon target genes. Overall, these findings suggest that ProTα variants are innate immune mediators involved in immune surveillance.

Specific in vitro binding of a new (99m)Tc-radiolabeled derivative of the C-terminal decapeptide of prothymosin alpha on human neutrophils

Prothymosin alpha (ProTα) is a conserved mammalian polypeptide with intracellular functions associated with cell proliferation and apoptosis and an extracellular role associated with immunopotentiation. The N-terminal fragment [1-28], which is identical with the immunostimulating peptide thymosin α1 (Tα1), was earlier considered as the immunoactive region of the polypeptide; however, recent data suggest that ProTα may exert a discrete immunomodulating action through its central or C-terminal region, via targeting Toll-like receptor- 4 (TLR4). In this work, a derivative of the C-terminal fragment ProTα[100-109] (ProTα-D1) that can be radiolabeled with (99m)Tc was developed. The biological activity of the non-radioactive (185/187)rhenium-complex of this derivative ([(185/187)Re]ProTα-D1, structurally similar with [(99m)Tc]ProTα-D1) was verified through suitable in vitro bioassays on human neutrophils. Subsequent cell-binding studies revealed specific, time-dependent and saturable binding of [(99m)Tc]ProTα-D1 on neutrophils, which was inhibited by intact ProTα and ProTα[100-109], as well as by a "prototype" TLR4-ligand (lipopolysaccharide from Escherichia coli). Overall, our results support the existence of ProTα-binding sites on human neutrophils, recognizing [(99m)Tc]ProTα-D1, which might involve TLR4. [(99m)Tc]ProTα-D1 may be a useful tool for conducting further in vitro and in vivo studies, aiming to elucidate the extracellular mode of action of ProTα and, eventually, develop ProTα-based immunotherapeutics.

Intracellular and extracellular cytokine-like functions of prothymosin α: implications for the development of immunotherapies

Prothymosin α (ProTα) is a 12.5-kDa, highly acidic protein widely distributed in different cell types expressed intracellularly and extracellularly. ProTα does not contain a secretion-signal sequence and is released by a nonclassical secretory pathway with a cargo protein. New findings on the extracellular function of ProTα have yielded exciting insights into the cytokine-like functions of this host protein that stimulates type I interferon via Toll-like receptor 4. Here, we discuss the intracellular function of ProTα, how new findings of cytokine-like activities of ProTα aid our understanding of mechanisms that direct ProTα functions, and the potential application of these new insights to the development of immunotherapies.

Prothymosin-alpha inhibits HIV-1 via Toll-like receptor 4-mediated type I interferon induction

Induction of type I interferons (IFN) is a central feature of innate immune responses to microbial pathogens and is mediated via Toll-like receptor (TLR)-dependent and -independent pathways. Prothymosin-alpha (ProTalpha), a small acidic protein produced and released by CD8(+) T cells, inhibits HIV-1, although the mechanism for its antiviral activity was not known. We demonstrate that exogenous ProTalpha acts as a ligand for TLR4 and stimulates type I IFN production to potently suppress HIV-1 after entry into cells. These activities are induced by native and recombinant ProTalpha, retained by an acidic peptide derived from ProTalpha, and lost in the absence of TLR4. Furthermore, we demonstrate that ProTalpha accounts for some of the soluble postintegration HIV-1 inhibitory activity long ascribed to CD8(+) cells. Thus, a protein produced by CD8(+) T cells of the adaptive immune system can exert potent viral suppressive activity through an innate immune response. Understanding the mechanism of IFN induction by ProTalpha may provide therapeutic leads for IFN-sensitive viruses.

Lambda interferon inhibits human immunodeficiency virus type 1 infection of macrophages

The newly identified type III interferon (IFN-lambda) has antiviral activity against a broad spectrum of viruses. We thus examined whether IFN-lambda has the ability to inhibit human immunodeficiency virus type 1 (HIV-1) infection of blood monocyte-derived macrophages that expressed IFN-lambda receptors. Both IFN-lambda1 and IFN-lambda2, when added to macrophage cultures, inhibited HIV-1 infection and replication. This IFN-lambda-mediated anti-HIV-1 activity is broad, as IFN-lambda could inhibit infection by both laboratory-adapted and clinical strains of HIV-1. Investigations of the mechanism(s) responsible for the IFN-lambda action showed that although IFN-lambda had little effect on HIV-1 entry coreceptor CCR5 expression, IFN-lambda induced the expression of CC chemokines, the ligands for CCR5. In addition, IFN-lambda upregulated intracellular expression of type I IFNs and APOBEC3G/3F, the newly identified anti-HIV-1 cellular factors. These data provide direct and compelling evidence that IFN-lambda, through both extracellular and intracellular antiviral mechanisms, inhibits HIV-1 replication in macrophages. These findings indicate that IFN-lambda may have therapeutic value in the treatment of HIV-1 infection.