Expression and purification of functional epitope of pigment epithelium-derived factor in E. coli with inhibiting effect on endothelial cells

A Phagosomally Expressed Gene, rv0428c, of Mycobacterium tuberculosis Demonstrates Acetyl Transferase Activity and Plays a Protective Role Under Stress Conditions

Mycobacterium tuberculosis genome is composed of several hypothetical gene products that need to be characterized for understanding the physiology of bacteria. Rv0428c was one of the 11 proteins exclusively identified within the phagosomal compartment of macrophages infected with mycobacteria and marked as hypothetical. The expression of rv0428c gene was upregulated under acidic and nutritive stress conditions in M. tuberculosis H37Ra, which was supported by potential sigma factor binding sites in the region upstream to the rv0428c gene. The bioinformatics analysis predicted it to be a GCN5- acetyl transferase, belonging to the Histone acetyl transferase (HAT) family. The docking analysis predicted formation of hydrogen bonds and hydrophobic interactions between donor acetyl-co-A and histone H3 tail region. rv0428c gene was cloned and expressed in E. coli. The protein was purified to homogeneity and was fairly stable over a wide range of pH 5.0–9.0 and temperature up to 40 °C. The HAT activity of purified Rv0428c was confirmed by in vitro acetylation assay using recombinant H3 histone expressed in bacteria as substrate, which increased in time dependent manner. The results suggested that it is the second confirmed acetyl transferase in M. tuberculosis H37Rv. Furthermore, rv0428c was over expressed in surrogate host M. smegmatis, which led to enhanced growth rate and altered colony morphology. The expression of rv0428c in M. smegmatis promoted the survival of bacteria under acidic and nutritive stress conditions. In conclusion, Rv0428c, a phagosomal acetyl transferase of M. tuberculosis, might be involved in survival under stress conditions.

The Expression Levels and Cellular Localization of Pigment Epithelium Derived Factor (PEDF) in Mouse Testis: Its Possible Involvement in the Differentiation of Spermatogonial Cells

Pigment epithelium derived factor (PEDF) is a multifunctional secretory soluble glycoprotein that belongs to the serine protease inhibitor (serpin) family. It was reported to have neurotrophic, anti-angiogenic and anti-tumorigenic activity. Recently, PEDF was found in testicular peritubular cells and it was assumed to be involved in the avascular nature of seminiferous tubules. The aim of this study was to determine the cellular origin, expression levels and target cells of PEDF in testicular tissue of immature and adult mice under physiological conditions, and to explore its possible role in the process of spermatogenesis in vitro. Using immunofluorescence staining, we showed that PEDF was localized in spermatogenic cells at different stages of development as well as in the somatic cells of the testis. Its protein levels in testicular homogenates and Sertoli cells supernatant showed a significant decrease with age. PEDF receptor (PEDF-R) was localized within the seminiferous tubule cells and in the interstitial cells compartment. Its RNA expression levels showed an increase with age until 8 weeks followed by a decrease. RNA levels of PEDF-R showed the opposite trend of the protein. Addition of PEDF to cultures of isolated cells from the seminiferous tubules did not changed their proliferation rate, however, a significant increase was observed in number of meiotic/post meiotic cells at 1000 ng/mL of PEDF; indicating an in vitro differentiation effect. This study may suggest a role for PEDF in the process of spermatogenesis.

PEDF and its roles in physiological and pathological conditions: implication in diabetic and hypoxia-induced angiogenic diseases

Pigment epithelium-derived factor (PEDF) is a broadly expressed multifunctional member of the serine proteinase inhibitor (serpin) family. This widely studied protein plays critical roles in many physiological and pathophysiological processes, including neuroprotection, angiogenesis, fibrogenesis and inflammation. The present review summarizes the temporal and spatial distribution patterns of PEDF in a variety of developing and adult organs, and discusses its functions in maintaining physiological homoeostasis. The major focus of the present review is to discuss the implication of PEDF in diabetic and hypoxia-induced angiogenesis, and the pathways mediating PEDF's effects under these conditions. Furthermore, the regulatory mechanisms of PEDF expression, function and degradation are also reviewed. Finally, the therapeutic potential of PEDF as an anti-angiogenic drug is briefly summarized.

Proapoptotic PEDF functional peptides inhibit prostate tumor growth--a mechanistic study

PEDF inhibits tumor growth via anti-angiogenic activity; however, the direct effect of PEDF on prostate carcinoma and its functional epitope as well as the underlying mechanism regulating the pathway from extracellular receptors to nuclear transcription factors has not been fully elucidated. This study investigates the ability and mechanism by which the functional PEDF peptides PEDF34 and PEDF44 suppress tumor growth. The results showed that death receptor pathway was activated by PEDF34 through up-regulation of FasL and activation of caspase-8 in both xenograft tumor tissues and PC-3 cells. FasL knockdown by siRNA or JNK-p inhibition attenuated apoptosis induced by PEDF34. NF-κB and PPARγ are crucial transcription factors for FasL expression. PEDF34 up-regulated PPARγ but did not affect NF-κB. PEDF34-induced up-regulation of FasL was abolished by siRNA-mediated PPARγ knockdown or using PPARγ inhibitor GW9662, whereas inhibition of NF-κB by the inhibitor PDTC or by siRNA had no effect. Furthermore, activation of JNK is necessary for PEDF34-induced up-regulation of FasL. PEDF34 has stronger hydropathicity and more interactions with laminin receptor than PEDF44. Blocking the laminin receptor abolished the up-regulation of FasL and PPARγ by PEDF34. Moreover, PEDF34 uses a similar mechanism to induce apoptosis in both endothelial and cancer cells. This study provides evidence that PEDF34, not PEDF44, serves as the proapoptotic epitope and exerts proapoptotic activity in both cancer and endothelial cells through activation of the extrinsic death receptor pathway. The dual anti-tumor and anti-angiogenic activities of PEDF34 suggest that it may be a promising agent for the treatment of prostate cancer.

The effects of PEDF on cancer biology: mechanisms of action and therapeutic potential

The potent actions of pigment epithelium-derived factor (PEDF) on tumour-associated cells, and its extracellular localization and secretion, stimulated research on this multifunctional serpin. Such studies have identified several PEDF receptors and downstream signalling pathways. Known cellular PEDF responses have expanded from the initial discovery that PEDF induces retinoblastoma cell differentiation to its anti-angiogenic, antitumorigenic and antimetastatic properties. Although the diversity of PEDF activities seems to be complex, they are consistent with the varied mechanisms that regulate this multimodal factor. If PEDF is to be used for cancer management, a deeper appreciation of its many functions and mechanisms of action is needed.

[Recombinant fragment of pigment epithelium-derived factor (44-77) prevents pathological corneal neovascularization]

Pigment epithelium-derived factor (PEDF), a 50 kDa secreted glycoprotein, is among the most potent endogenous inhibitors of angiogenesis. PEDF-derived fragment (44-77) possesses antiangiogenic properties of the full-sized protein and is a potential drug candidate for the treatment of ocular neovascular diseases. In this study we propose an efficient scalable biotechnological method for the production of PEDF (44-77) as part of a fusion protein with SspDnaB intein. The fusion protein was obtained in bacterial E. coli cells in the form of inclusion bodies, solubilized and subjected to autocatalytic cleavage with the release of PEDF (44-77) (yield, 77%). The target peptide was separated from the intein using tangential ultrafiltration. The final purification of PEDF (44-77) was performed by reversed-phase HPLC. The yield of the target peptide (purity, 99%) was 65 mg per 1 liter of culture. Antiangiogenic activity of the obtained peptide was studied in vitro using murine endothelial cells SVEC-4-10. PEDF (44-77) suppressed proliferation of endothelial cells by 53% and inhibited endothelial cell tube formation at the concentration of 1 nM. The ability of the recombinant PEDF (44-77) to block initial stages of angiogenesis was demonstrated using the model of rabbit corneal neovascularization.

The emerging role of PEDF in stem cell biology

Encoded by a single gene, PEDF is a 50 kDa glycoprotein that is highly conserved and is widely expressed among many tissues. Most secreted PEDF deposits within the extracellular matrix, with cell-type-specific functions. While traditionally PEDF is known as a strong antiangiogenic factor, more recently, as this paper highlights, PEDF has been linked with stem cell biology, and there is now accumulating evidence demonstrating the effects of PEDF in a variety of stem cells, mainly in supporting stem cell survival and maintaining multipotency.

Anti-angiogenic peptides for cancer therapeutics

Peptides have emerged as important therapeutics that are being rigorously tested in angiogenesis-dependent diseases due to their low toxicity and high specificity. Since the discovery of endogenous proteins and protein fragments that inhibit microvessel formation (thrombospondin, endostatin) several peptides have shown promise in pre-clinical and clinical studies for cancer. Peptides have been derived from thrombospondin, collagens, chemokines, coagulation cascade proteins, growth factors, and other classes of proteins and target different receptors. Here we survey recent developments for anti-angiogenic peptides with length not exceeding 50 amino acid residues that have shown activity in pre-clinical models of cancer or have been tested in clinical trials; some of the peptides have been modified and optimized, e.g., through L-to-D and non-natural amino acid substitutions. We highlight technological advances in peptide discovery and optimization including computational and bioinformatics tools and novel experimental techniques.