Reduction of thymosin beta4 and actin in HL60 cells during apoptosis is preceded by a decrease of their mRNAs

In vivo growth suppression of CT-26 mouse colorectal cancer cells by adenovirus-expressed small hairpin RNA specifically targeting thymosin beta-4 mRNA

Thymosin beta-4 (Tβ4) is known to be involved in tumorigenesis. Overexpression of this polypeptide has been observed in a wide variety of cancers, including colorectal carcinoma (CRC). Accordingly, Tβ4 has been proposed to be a novel therapeutic target for CRC, especially in its metastatic form. Although in vitro tumor-suppressive effects of Tβ4 gene silencing mediated by small hairpin RNA (shRNA) have already been demonstrated, the in vivo efficacy of such an approach has not yet been reported. Herein, we demonstrated that infection with recombinant adenovirus expressing an shRNA targeting Tβ4 markedly reduced the growth of and robustly induced apoptosis in CT-26 mouse CRC cells in culture. Additionally, tumors grown in nude mice from the CT-26 cells whose Tβ4 expression already been downregulated by virus infection were also drastically reduced. Most importantly, significant growth arrest of tumors derived from the parental CT-26 cells was observed after multiple intratumoral injections of these viruses. Together, our results show for the first time that in vivo silencing of Tβ4 expression by its shRNA generated after adenoviral infection can suppress CRC growth. These results further demonstrate the feasibility of treating CRC by a Tβ4 knockdown gene therapeutic approach.

UPLC-ESI-MS analysis of thymosins β4 and β10 in cell lysates: a simple, rapid and sensitive quantification method

Fast and reproducible quantification of thymosins β4 and β10 in different cell cultures was achieved by ultra high performance liquid chromatography coupled to mass spectrometry. We demonstrated that cancer cell lines all exhibit a higher amount of Tβ10 compared to control cells, whereas the level of Tβ4 is drastically depending on cell lines.

Thymosin beta4 and its posttranslational modifications

Thymosin beta(4) as well as the other members of the beta-thymosin family are important G-actin sequestering peptides. The chemical properties, the biosynthesis, and posttranslational modifications (PTMs) of these peptides are discussed. During biosynthesis of thymosin beta(4) the initiator methionine is removed and the N-terminus is acetylated. Research on proteomics revealed several acetylated lysine residues and two phosphorylated threonine residues. The enormous number of phosphorylable and acetylable sites in the human proteome raises the question about the biological significance of these PTMs in the context of beta-thymosins. Presently, this question cannot be answered because neither the concentration of these modified beta-thymosins in cells is known nor the consequences of the modifications on the biological function(s) of beta-thymosins have been studied yet. Thymosin beta(4) is also posttranslationally modified by transglutaminase forming covalent bonds with other molecules. Prolyl oligopeptidase generates ac-SDKP from thymosin beta(4). The concentration of C-terminal peptide fragments of thymosin beta(4) is elevated in the blood of patients with rheumatoid arthritis.

The mouse thymosin beta15 gene family displays unique complexity and encodes a functional thymosin repeat

We showed earlier that human beta-thymosin 15 (Tb15) is up-regulated in prostate cancer, confirming studies from others that propagated Tb15 as a prostate cancer biomarker. In this first report on mouse Tb15, we show that, unlike in humans, four Tb15-like isoforms are present in mouse. We used phylogenetic analysis of deuterostome beta-thymosins to show that these four new isoforms cluster within the vertebrate Tb15-clade. Intriguingly, one of these mouse beta-thymosins, Tb15r, consists of two beta-thymosin domains. The existence of such a repeat beta-thymosin is so far unique in vertebrates, though common in lower eukaryotes. Biochemical data indicate that Tb15r potently sequesters actin. In a cellular context, Tb15r behaves as a bona fide beta-thymosin, lowering central stress fibre content. We reveal that a complex genomic organization underlies Tb15r expression: Tb15r results from read-through transcription and alternative splicing of two tandem duplicated mouse Tb15 genes. Transcript profiling of all mouse beta-thymosin isoforms (Tb15s, Tb4 and Tb10) reveals that two isoform switches occur between embryonic and adult tissues, and indicates Tb15r as the major mouse Tb15 isoform in adult cells. Tb15r is present also in mouse prostate cancer cell lines. This insight into the mouse Tb15 family is fundamental for future studies on Tb15 in mouse (prostate) cancer models.

Degradation of transglutaminase 2 by calcium-mediated ubiquitination responding to high oxidative stress

Transglutaminase 2 (TG2) is a calcium-dependent enzyme that catalyzes the transamidation reaction. There is conflicting evidence on the role of TG2 in apoptosis. In this report, we show that TG2 increases in response to low level of oxidative stress, whereas TG2 diminishes under high stress conditions. Monitoring TG2 expression, activity and calcium concentration in cells treated with A23187 revealed that the initial rise of calcium activates TG2 but subsequent calcium-overload induces the degradation of TG2 via calcium-mediated polyubiquitination. These results indicate that the role of TG2 in apoptosis depends on the level of calcium influx triggered by oxidative stress.

Comparative analysis of the acute response of the trout, O. mykiss, head kidney to in vivo challenge with virulent and attenuated infectious hematopoietic necrosis virus and LPS-induced inflammation

BACKGROUND

The response of the trout, O. mykiss, head kidney to bacterial lipopolysaccharide (LPS) or active and attenuated infectious hematopoietic necrosis virus (IHNV and attINHV respectively) intraperitoneal challenge, 24 and 72 hours post-injection, was investigated using a salmonid-specific cDNA microarray.

RESULTS

The head kidney response to i.p. LPS-induced inflammation in the first instance displays an initial stress reaction involving suppression of major cellular processes, including immune function, followed by a proliferative hematopoietic-type/biogenesis response 3 days after administration. The viral response at the early stage of infection highlights a suppression of hematopoietic and protein biosynthetic function and a stimulation of immune response. In fish infected with IHNV a loss of cellular function including signal transduction, cell cycle and transcriptional activity 72 hours after infection reflects the tissue-specific pathology of IHNV infection. attIHNV treatment on the other hand shows a similar pattern to native IHNV infection at 24 hours however at 72 hours a divergence from the viral response is seen and replace with a recovery response more similar to that observed for LPS is observed.

CONCLUSION

In conclusion we have been able to identify and characterise by transcriptomic analysis two different types of responses to two distinct immune agents, a virus, IHNV and a bacterial cell wall component, LPS and a 'mixed' response to an attenuated IHNV. This type of analysis will lead to a greater understanding of the physiological response and the development of effective immune responses in salmonid fish to different pathogenic and pro-inflammatory agents.

Identification and characterization of homologues of vertebrate beta-thymosin in the marine mollusk Aplysia californica

The beta-thymosins have been known as actin-sequestering proteins, but now are recognized as molecules with multiple and diverse intracellular and extracellular functions. Two closely related proteins, beta-thymosin(His) and beta-thymosin(Gln), have been de novo sequenced by top-down mass spectrometry in the common neurobiology model, Aplysia californica. As determined by nanoelectrospray quadrupole-enhanced Fourier-Transform mass spectrometry with collisionally activated and electron-capture dissociations, both of these Aplysia beta-thymosins are acetylated and differ by a single residue in the central actin-binding domain. Profiling of individual cells and tissue by matrix-assisted laser desorption/ionization mass spectrometry reveals that these proteins are widely expressed in the Aplysia central nervous system, including in individual identified neurons, neuronal clusters, nerves and connective tissues. Newly identified beta-thymosin(His) and beta-thymosin(Gln) are also detected by mass spectrometry in hemolymph, and in releasates collected from whole ganglia. When applied exogenously, beta-thymosin proteins, purified from nerve cell extract, support the anchoring of neurons, and increase neurite sprouting and total neurite outgrowth in culture. These positive effects on neurite regeneration in cell culture suggest that the beta-thymosin proteins have an extracellular function in the central nervous system of Aplysia californica.

Presence of a peptide component of thymosin fraction-5 manifesting discrete cytostatic properties in HL-60 human promyelocytic leukemia cells

Thymosin fraction-5 (TF5), an array of small molecular weight peptides present in crude extracts of the adult bovine thymus, contains numerous constituents with demonstrable biological activity. Because TF5 generally enhances immune reactivity in a variety of settings, and additionally restricts proliferation of certain neoplasms, we examined the effects of TF5 on proliferative capacity in the human promyelocytic leukemia cell line HL-60. Vital dye-exclusion, oxidative metabolism of chromogenic dyes, and clonogenic growth profiles were monitored to assess rates of cellular proliferation; our results demonstrate that TF5 restricted HL-60 cell growth, an influence that exhibited comparable potency and efficacy among all three indices. This antiproliferative activity was labile, insofar as medium conditioned in HL-60 cells for 24 h became devoid of the initial growth-suppressive activity after 24-h culture when subsequently administered to naive cultures. Review of cytoarchitectural traits, chromatin staining by TUNEL, and fluorescent cytometric analyses demonstrated that TF5 failed to elicit apoptosis, however, suggesting that this material instead drove treated cells into growth arrest and an unanticipated cytostasis. Qualitatively similar responses were noted in the human monoblastic leukemia cell line U937. Partial purification of TF5 by FPLC yielded a component containing an antiproliferative activity associated with the approximately 1000-Da fraction. These results demonstrate that TF5 contains a sub-fraction possessing a growth-suppressive activity capable of restraining normal proliferation of human myeloid neoplasms via the apparent induction of true cytostasis.

Possible functional involvement of thymosin beta 4 in developing tooth germ of mouse lower first molar

We examined the detailed in situ expression pattern of thymosin beta 4 (Tbeta4) in the developing mouse mandibular first molar. Tbeta4 mRNA was expressed in the presumptive dental epithelium at embryonic day 10.5 (E10.5) and in the thickened dental epithelium at E12. An in situ signal was observed in the invaginated epithelial bud at E13, in the enamel organ at E14 and E14.5, and in the primary enamel knot (PEK) at E14.5. The signal was localized in the epithelial cells of the outer layer of the enamel organ at E15 and E15.5. No signal was found in the PEK at these stages. Tbeta4 mRNA was expressed in the inner enamel epithelium, cervical loop and dental lamina at E16 and E17. The expression of Tbeta4 mRNA was observed in the polarized inner epithelial cells at E18, newborn day 1 (N1) and N2. However, the signal intensity decreased markedly at N3. We herein report for the first time that Tbeta4 is distinctly expressed in developing tooth germ, and it may also play functional roles in the initiation, growth and differentiation of tooth germ.