Steroid receptor coactivators – their role in immunity

Steroid Receptor Coactivators (SRCs) are essential regulators of transcription with a wide range of impact on human physiology and pathology. In immunology, SRCs play multiple roles; they are involved in the regulation of nuclear factor-κB (NF-κB), macrophage (MΦ) activity, lymphoid cells proliferation, development and function, to name just a few. The three SRC family members, SRC-1, SRC-2 and SRC-3, can exert their immunological function either in an independent manner or act in synergy with each other. In certain biological contexts, one SRC family member can compensate for lack of activity of another member, while in other cases one SRC can exert a biological function that competes against the function of another family counterpart. In this review we illustrate the diverse biological functionality of the SRCs with regard to their role in immunity. In the light of recent development of SRC small molecule inhibitors and stimulators, we discuss their potential relevance as modulators of the immunological activity of the SRCs for therapeutic purposes

Vegetative Change on South Padre Island, Texas, over Twenty Years and Evaluation of Multispectral Videography in Determining Vegetative Cover and Species Identity

A comparative vegetation analysis of an island-wide transect of South Padre Island, Texas, was conducted in 1997 using aerial multispectral digital videography and line intercept ground truth techniques to assess the usefulness of videography in estimating vegetative cover and species identifications. Ground truth data were used to assess vegetative change occurring in the 20 years since the report of Judd et al. (1977) on the vegetation of South Padre Island. Estimates of total cover by ground truth and remote sensing techniques were similar (2.45% difference) on South Padre Island. Thus, airborne multispectral digital videography is an effective technique for assessing changes in total vegetative cover of Texas barrier islands. This technique will be an effective tool for documenting changes in total cover on barrier islands due to natural perturbations such as hurricanes and human disturbances including vehicular traffic. Imagery obtained at altitudes of 200 m or greater did not permit discrimination of dominant species in each of an island\u27s topographic zones. However, acquisition of imagery at a time of the year when dominant species are in specific phenological stages, such as flowering, and at a lower altitude may facilitate their recognition. Comparison of data from a single trans-island transect in 1997 with data from three trans-island transects and 18 transects across the foreshore, backshore, and primary dunes in 1977 suggests that there has been a marked decrease in species richness of the backshore and primary dune zones of South Padre Island. There also was a change in dominant species in the backshore zone. These changes in species richness and dominance may be largely attributable to vehicular traffic in these zones. - Un análisis comparativo de la vegetación de un transecto transinsular de la isla South Padre en el estado de Texas fue realizado en 1997 usando videografía aérea multiesprectral digital y técnicas de validación de intercepción linear terrestre para evaluar la utilidad de la videografía en la estimación de la cobertura vegetal e identificación de especies. Los datos de estudios de validación terrestre fueron utilizados para evaluar el cambio vegetativo que ocurrió durante 20 años después del informe de Judd et al (1977) sobre la vegetación de la isla South Padre. Las estimaciones de la cobertura total mediante técnicas de validación terrestres y de medición remota fueron similares (2.45% de diferencia) en la isla South Padre. Por lo tanto, la videografía multiesprectral digital aérea se considera una técnica eficaz para evaluar cambios en la cobertura vegetal de las islas barrera de Texas. Esta técnica será una herramienta efectiva para documentar los cambios de cobertura total en las islas barrera debido a las perturbaciones naturales tales como huracanes y disturbios humanos como tráfico vehicular. Las imágenes obtenidas en altitudes de 200 metros o mayores no permitieron la discriminación de las especies dominantes de las varias zonas topográficas de una isla. Sin embargo, la adquisición de imágenes de una época del año en que las especies dominantes están en etapas fenológicas específicas, tales como la floración, y desde una altitud menor, puede facilitar su reconocimiento. Al comparar datos de un transecto transinsular de 1977 con los de tres transectos transinsulares y de 18 transectos correspondientes a la parte frontal, trasera, y de las dunas primarias de la isla en 1977, se sugiere que ha habido una marcada disminución en la riqueza de especies en la parte trasera y en la zona de dunas primarias de la isla South Padre. También hubo un cambio de especies dominantes en la zona trasera. Estos cambios en la riqueza y dominancia de especies pueden ser atribuidos en gran parte al tráfico vehicular en estas zonas

Tamoxifen Inhibits ER-negative Breast Cancer Cell Invasion and Metastasis by Accelerating Twist1 Degradation

Twist1 is a transcription factor driving epithelial-mesenchymal transition, invasion and metastasis of breast cancer cells. Mice with germ-line Twist1 knockout are embryonic lethal, while adult mice with inducible Twist1 knockout have no obvious health problems, suggesting that Twist1 is a viable therapeutic target for the inhibition of invasion and metastasis of breast cancer in adult patients. In this study, we expressed a luciferase protein or a Twist1-luciferase fusion protein in HeLa cells as part of a high throughput system to screen 1280 compounds in the Library of Pharmacologically Active Compounds (LOPAC) from Sigma-Aldrich for their effects on Twist1 protein expression. One of the most interesting compounds identified is tamoxifen, a selective estrogen receptor (ER) modulator used to treat ER-positive breast cancer. Tamoxifen treatment significantly accelerated Twist1 degradation in multiple cell lines including HEK293 human kidney cells, 4T1 and 168FARN mouse mammary tumor cells with either ectopically or endogenously expressed Twist1. Tamoxifen-induced Twist1 degradation could be blocked by the MG132 proteasome inhibitor, suggesting that tamoxifen induces Twist1 degradation through the ubiquitination-proteasome pathway. However, tamoxifen-induced Twist1 degradation was independent of Twist1 mRNA expression, estrogen signaling and MAPK-mediated Twist1 phosphorylation in these cells. Importantly, tamoxifen also significantly inhibited invasive behavior in Matrigel and lung metastasis in SCID-bg mice of ER-negative 4T1 mammary tumor cells, which depend on endogenous Twist1 to invade and metastasize. These results indicate that tamoxifen can significantly accelerate Twist1 degradation to suppress cancer cell invasion and metastasis, suggesting that tamoxifen can be used not only to treat ER-positive breast cancers but also to reduce Twist1-mediated invasion and metastasis in ER-negative breast cancers

miRNA Regulatory Circuits in ES Cells Differentiation: A Chemical Kinetics Modeling Approach

MicroRNAs (miRNAs) play an important role in gene regulation for Embryonic Stem cells (ES cells), where they either down-regulate target mRNA genes by degradation or repress protein expression of these mRNA genes by inhibiting translation. Well known tables TargetScan and miRanda may predict quite long lists of potential miRNAs inhibitors for each mRNA gene, and one of our goals was to strongly narrow down the list of mRNA targets potentially repressed by a known large list of 400 miRNAs. Our paper focuses on algorithmic analysis of ES cells microarray data to reliably detect repressive interactions between miRNAs and mRNAs. We model, by chemical kinetics equations, the interaction architectures implementing the two basic silencing processes of miRNAs, namely “direct degradation” or “translation inhibition” of targeted mRNAs. For each pair (M,G) of potentially interacting miRMA gene M and mRNA gene G, we parameterize our associated kinetic equations by optimizing their fit with microarray data. When this fit is high enough, we validate the pair (M,G) as a highly probable repressive interaction. This approach leads to the computation of a highly selective and drastically reduced list of repressive pairs (M,G) involved in ES cells differentiation

Specific ubiquitin-conjugating enzymes promote degradation of specific nuclear receptor coactivators

Nuclear receptor coactivators (NRCoAs) are nuclear hormone receptor-associated regulatory proteins that interact with members of the nuclear receptor superfamily in the presence of their cognate ligand, enhancing their transcriptional activity. The identification of ubiquitin-proteasome pathway proteins as coactivators provides evidence that ubiquitin-proteasome-mediated protein degradation plays an integral role in eukaryotic gene transcription. It has also been observed that nuclear receptors themselves are ubiquitinated and degraded in a hormone-dependent manner and that ubiquitin-proteasome function is essential for most nuclear receptors to function as transactivators. Here, we show that specific ubiquitin-proteasome pathway enzymes target specific NRCoA proteins in vivo and in vitro. First, using a temperature-sensitive cell line that contains a thermolabile ubiquitin-activating E1 enzyme, we confirmed that NRCoA proteins are targets of the ubiquitin-proteasome pathway. Then using coimmunoprecipitation studies, we also demonstrate that in vivo, NRCoA proteins are ubiquitinated. Finally, we illustrate that in vitro, NRCoA ubiquitination and degradation depend on the ubiquitin-activating enzyme (E1) and on specific ubiquitin-conjugating enzymes (E2) for each of the coactivators

Drug Combination in Cancer Treatment—From Cocktails to Conjugated Combinations

It is well recognized today that anticancer drugs often are most effective when used in combination. However, the establishment of chemotherapy as key modality in clinical oncology began with sporadic discoveries of chemicals that showed antiproliferative properties and which as a first attempt were used as single agents. In this review we describe the development of chemotherapy from its origins as a single drug treatment with cytotoxic agents to polydrug therapy that includes targeted drugs. We discuss the limitations of the first chemotherapeutic drugs as a motivation for the establishment of combined drug treatment as standard practice in spite of concerns about frequent severe, dose limiting toxicities. Next, we introduce the development of targeted treatment as a concept for advancement within the broader field of small-molecule drug combination therapy in cancer and its accelerating progress that was boosted by recent scientific and technological progresses. Finally, we describe an alternative strategy of drug combinations using drug-conjugates for selective delivery of cytotoxic drugs to tumor cells that potentiates future improvement of drug combinations in cancer treatment. Overall, in this review we outline the development of chemotherapy from a pharmacological perspective, from its early stages to modern concepts of using targeted therapies for combinational treatment

Inhibition of the 26S proteasome blocks progesterone receptor-dependent transcription through failed recruitment of RNA polymerase II

In the present study, we investigated the involvement of protein degradation via the 26S proteasome during progesterone receptor (PR)-mediated transcription in T-47D cells containing a stably integrated MMTV–CAT reporter construct (CAT0 cells). Progesterone induced CAT and HSD11β2 transcription while co-treatment with the proteasome inhibitor, MG132, blocked PR-induced transcription in a time-dependent fashion. MG132 treatment also inhibited transcription of β-actin and cyclophilin, but not two proteasome subunit genes, PSMA1 and PSMC1, indicating that proteasome inhibition affects a subset of RNA polymerase II (RNAP II)-regulated genes. Progesterone-mediated recruitment of RNAP II was blocked by MG132 treatment at time points later than 1 h that was not dependent on the continued presence of PR, associated cofactors, and components of the general transcription machinery, supporting the concept that proteasome-mediated degradation is needed for continued transcription. Surprisingly, progesterone-mediated acetylation of histone H4 was inhibited by MG132 with the concomitant recruitment of HDAC3, NCoR, and SMRT. We demonstrate that the steady-state protein levels of SMRT and NCoR are higher in the presence of MG132 in CAT0 cells, consistent with other reports that SMRT and NCoR are targets of the 26S proteasome. However, inhibition of histone deacetylation by trichostatin A (TSA) treatment or SMRT/NCoR knockdown by siRNA did not restore MG132-inhibited progesterone-dependent transcription. Therefore, events other than histone deacetylation and stability of SMRT and NCoR must also play a role in inhibition of PR-mediated transcription

The 26S Proteasome Is Required for Estrogen Receptor-α and Coactivator Turnover and for Efficient Estrogen Receptor-α Transactivation

Estrogen receptor-α (ERα) is downregulated in the presence of its cognate ligand, estradiol (E2), through the ubiquitin proteasome pathway. Here, we show that ubiquitin proteasome function is required for ERα to serve as a transcriptional activator. Deletion of the last 61 amino acids of ERα, including residues that form helix 12, abolishes ligand-mediated downregulation of the receptor as do point mutations in the ligand binding domain that impair coactivator binding. In addition, coactivators also are subject to degradation by the 26S proteasome, but their intrinsic transcriptional activity is not affected. These data provide evidence that protein interactions with ERα coactivator binding surfaces are important for ligand-mediated receptor downregulation and suggest that receptor and coactivator turnover contributes to ERα transcriptional activity