AM-879, a PPARy non-agonist and Ser273 phosphorylation blocker, promotes insulin sensitivity without adverse effects in mice

Obesity is one of the main risk factors for type 2 diabetes, and peroxisome proliferator-activated receptor γ (PPARγ) is considered a promising pathway on insulin sensitivity and adipose tissue metabolism. The search for molecules acting as insulin sensitizers have increased, especially for molecules that block PPARγ-Ser273 phosphorylation, without reaching full agonism. We evaluated the in vivo effects of AM-879, a PPARγ non-agonist, and found that AM-879 exerts different effects in mice depending on the dose. At lower doses, this ligand decreased BAT, increased leptin and Crh expression. However, at a higher dose, it promoted improvement on insulin sensitivity, ameliorates expression of metabolism-related genes, decreased the expression of genes related to liver toxicity, maintaining body weight and adipocyte size. These results present a new lead molecule to ameliorates insulin resistance and confirm AM-879 as a PPARγ non-agonist which blocks Ser273 phosphorylation as a good strategy to modulate insulin sensitivity without developing the adverse effects promoted by PPARγ full agonists.

Impaired expression of serine/arginine protein kinase 2 (SRPK2) affects melanoma progression

Melanoma is one of the most aggressive tumors, and its lethality is associated with the ability of malignant cells to migrate and invade surrounding tissues to colonize distant organs and to generate widespread metastasis. The serine/arginine protein kinases 1 and 2 (SRPK1 and SRPK2) are classically related to the control of pre-mRNA splicing through SR protein phosphorylation and have been found overexpressed in many types of cancer, including melanoma. Previously, we have demonstrated that the pharmacological inhibition of SRPKs impairs pulmonary colonization of metastatic melanoma in mice. As the used compounds could target at least both SRPK1 and SRPK2, here we sought to obtain additional clues regarding the involvement of these paralogs in melanoma progression. We analyzed single-cell RNA sequencing data of melanoma patient cohorts and found that SRPK2 expression in melanoma cells is associated with poor prognosis. Consistently, CRISPR-Cas9 genome targeting of SRPK2, but not SRPK1, impaired actin polymerization dynamics as well as the proliferative and invasive capacity of B16F10 cells in vitro. In further in vivo experiments, genetic targeting of SRPK2, but not SRPK1, reduced tumor progression in both subcutaneous and caudal vein melanoma induction models. Taken together, these findings suggest different functional roles for SRPK1/2 in metastatic melanoma and highlight the relevance of pursuing selective pharmacological inhibitors of SRPK2.

Intracellular hyaluronic acid-binding protein 4 (HABP4): a candidate tumor suppressor in colorectal cancer

Hyaluronic Acid-binding protein 4 (HABP4) is a regulatory protein of 57 kDa that is functionally involved in transcription regulation and RNA metabolism and shows several characteristics common to oncoproteins or tumor suppressors, including altered expression in cancer tissues, nucleus/cytoplasm shuttling, intrinsic lack of protein structure, complex interactomes and post translational modifications. Its gene has been found in a region on chromosome 9q22.3-31, which contains SNP haplotypes occurring in individuals with a high risk for familial colon cancer. To test a possible role of HABP4 in tumorigenesis we generated knockout mice by the CRISPR/Cas9 method and treated the animals with azoxymethane (AOM)/dextran sodium sulfate (DSS) for induction of colon tumors. HABP4-/- mice, compared to wild type mice, had more and larger tumors, and expressed more of the proliferation marker proteins Cyclin-D1, CDK4 and PCNA. Furthermore, the cells of the bottom of the colon crypts in the HABP4-/- mice divided more rapidly. Next, we generated also HABP4-/- HCT 116 cells, in cell culture and found again an increased proliferation in clonogenic assays in comparison to wild-type cells. Our study of the protein expression levels of HABP4 in human colon cancer samples, through immunohistochemistry assays, showed, that 30% of the tumors analyzed had low expression of HABP4. Our data suggest that HABP4 is involved in proliferation regulation of colon cells in vitro and in vivo and that it is a promising new candidate for a tumor suppressor protein that can be explored both in the diagnosis and possibly therapy of colon cancer.

Complex interactomes and post-translational modifications of the regulatory proteins HABP4 and SERBP1 suggest pleiotropic cellular functions

The 57 kDa antigen recognized by the Ki-1 antibody, is also known as intracellular hyaluronic acid binding protein 4 and shares 40.7% identity and 67.4% similarity with serpin mRNA binding protein 1, which is also named CGI-55, or plasminogen activator inhibitor type-1-RNA binding protein-1, indicating that they might be paralog proteins, possibly with similar or redundant functions in human cells. Through the identification of their protein interactomes, both regulatory proteins have been functionally implicated in transcriptional regulation, mRNA metabolism, specifically RNA splicing, the regulation of mRNA stability, especially, in the context of the progesterone hormone response, and the DNA damage response. Both proteins also show a complex pattern of post-translational modifications, involving Ser/Thr phosphorylation, mainly through protein kinase C, arginine methylation and SUMOylation, suggesting that their functions and locations are highly regulated. Furthermore, they show a highly dynamic cellular localization pattern with localizations in both the cytoplasm and nucleus as well as punctuated localizations in both granular cytoplasmic protein bodies, upon stress, and nuclear splicing speckles. Several reports in the literature show altered expressions of both regulatory proteins in a series of cancers as well as mutations in their genes that may contribute to tumorigenesis. This review highlights important aspects of the structure, interactome, post-translational modifications, sub-cellular localization and function of both regulatory proteins and further discusses their possible functions and their potential as tumor markers in different cancer settings.

Opposing action of NCoR1 and PGC-1α in mitochondrial redox homeostasis

The ability to respond to fluctuations of reactive oxygen species (ROS) within the cell is a central aspect of mammalian physiology. This dynamic process depends on the coordinated action of transcriptional factors to promote the expression of genes encoding for antioxidant enzymes. Here, we demonstrate that the transcriptional coregulators, PGC-1α and NCoR1, are essential mediators of mitochondrial redox homeostasis in skeletal muscle cells. Our findings reveal an antagonistic role of these coregulators in modulating mitochondrial antioxidant induction through Sod2 transcriptional control. Importantly, the activation of this mechanism by either PGC-1α overexpression or NCoR1 knockdown attenuates mitochondrial ROS levels and prevents cell death caused by lipid overload in skeletal muscle cells. The opposing actions of coactivators and corepressors, therefore, exert a commanding role over cellular antioxidant capacity.

Human Regulatory Protein Ki-1/57 Is a Target of SUMOylation and Affects PML Nuclear Body Formation

Ki-1/57 is a nuclear and cytoplasmic regulatory protein first identified in malignant cells from Hodgkin's lymphoma. It is involved in gene expression regulation on both transcriptional and mRNA metabolism levels. Ki-1/57 belongs to the family of intrinsically unstructured proteins and undergoes phosphorylation by PKC and methylation by PRMT1. Previous characterization of its protein interaction profile by yeast two-hybrid screening showed that Ki-1/57 interacts with proteins of the SUMOylation machinery, the SUMO E2 conjugating enzyme UBC9 and the SUMO E3 ligase PIAS3, which suggested that Ki-1/57 could be involved with this process. Here we identified seven potential SUMO target sites (lysine residues) on Ki-1/57 sequence and observed that Ki-1/57 is modified by SUMO proteins in vitro and in vivo. We showed that SUMOylation of Ki-1/57 occurred on lysines 213, 276, and 336. In transfected cells expressing FLAG-Ki-1/57 wild-type, its paralog FLAG-CGI-55 wild-type, or their non-SUMOylated triple mutants, the number of PML-nuclear bodies (PML-NBs) is reduced compared with the control cells not expressing the constructs. More interestingly, after treating cells with arsenic trioxide (As₂O₃), the number of PML-NBs is no longer reduced when the non-SUMOylated triple mutant Ki-1/57 is expressed, suggesting that the SUMOylation of Ki-1/57 has a role in the control of As₂O₃-induced PML-NB formation. A proteome-wide analysis of Ki-1/57 partners in the presence of either SUMO-1 or SUMO-2 suggests that the involvement of Ki-1/57 with the regulation of gene expression is independent of the presence of either SUMO-1 or SUMO-2; however, the presence of SUMO-1 strongly influences the interaction of Ki-1/57 with proteins associated with cellular metabolism, maintenance, and cell cycle.

Defeating Bacterial Resistance and Preventing Mammalian Cells Toxicity Through Rational Design of Antibiotic-Functionalized Nanoparticles

The rational synthesis of alternative materials is highly demanding due to the outbreak of infectious diseases and resistance to antibiotics. Herein, we report a tailored nanoantibiotic synthesis protocol where the antibiotic binding was optimized on the silver-silica core-shell nanoparticles surface to maximize biological responses. The obtained silver nanoparticles coated with mesoporous silica functionalized with ampicillin presented remarkable antimicrobial effects against susceptible and antibiotic-resistant Escherichia coli. In addition, these structures were not cell-death inducers and different steps of the mitotic cell cycle (prophase, anaphase and metaphase) were clearly identified. The superior biological results were attributed to a proper and tailored synthesis strategy.

Hydrocephalus and arthrogryposis in an immunocompetent mouse model of ZIKA teratogeny: A developmental study

The teratogenic mechanisms triggered by ZIKV are still obscure due to the lack of a suitable animal model. Here we present a mouse model of developmental disruption induced by ZIKV hematogenic infection. The model utilizes immunocompetent animals from wild-type FVB/NJ and C57BL/6J strains, providing a better analogy to the human condition than approaches involving immunodeficient, genetically modified animals, or direct ZIKV injection into the brain. When injected via the jugular vein into the blood of pregnant females harboring conceptuses from early gastrulation to organogenesis stages, akin to the human second and fifth week of pregnancy, ZIKV infects maternal tissues, placentas and embryos/fetuses. Early exposure to ZIKV at developmental day 5 (second week in humans) produced complex manifestations of anterior and posterior dysraphia and hydrocephalus, as well as severe malformations and delayed development in 10.5 days post-coitum (dpc) embryos. Exposure to the virus at 7.5-9.5 dpc induces intra-amniotic hemorrhage, widespread edema, and vascular rarefaction, often prominent in the cephalic region. At these stages, most affected embryos/fetuses displayed gross malformations and/or intrauterine growth restriction (IUGR), rather than isolated microcephaly. Disrupted conceptuses failed to achieve normal developmental landmarks and died in utero. Importantly, this is the only model so far to display dysraphia and hydrocephalus, the harbinger of microcephaly in humans, as well as arthrogryposis, a set of abnormal joint postures observed in the human setting. Late exposure to ZIKV at 12.5 dpc failed to produce noticeable malformations. We have thus characterized a developmental window of opportunity for ZIKV-induced teratogenesis encompassing early gastrulation, neurulation and early organogenesis stages. This should not, however, be interpreted as evidence for any safe developmental windows for ZIKV exposure. Late developmental abnormalities correlated with damage to the placenta, particularly to the labyrinthine layer, suggesting that circulatory changes are integral to the altered phenotypes.

Tailored silica-antibiotic nanoparticles: overcoming bacterial resistance with low cytotoxicity

New and more aggressive antibiotic resistant bacteria arise at an alarming rate and represent an ever-growing challenge to global health care systems. Consequently, the development of new antimicrobial agents is required to overcome the inefficiency of conventional antibiotics and bypass treatment limitations related to these pathologies. In this study, we present a synthesis protocol, which was able to entrap tetracycline antibiotic into silica nanospheres. Bactericidal efficacy of these structures was tested against bacteria that were susceptible and resistant to antibiotics. For nonresistant bacteria, our composite had bactericidal efficiency comparable to that of free-tetracycline. On the other hand, the synthesized composites were able to avoid bacterial growth of resistant bacteria while free-tetracycline has shown no significant bactericidal effect. Finally, we have investigated the cytotoxicity of these nanoparticles against mammalian cells to check any possible poisoning effect. It was found that these nanospheres are not apoptosis-inducers and only a reduction on the cell replication rate was seen when compared to the control without nanoparticles.