Comparative Analysis of Human, Mouse, and Pig Glial Fibrillary Acidic Protein Gene Structures

HIV Nef Expression Down-modulated GFAP Expression and Altered Glutamate Uptake and Release and Proliferation in Astrocytes

HIV infection of astrocytes leads to restricted gene expression and replication but abundant expression of HIV early genes Tat, Nef and Rev. A great deal of neuroHIV research has so far been focused on Tat protein, its effects on astrocytes, and its roles in neuroHIV. In the current study, we aimed to determine effects of Nef expression on astrocytes and their function. Using transfection or infection of VSVG-pseudotyped HIV viruses, we showed that Nef expression down-modulated glial fibrillary acidic protein (GFAP) expression. We then showed that Nef expression also led to decreased GFAP mRNA expression. The transcriptional regulation was further confirmed using a GFAP promoter-driven reporter gene assay. We performed transcription factor profiling array to compare the expression of transcription factors between Nef-intact and Nef-deficient HIV-infected cells and identified eight transcription factors with expression changes of 1.5-fold or higher: three up-regulated by Nef (Stat1, Stat5, and TFIID), and five down-regulated by Nef (AR, GAS/ISRE, HIF, Sp1, and p53). We then demonstrated that removal of the Sp1 binding sites from the GFAP promoter resulted in a much lower level of the promoter activity and reversal of Nef effects on the GFAP promoter, confirming important roles of Sp1 in the GFAP promoter activity and for Nef-induced GFAP expression. Lastly, we showed that Nef expression led to increased glutamate uptake and decreased glutamate release by astrocytes and increased astrocyte proliferation. Taken together, these results indicate that Nef leads to down-modulation of GFAP expression and alteration of glutamate metabolism in astrocytes, and astrocyte proliferation and could be an important contributor to neuroHIV.

Importance of the pig as a human biomedical model

[Figure: see text].

Astrocyte Senescence and Alzheimer's Disease: A Review

Astrocytes are the largest group of glial cells in the brain and participate in several essential functions of the central nervous system (CNS). Disruption of their normal physiological function can lead to metabolism disequilibrium and the pathology of CNS. As an important mechanism of aging, cellular senescence has been considered as a primary inducing factor of age-associated neurodegenerative disorders. Senescent astrocytes showed decreased normal physiological function and increased secretion of senescence-associated secretory phenotype (SASP) factors, which contribute to Aβ accumulation, tau hyperphosphorylation, and the deposition of neurofibrillary tangles (NFTs) in Alzheimer’s disease (AD). Astrocyte senescence also leads to a number of detrimental effects, including induced glutamate excitotoxicity, impaired synaptic plasticity, neural stem cell loss, and blood–brain barrier (BBB) dysfunction. In this review article, we have summarized the growing findings regarding astrocyte senescence and its putative role in the pathologic progress of AD. Additionally, we also focus on the significance of targeting astrocyte senescence as a novel and feasible therapeutic approach for AD.

Dysregulated epidermal growth factor and tumor growth factor-beta receptor signaling through GFAP-ACTA2 protein interaction in liver fibrosis

OBJECTIVE

Viral hepatitis is associated with high morbidity and mortality. Identification of biological pathways involved in hepatic fibrosis resulting from chronic hepatitis C are essential for better management of patients. Constructing the HCV-human protein interaction network through bioinformatics may enable us to discover diagnostic biological pathways. We investigated to identify dysregulated pathways and gene enrichment based on actin alpha 2 (ACTA2) and glial fibrillar acidic protein (GFAP) interaction network analysis in hepatic fibrosis.

METHODS

This is an in-silico study conducted at Ziauddin University from March,2019 to September 2019. Enrichment and protein-protein interaction (PPI) network analysis of the identified proteins: GFAP and ACTA2 along with their mapped gene data sets was performed using FunRich version 3.1.3.

RESULTS

Biological pathway grouping showed enrichment of proteins (85.7%) in signalling pathway by epidermal growth factor receptor (EGFR) and Tumor growth factor (TGF)-beta Receptor followed by signaling by PDGF, FGFR and NGF (71.4%) (p < 0.001). SRC, PRKACA, PRKCA and PRKCD were enriched in both EGFR and TGF-beta Signalling pathways.

CONCLUSION

EGFR and TGF-beta signalling pathways were enriched in liver fibrosis. SRC, PRKACA, PRKCA and PRKCD were enriched and differentially expressed in both EGFR and TGF-beta signalling pathways.

Production of transgenic pigs using a pGFAP-CreERT2/EGFP LoxP inducible system for central nervous system disease models

Transgenic (TG) pigs are important in biomedical research and are used in disease modeling, pharmaceutical toxicity testing, and regenerative medicine. In this study, we constructed two vector systems by using the promoter of the pig glial fibrillary acidic protein (pGFAP) gene, which is an astrocyte cell marker. We established donor TG fibroblasts with pGFAP-CreER^T2/LCMV-EGFP^LoxP and evaluated the effect of the transgenes on TG-somatic cell nuclear transfer (SCNT) embryo development. Cleavage rates were not significantly different between control and transgene-donor groups. Embryo transfer was performed thrice just before ovulation of the surrogate sows. One sow delivered 5 TG piglets at 115 days after pregnancy. Polymerase chain reaction (PCR) analysis with genomic DNA isolated from skin tissues of TG pigs revealed that all 5 TG pigs had the transgenes. EGFP expression in all organs tested was confirmed by immunofluorescence staining and PCR. Real-time PCR analysis showed that pGFAP promoter-driven Cre fused to the mutated human ligand-binding domain of the estrogen receptor (CreER^T2) mRNA was highly expressed in the cerebrum. Semi-nested PCR analysis revealed that CreER^T2-mediated recombination was induced in cerebrum and cerebellum but not in skin. Thus, we successfully generated a TG pig with a 4-hydroxytamoxifen (TM)-inducible pGFAP-CreER^T2/EGFP^LoxP recombination system via SCNT.

Selection of similar single domain antibodies from two immune VHH libraries obtained from two alpacas by using different selection methods

The two most used methods to select camelid single-domain antibody-fragments (VHHs) are: displaying their repertoires on the surface of filamentous bacteriophages (phage display) or linking them to ribosomes (ribosome display). In this study, we compared specific VHHs isolated from two different immune libraries coming from two different alpacas by using these two selection methods. Three anti-GFAP (glial fibrillary acidic protein) VHHs were derived from an immune library obtained by ribosome display after immunization of one alpaca with purified GFAP, a protein expressed by astroglial cells. In parallel, three other anti-GFAP VHHs were derived from an immune library by phage display after immunization of another alpaca with a human brain tissue extract containing GFAP. All the VHHs were closely related and one VHH was found to be strictly identical in both studies. This highlights the selection pressure exerted by the camelid immune system to shape the paratope of an antibody against a defined antigen.