Cysteine mediated disulfide bond formation in RAGE V domain facilitates its functionally relevant dimerization

A regulation mechanism for the promoter region of the pet II operon in Acidithiobacillus ferrooxidans ATCC23270

Acidithiobacillus ferrooxidans ATCC23270 is a gram-negative and autotrophic bacillus acquiring energy via the oxidation of iron and sulfur. The pet II operon is involved in the sulfur metabolism of A. ferrooxidans. However, the mechanisms that control the expression of the pet II operon are poorly understood. We previously described that the AFE2726 protein is associated with the expression of the pet II operon. Here, we attempted to analyze the involvement of AFE2726 in the regulation of pet II operon expression. First, pEGF recombinant vectors driven by the promotor of the pet II operon, denoted pEGF-pet II, were constructed. Then, DH5α E. coli cultures containing the vector mentioned above were cultivated in Na₂S₂O₃, as this medium substantially enhances the expression of green fluorescent proteins. To examine the regulatory effect of AFE2726 on the pet II operon, the C62/V and C72/V mutants for AFE2726 were constructed in pEGF-pet II vectors using the site-directed deletion method. Compared to pEFG-pet II and pEFG-pet II-Δ-C62/V, pEFG-pet II-Δ-C72/V reduced the expression of green fluorescent proteins dramatically when transformed into DH5α E.coli in Na₂S₂O₃ medium. This suggested that the 72nd cysteine was a crucial residue of the AFE2726 protein, affecting the response of the pet II operon to sodium thiosulfate. Furthermore, the binding site of AFE2726 on the promotor of the pet II operon was identified using the electrophoretic mobility shift assay (EMSA), and it was found to be a 34bp inverted repeat sequence (named IR4), which ranged from -65 to -32. In summary, our results indicated that the AFE2726 protein regulates the pet II operon by binding to the IR4 sequence in its promotor region, whose function is likely affected by Na₂S₂O₃ binding to its Cys72 residue counterpart.

Lysophosphatidic acid-RAGE axis promotes lung and mammary oncogenesis via protein kinase B and regulating tumor microenvironment

Background

Receptor for advanced glycation end products (RAGE) is a multi-ligand transmembrane receptor of the immunoglobulin superfamily. Lysophosphatidic acid (LPA) is a ligand for RAGE and is involved in physiological and pathophysiological conditions including cancer. However, RAGE-LPA axis is unexplored in lung and mammary cancer.

Methods

RAGE was silenced in A549, MDA MB-231 and MCF7 using RAGE shRNA. For in vitro tumorigenesis, we performed wound healing, colony formation, cell proliferation and invasion assays. Evaluation of expression of oncogenes, EMT markers and downstream signaling molecules was done by using western blot and immunohistochemistry. For subcellular expression of RAGE, immunofluorescence was done. In vivo tumorigenesis was assessed by intraperitoneal injection of cancer cells in nude mice.

Results

Here we show RAGE mediated profound increase in proliferation, migration and invasion of lung and mammary cancer cells via LPA in Protein kinase B (PKB) dependent manner. LPA mediated EMT transition is regulated by RAGE. In vivo xenograft results show significance of RAGE in LPA mediated lung and mammary tumor progression, angiogenesis and immune cell infiltration to tumor microenvironment.

Conclusion

Our results establish the significance and involvement of RAGE in LPA mediated lung and mammary tumor progression and EMT transition via RAGE. RAGE-LPA axis may be a therapeutic target in lung and mammary cancer treatment strategies.

RAGE and its ligands: from pathogenesis to therapeutics

Receptor for advanced glycation end products (RAGE) is an immunoglobulin-like receptor present on cell surface. RAGE binds to an array of structurally diverse ligands, acts as a pattern recognition receptor (PRR) and is expressed on cells of different origin performing different functions. RAGE ligation leads to the initiation of a cascade of signaling events and is implicated in diseases, such as inflammation, cancer, diabetes, vascular dysfunctions, retinopathy, and neurodegenerative diseases. Because of the significant involvement of RAGE in the progression of numerous diseases, RAGE signaling has been targeted through use of inhibitors and anti-RAGE antibodies as a treatment strategy and therapy. Here in this review, we have summarized the physical and physiological aspects of RAGE biology in mammalian system and the importance of targeting this molecule in the treatment of various RAGE mediated pathologies. Highlights Receptor for advanced glycation end products (RAGE) is a member of immunoglobulin superfamily of receptors and involved in many pathophysiological conditions. RAGE ligation with its ligands leads to initiation of distinct signaling cascades and activation of numerous transcription factors. Targeting RAGE signaling through inhibitors and anti-RAGE antibodies can be promising treatment strategy.