As they say, a good picture is worth a thousand words. That’s to say that I’ll have to keep the introduction short in this post (!) to let you know about this interesting map from Boster Bio summarizing the allergic response pathway. I’ll take this opportunity to mention a few related immunoassays that may help you deciphering this pathway in your own study!

Glycocalyx, literally meaning ‘sugar coat’, is an extracellular polymeric coating surrounding many prokaryotic and eukaryotic cells that consists of glycoproteins, glycolipids, proteoglycans and glycosaminoglycans. The constituents of the glycocalyx play an important role in the process of cell signaling, virus transfection, and immunity and glycosylation status is important in processes such as inflammation and tumour microenvironment. However, the range of detection tools available for glycobiology research is quite limited, and in most cases, studies aimed at characterising glycosylation patterns have to be done with HPLC using home-based methods.

In a previous post, we discussed about how important it is to have research tools that allow to study secretome biomarkers outside the usual human and rodents. Either because other species are important research models, or more importantly, because they are the final patient that will be treated, such as pets or cattle.

miRNAs are key mediators in cell processes, allowing to activate or inhibit the expression of certain genes important in different physiological processes. How miRNAs work, and which ones are relevant, are a hot topic of research nowadays, and important advances are being made in areas such as Oncology and the Immune response.

ISG15 ubiquitin-like modifier (ISG15) functions intracellularly as a Ubiquitin homologue and a cytokine. ISG15 induces production of IFN-gamma and augments NK/lymphokine-activated killer cell proliferation and function. Secreted from monocytes and lymphocytes, low levels of ISG15 are present constitutively in PBMCs. Interestingly, a dose-dependent ISG15 synthesis has been observed in response to IFN-alpha or IFN-beta, but not IFN-gamma.

Control (C) and Treated (T) 40 μg lysate samples from A549, Ovcar and HeLa cells were run alongside 50 ng recombinant ISG15 and 100 μg ubiquitin. Cells were either untreated (C) or treated (T) with 1000 U/ml of Human IFN beta 1a (Cat. No. 09311410-2) and lysed with protease inhibitors on ice, then centrifuged to obtain supernatants. No cross-reactivity was observed with ubiquitin at tested concentrations up to 100 μg. The antibody (Cat. No. 09321900-1) was additionally tested on Daudi and U937 cell lysates (data not shown).

For instance, ISG15 is secreted in response to IFN-beta treatment in vitro in healthy volunteers, as seen by measuring ISG15 serum levels (1). A process mediated by ISG15, ISGylation, has been described to have a role in immunomodulation after bacterial infection (2). HCV also induces ISG15 expression (3).

Briefly, ISG15 expression seems to regulate, at least in part, Type I interferon signaling, translation, chromatin remodeling, cell motility, protein trafficking, and protein conjugation (ISGylation). Still, the complete spectrum of ISG15-dependent biological sequelae re-mains to be fully elucidated.

Further characterization of new ISG15 target proteins and the role of free ISG15 may offer new insights into mechanistic and immuno-therapeutic approaches to human diseases.

Tools to detect ISG15 should be able to detect both bound and free-ISG15, and have no cross-reactivity with ubiquitin (e.g. anti-human ISG15, clone 2.1), as this may hinder the interpretation of results found with biological samples.

References

1. D’Cunha, J. et al.  Journal of Immunology, 1996, 157:4100.
2. Dieterich, C. & Relman, D.A. PLoS ONE 6(11): e27535. doi:10.1371/journal.pone.0027535.
3. Arnaud, N. et al. PLoS Pathog, 2011, 7(10): e1002289. doi: 10.1371/journal.ppat.1002289.

Studying the role of ISG15 in your experimental model?

Leave a comment regarding the research tools you are using to investigate the role of ISG15 in IFN signaling pathway !