Cloning and functional characterization of recombinant equine P-selectin.

This research explores the role of a specific protein called P-selectin in white blood cell movement in horses. The team generated a modified version of the protein and showed that it not only influences adhesion, but also activates certain cellular processes and, its interaction with its ligand, PSGL-1, is key for these activities. This modified protein may be useful for further studies on inflammation in horses.

Cloning and Functional Characterization of Recombinant Equine P-selectin

The researchers conducted a detailed study into the nature and function of equine P-selectin (ePsel), a protein that plays a crucial role in the movement of leukocytes (white blood cells).

• They genetically engineered a chimeric protein that combines elements of ePsel and immunoglobulin G (IgG).
• The resulting ePsel-IgG was presented in a soluble form and was found to bind to equine monocytes (a type of white blood cell), an action observable by confocal microscopy and flow cytometry.

Chimeric ePsel-IgG Effects on Equine Monocytes

Further studies looked at the effect of this chimeric protein on equine monocytes.

• The binding of ePsel-IgG to monocytes was found to be dose-dependent and evolved over a certain time course.
• Moreover, ePsel-IgG played a dual role – it not only acted as an adhesion molecule but also triggered cellular signalling by activating a type of protein kinase known as ERK1/2 and inducing expression of a cytokine (interleukin-8).

P-Selectin and PSGL-1 Interaction

Interestingly, all of these effects could be negated by introducing EDTA, a chelating agent, and thereby suggesting that the interactions of ePsel-IgG were mediated by P-selectin ligand, PSGL-1 itself.

• 78% of equine monocytes were shown to cross-react with an anti-human antibody, recognising a well-known carbohydrate-binding site found on human PSGL-1.
• Pre-treatment with certain enzymes reduced the binding of ePsel-IgG to monocytes significantly, suggesting that P-selectin recognises two ligand sites – one being the carbohydrate binding site and the other core protein of the PSGL-1.

Conclusion and Future Implications

The study provides insight into the role of equine P-selectin in leukocyte trafficking and cellular signalling in horses. The chimeric protein ePsel-IgG provides a useful tool for further research into equine P-selectin and its involvement in inflammatory responses in horses.