At the outset of our project, we had just been able to demonstrate that the tyrosine nitration of SERCA-2 was at least partially responsible for the increase in platelet Ca2+ and in the activity of calpains (Ca2+ -dependent cysteine proteases) in platelets from individuals with diabetes. During the course of the grant, we collaborated intensively with project Z01 to identify the changes in the platelet proteome that were elicited by diabetes and attributable to calpain; in particular septin 5 and the ILK-PINCH-Parvin complex. It was also possible to show that the inhibition of calpain in a mouse mode of diabetes prevented the development of platelet hyper-reactivity associated with the disease. Added to that calpain inhibition also prevented the endothelial dysfunction associated with diabetes, largely by preventing the proteolysis of prostacyclin-synthase. Circulating microRNAs are also altered in diabetes and it was possible to link the activation of calpain to the cleavage of Dicer and a marked alteration in the platelet miRNA profile – changes again prevented in animals treated with a calpain inhibitor. Focussing on the actions of one micro-RNA, we demonstrated that miR-223 plays a key role in regulating platelet function by regulating the expression of key regulators of platelet function including β1 integrin and factor XIII. Finally, in what started as a collaborative project with project A07, it was possible to demonstrate that the activity of cystathionine-γ-lyase (CSE), is an important endogenous regulator of vascular function. We found that the H2S generated by the enzyme in endothelial cells sulfhydrated and inactivated the RNA-binding protein HuR, preventing it interacting and stabilizing its target mRNAs (one of which was CD62E). In atherosclerosis, vascular inflammation resulted in the phosphorylation and inhibition of CSE and the loss of this protective mechanism, resulting in an increase in CD62E expression, monocytes adhesion and accelerated atherosclerosis in animals specifically lacking CSE in endothelial cells.

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Institut für Vaskular Signalling (http://www.ivs.uni-frankfurt.de/)