New insights into platelet activation

In a new study in the journal "Blood", ISAS scientists again looked into the process of platelet activation. This time they focused on the dynamic signalling cascades that take place during the first seconds after activation and need to be analysed with high temporal resolution. By applying temporally resolved methods, new target molecules can be identified for novel therapeutic interventions in thrombosis treatment or for thrombosis risk identification.

In their experiments the researchers examined the effects of ADP (adenosine diphosphate), a molecule with a crucial role in many signalling cascades that are mediated by protein phosphorylation. In platelets, ADP triggers aggregation and thus initiates blood clotting. On the other hand, prostacyclin and related molecules can inhibit this process. These two signalling pathways are the main targets of modern anti-thrombosis drugs, so called platelet aggregation inhibitors.

In their study, the scientists from the Protein Dynamics group analysed the signalling cascades triggered by ADP and Iloprost, a prostacyclin-related inhibitor that is used to treat high blood pressure. They generated time-resolved profiles of more than 4700 phosphopeptides and were able to demonstrate that the most important events occur during the first ten seconds after ADP stimulation – a time range that cannot be covered with current methods. Therefore, improved sampling methods will also be needed in future. Furthermore, many changes were transient rather than long-lasting, indicating that many steps in the signalling pathways might have been simply overlooked so far.  On the whole, the scientists found significant effects of ADP or Iloprost on about 600 proteins, proving the enormous complexity of the investigated pathways. They also developed so called targeted MS assays for numerous phosphorylation sites to specifically analyse them via mass spectrometry, without having to use antibodies. Furthermore, the study revealed several previously unknown key proteins for platelet activation.