Platelets are key players in hemostasis and thrombosis. Essential thrombocythemia (ET) is a myeloproliferative neoplasm (MPN) in which the JAK2 V617F, MPL W515K/L, and CALR mutations determine differences in clinical phenotype, in particular the thrombotic risk and the risk of myelofibrosis. Here, we examined the proteome of platelets in ET by mass spectrometry (MS) in combination with functional assays to gain insights into platelet activation in ET. MS analysis revealed a different proteome in ET platelets with stoichiometric differences in mitochondrial proteins compared with normal platelets. The tricarboxylic acid cycle enzymes (TCA) were in general downregulated in ET platelets while glycolysis enzymes were upregulated changing modes in energy production. Acetyl salicylic acid (ASA) treatment increased levels of TCA enzymes in controls and restored them only partially in JAK2 V617F platelets. Interestingly, membrane CD36 was higher in CALR Type1 implicating lipid transport and fatty acid oxidation in platelet lifespan. Aggregation levels specifically in JAK2 V617F platelets were similar or lower to healthy controls while activation markers i.e. CD62P were higher in untreated CALR Type2 than controls and the rest of ET. In summary, analysis of platelet proteome in ET implicates mitochondrial activity in platelet activation and also identified differences between JAK2 V617F and CALR patients. Our study suggests that metabolic finetuning can be critical in the control of platelet reactivity.

The authors have declared no competing interest.

This study was supported by funds from the Comunidad de Madrid, Atraccion de Talento (2016-T1/BMD-1051 and 2020-5A/BMD-19731 to P.P), the Stichting tegen Kanker (C/2014/302 to P.V) and Research Foundation_Flanders (FWO, G.0908.15 to P.V)

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics Committee of the University Hospital Leuven (study number S53745), and the Hospital Clinico San Carlos (Madrid, C.P - C.I. 16/257-E_BS) gave approval for this work.

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The raw files and processed proteomics data of two independent experiments have been deposited to the ProteomeXchange Consortium via the PRIDE (13) partner repository with the dataset identifiers PXD052171 and PXD050550.

https://proteomecentral.proteomexchange.org/ui