Dysfunction of the PI3 kinase/Rap1/integrin αIIbβ3 pathway underlies ex vivo platelet hypoactivity in essential thrombocythemia

Samantha F Moore, Roger W Hunter, Matthew T Harper, Joshua S Savage, Samreen Siddiq, Sarah K Westbury, Alastair W Poole, Andrew D Mumford, Ingeborg Hers

Research output: Contribution to journalArticle (Academic Journal)

26 Citations (Scopus)

Abstract

Patients with myeloproliferative disorders (MPD) such as essential thrombocythemia (ET) have increased risk of thrombosis and bleeding, which are major sources of morbidity and mortality. Most MPD patients have a gain of function mutation in Janus kinase 2 (JAK2V617F), but little is known how JAK2V617F affects platelet function. Here, we demonstrate that platelets from ET patients have impaired SFLLRN-mediated fibrinogen binding and have lost the potentiating effect of thrombopoietin (which couples to JAK2) on this pathway. In contrast, SFLLRN- mediated P-selectin expression, ATP secretion, phosphorylation of the PKC substrate pleckstrin and Ca2+ mobilisation were unaffected in JAK2V617F positive platelets.
In addition, thrombopoietin-mediated JAK2 phosphorylation was unchanged, suggesting that signalling pathways activated downstream of JAK2 are impaired. Indeed, we found that platelets from JAK2V617F positive ET patients have significantly reduced phosphorylation of the PI3 kinase substrate Akt, and have reduced activation of Rap1 in response to thrombopoietin, IGF-1, ADP, SFLLRN and thrombin. This effect was independent of Giα P2Y12 purinergic receptor function as ADP-mediated inhibition of VASP phosphorylation was unchanged. These results demonstrate that the PI3 kinase/Rap1 pathway is intrinsically impaired in platelets from JAK2V617F positive ET patients, resulting in diminished thrombin and thrombopoietin- mediated integrin αIIbβ3 activation.
Original languageEnglish
Pages (from-to)1209-19
Number of pages11
JournalBlood
Volume121
Issue number7
Early online date4 Dec 2012
DOIs
Publication statusPublished - 2013

Fingerprint Dive into the research topics of 'Dysfunction of the PI3 kinase/Rap1/integrin αIIbβ3 pathway underlies ex vivo platelet hypoactivity in essential thrombocythemia'. Together they form a unique fingerprint.

Cite this