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JAK2V617F activates Lu/BCAM-mediated red cell adhesion in polycythemia vera through an EpoR-independent Rap1/Akt pathway.: JAK2V617F activates Lu/BCAM through Rap1/Akt

Abstract : Polycythemia vera (PV) is characterized by an increased RBC mass, spontaneous erythroid colony formation, and the JAK2V617F mutation. PV is associated with a high risk of mesenteric and cerebral thrombosis. PV RBC adhesion to endothelial laminin is increased and mediated by phosphorylated erythroid Lu/BCAM. In the present work, we investigated the mechanism responsible for Lu/BCAM phosphorylation in the presence of JAK2V617F using HEL and BaF3 cell lines as well as RBCs from patients with PV. High levels of Rap1-GTP were found in HEL and BaF3 cells expressing JAK2V617F compared with BaF3 cells with wild-type JAK2. This finding was associated with increased Akt activity, Lu/BCAM phosphorylation, and cell adhesion to laminin that were inhibited by the dominant-negative Rap1S17N or by the specific Rap1 inhibitor GGTI-298. Surprisingly, knocking-down EpoR in HEL cells did not alter Akt activity or cell adhesion to laminin. Our findings reveal a novel EpoR-independent Rap1/Akt signaling pathway that is activated by JAK2V617F in circulating PV RBCs and responsible for Lu/BCAM activation. This new characteristic of JAK2V617F could play a critical role in initiating abnormal interactions among circulating and endothelial cells in patients with PV.
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https://www.hal.inserm.fr/inserm-00821109
Contributor : Wassim El Nemer <>
Submitted on : Tuesday, May 7, 2013 - 3:02:29 PM
Last modification on : Tuesday, September 1, 2020 - 3:07:37 AM

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Maria de Grandis, Marie Cambot, Marie-Paule Wautier, Bruno Cassinat, Christine Chomienne, et al.. JAK2V617F activates Lu/BCAM-mediated red cell adhesion in polycythemia vera through an EpoR-independent Rap1/Akt pathway.: JAK2V617F activates Lu/BCAM through Rap1/Akt. Blood, American Society of Hematology, 2013, 121 (4), pp.658-65. ⟨10.1182/blood-2012-07-440487⟩. ⟨inserm-00821109⟩

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