JAK2-V617F promotes venous thrombosis through β1/β2 integrin activation
Bärbel Edelmann, … , Andreas J. Müller, Thomas Fischer
Bärbel Edelmann, … , Andreas J. Müller, Thomas Fischer
Published July 19, 2018
Citation Information: J Clin Invest. 2018;128(10):4359-4371. https://doi.org/10.1172/JCI90312.
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Research Article Hematology

JAK2-V617F promotes venous thrombosis through β1/β2 integrin activation

Abstract

JAK2-V617F–positive chronic myeloproliferative neoplasia (CMN) commonly displays dysfunction of integrins and adhesion molecules expressed on platelets, erythrocytes, and leukocytes. However, the mechanism by which the 2 major leukocyte integrin chains, β1 and β2, may contribute to CMN pathophysiology remained unclear. β1 (α4β1; VLA-4) and β2 (αLβ2; LFA-1) integrins are essential regulators for attachment of leukocytes to endothelial cells. We here showed enhanced adhesion of granulocytes from mice with JAK2-V617F knockin (JAK2+/VF mice) to vascular cell adhesion molecule 1– (VCAM1-) and intercellular adhesion molecule 1–coated (ICAM1-coated) surfaces. Soluble VCAM1 and ICAM1 ligand binding assays revealed increased affinity of β1 and β2 integrins for their respective ligands. For β1 integrins, this correlated with a structural change from the low- to the high-affinity conformation induced by JAK2-V617F. JAK2-V617F triggered constitutive activation of the integrin inside-out signaling molecule Rap1, resulting in translocation toward the cell membrane. Employing a venous thrombosis model, we demonstrated that neutralizing anti–VLA-4 and anti–β2 integrin antibodies suppress pathologic thrombosis as observed in JAK2+/VF mice. In addition, aberrant homing of JAK2+/VF leukocytes to the spleen was inhibited by neutralizing anti-β2 antibodies and by pharmacologic inhibition of Rap1. Thus, our findings identified cross-talk between JAK2-V617F and integrin activation promoting pathologic thrombosis and abnormal trafficking of leukocytes to the spleen.

Authors

Bärbel Edelmann, Nibedita Gupta, Tina M. Schnoeder, Anja M. Oelschlegel, Khurrum Shahzad, Jürgen Goldschmidt, Lars Philipsen, Soenke Weinert, Aniket Ghosh, Felix C. Saalfeld, Subbaiah Chary Nimmagadda, Peter Müller, Rüdiger Braun-Dullaeus, Juliane Mohr, Denise Wolleschak, Stefanie Kliche, Holger Amthauer, Florian H. Heidel, Burkhart Schraven, Berend Isermann, Andreas J. Müller, Thomas Fischer

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Figure 7

Increased adhesiveness and homing capacity to the spleen of primary JAK2+/VF murine myeloid cells.

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Increased adhesiveness and homing capacity to the spleen of primary JAK2...
(A) Volume-rendered whole-body SPECT/CT images of a mouse injected with 111indium-labeled JAK2+/VF WBM cells compared with a control mouse injected with 111indium-labeled JAK2+/+ cells. Representative SPECT images (pseudocolored) are overlaid on CT images (gray scale) (left panel). Mice were injected with a CT contrast agent. Units in the color scale for the SPECT images are standardized uptake values (SUV). SUV were 9.7 for mice (n = 4) injected with JAK2+/+ cells compared with 15.1 for mice (n = 5) injected with JAK2+/VF cells (right panel). (B) WBM cells of 10- to 12-week-old JAK2+/VF or JAK2+/+ mice (carrying the congenic marker CD45.2) were injected into CD45.1 recipient mice. Sixteen hours after injection, spleens of recipient mice were evaluated. Data represent number of detected CD45.2-positive granulocytes and monocytes per 106 cells in the spleen (n = 14/group) and are shown as mean ± SEM. *P ≤ 0.05 (unpaired, 2-tailed Student’s t test). (C) Effect of β2 integrin blocking antibody treatment (50 μg/ml; 30 minutes, n = 9) compared with isotype-treated cells (n = 10) on the number of detected CD45.2-positive granulocytes and monocytes per 106 spleen cells 16 hours after tail vein injection. (D) Effect of GGTI-2147 treatment (10 μM; 30 minutes) on the number of detected CD45.2-positive granulocytes and monocytes per 106 spleen cells 16 hours after tail vein injection (–GGTI-2147, n = 10 and +GGTI-2147, n = 9); 0 indicates DMSO control (left panel). Data shown as mean ± SEM. *P ≤ 0.05, **P ≤ 0.01 (nonparametric Mann-Whitney U test).