Constitutive activation of WASp in X-linked neutropenia renders neutrophils hyperactive
Marton Keszei, … , Scott B. Snapper, Lisa S. Westerberg
Marton Keszei, … , Scott B. Snapper, Lisa S. Westerberg
Published August 20, 2018
Citation Information: J Clin Invest. 2018;128(9):4115-4131. https://doi.org/10.1172/JCI64772.
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Research Article Immunology

Constitutive activation of WASp in X-linked neutropenia renders neutrophils hyperactive

Abstract

Congenital neutropenia is characterized by low absolute neutrophil numbers in blood, leading to recurrent bacterial infections, and patients often require life-long granulocyte CSF (G-CSF) support. X-linked neutropenia (XLN) is caused by gain-of-function mutations in the actin regulator Wiskott-Aldrich syndrome protein (WASp). To understand the pathophysiology in XLN and the role of WASp in neutrophils, we here examined XLN patients and 2 XLN mouse models. XLN patients had reduced myelopoiesis and extremely low blood neutrophil number. However, their neutrophils had a hyperactive phenotype and were present in normal numbers in XLN patient saliva. Murine XLN neutrophils were hyperactivated, with increased actin dynamics and migration into tissues. We provide molecular evidence that the hyperactivity of XLN neutrophils is caused by WASp in a constitutively open conformation due to contingent phosphorylation of the critical tyrosine-293 and plasma membrane localization. This renders WASp activity less dependent on regulation by PI3K. Our data show that the amplitude of WASp activity inside a cell could be enhanced by cell-surface receptor signaling even in the context in which WASp is already in an active conformation. Moreover, these data categorize XLN as an atypical congenital neutropenia in which constitutive activation of WASp in tissue neutrophils compensates for reduced myelopoiesis.

Authors

Marton Keszei, Julien Record, Joanna S. Kritikou, Hannah Wurzer, Chiara Geyer, Meike Thiemann, Paul Drescher, Hanna Brauner, Laura Köcher, Jaime James, Minghui He, Marisa A.P. Baptista, Carin I.M. Dahlberg, Amlan Biswas, Sonia Lain, David P. Lane, Wenxia Song, Katrin Pütsep, Peter Vandenberghe, Scott B. Snapper, Lisa S. Westerberg

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Figure 4

Increased rate of migration of WASp L272P and WASp I296T neutrophils to the spleen and to the inflammation site in vivo.

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Increased rate of migration of WASp L272P and WASp I296T neutrophils to ...
(A) Neutrophil numbers in ears of WT and WASp L272P mice 6 hours after induction of dermatitis with S. aureus (106 CFU) injection. Data are shown as mean ± SEM. Unpaired, 2-tailed Student’s t test. WT, n = 8; WASp L272P, n = 8/group. (B) WT and WASp I296T neutrophil numbers in peritoneum 24 hours after injection of S. aureus (20 × 106 CFU). Data are shown as mean ± SEM. Unpaired, 2-tailed Student’s t test. WT, n = 7; WASp I296T, n = 7/group. (C) WASp L272P/CD45.1 WT (left panel) and WASp I296T/CD45.1 WT (right panel) neutrophil ratios in various organs in mixed bone marrow chimera mice were normalized with their original bone marrow reconstitution ratio (CD45.2/CD45.1) and plotted with logarithmic scale. Data are shown as mean ± SEM, 1-way ANOVA with Bonferroni’s correction. WASp L272P/CD45.1: WT, n = 9 (bone); n = 22 (blood); n = 11 (spleen); n = 7 (peritoneum); WASp I296T/CD45.1: WT n = 14 (bone); n = 21 (blood); n = 14 (spleen); n = 7/group (peritoneum). (D) In vivo homing of WASp L272P (CD45.2), WASp I296T (CD45.2), and CD45.1 WT cells into various tissues was measured 5 hours after i.v. injection of bone marrow neutrophil grafts. Graft neutrophils (CD45.1+ or CD45.2+ single positive) were counted in blood, bone marrow, spleen, and air pouch lavage. The normalization formula is explained in Methods. Pool of at least 2 experiments per genotype. Data are shown as mean ± SEM, 1-way ANOVA with Bonferroni’s correction. WT, n = 12; WASp I296T, n = 20; WASp L272P, n = 21; WKO, n = 6/group.