Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation

Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation

^*Bonfils Blood Center, Denver, CO 80220; ^†Department of Pediatrics, and ^§Pharmacology, University of Colorado Health Sciences Center, Denver, CO 80262; ^¶Departments of Pediatric Hematology/Oncology and Surgery, Rhode Island Hospital, Providence, RI 02903; ^‖Central Laboratory of the Netherlands Blood Transfusion Service and Laboratory of Experimental and Clinical Immunology, Academic Medical Center, Amsterdam, The Netherlands; and ^**Clinical Labs, National Jewish Medical and Research Center, Denver, CO 80206

Communicated by Henry R. Bourne, University of California, San Francisco, CA (received for review December 22, 1999)

Abstract

A 5-week-old male infant presented with severe bacterial infections and poor wound healing, suggesting a neutrophil defect. Neutrophils from this patient exhibited decreased chemotaxis, polarization, azurophilic granule secretion, and superoxide anion (O₂ ⁻) production but had normal expression and up-regulation of CD11b. Rac2, which constitutes >96% of the Rac in neutrophils, is a member of the Rho family of GTPases that regulates the actin cytoskeleton and O₂ ⁻ production. Western blot analysis of lysates from patient neutrophils demonstrated decreased levels of Rac2 protein. Addition of recombinant Rac to extracts of the patient neutrophils reconstituted O₂ ⁻ production in an in vitro assay system. Molecular analysis identified a point mutation in one allele of the Rac2 gene resulting in the substitution of Asp57 by an Asn (Rac2^D57N). Asp57 is invariant in all defined GTP-binding proteins. Rac2^D57N binds GDP but not GTP and inhibits oxidase activation and O₂ ⁻ production in vitro. These data represent the description of an inhibitory mutation in a member of the Rho family of GTPases associated with a human immunodeficiency syndrome.

Footnotes

↵ ‡ To whom reprint requests should be addressed at: Bonfils Blood Center, 717 Yosemite Circle, Denver, CO 80230. E-mail: daniel.ambruso{at}UCHSC.edu.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.080074897.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.080074897
Abbreviations:

PMA,

phorbol myristate acetate;

PAF,

platelet-activating factor;

fMLP,

formyl-methionyl, leucyl-phenylalanine;

LAD,

;

MPO,

myeloperoxidase;

SOD,

superoxide dismutase;

GTP[γS],

guanosine 5′-[γ-thio]triphosphate;

GST,

glutathione S-transferase;

EBV,

Epstein–Barr virus