Regulation of neutrophil function by Rac GTPases : Current Opinion in Hematology (original) (raw)
Myeloid biology
Departments of Pediatrics, Microbiology/Immunology, and Medical and Molecular Genetics, Herman B. Wells Center for Pediatric Research, James Whitcomb Riley Hospital for Children, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Correspondence to Mary C. Dinauer, MD, PhD, Departments of Pediatrics, Microbiology/Immunology, and Medical and Molecular Genetics, Herman B. Wells Center for Pediatric Research, James Whitcomb Riley Hospital for Children, Indiana University School of Medicine, 1044 W. Walnut, Room 402A, Indianapolis, IN 46202-5225, USA; e-mail: [email protected]
Abstract
Rac plays a central role in regulating neutrophil responses to inflammatory signals, including actin remodeling, chemotaxis, and superoxide production by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Rac-GTP is a component of the membrane-assembled NADPH oxidase complex, and new evidence suggests that Rac-GTP interacts directly with the oxidase flavocytochrome b, in addition to binding to the regulatory p67 phox subunit, to regulate electron transfer both independently and cooperatively from NADPH to molecular oxygen. Other new studies suggest that Rac-GTP plays a dual role in NADPH oxidase activation, and can initiate signaling pathways leading to translocation of cytosolic oxidase subunits in addition to functioning in the assembled enzyme complex. Rac activation in response to neutrophil chemoattractants may be regulated in large part by a newly identified guanine nucleotide exchange factor, P-Rex1, which is activated by either phosphatidylinositols or Gβγ subunits. Multiple Rac GTPase activating proteins are present in neutrophils and may also modulate levels of Rac-GTP. The importance of Rac in a broad range of neutrophil functions is shown by the variety of defects seen in neutrophils from Rac2 knockout mice and from a patient with recurrent infections and a dominant-negative mutation in Rac2.
© 2003 Lippincott Williams & Wilkins, Inc.