151
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Abstract
Reactive oxygen species (ROS) have been increasingly recognized as important components of cell signaling in addition to their well-established roles in host defense. The formation of ROS in phagocytic and nonphagocytic cells involves membrane-localized and Rac guanosine triphosphatase (GTPase)-regulated reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase(s). We discuss here the current molecular models for Rac GTPase action in the control of the phagocytic leukocyte NADPH oxidase. As a mechanistically detailed example of Rac GTPase signaling, the NADPH oxidase provides a potential paradigm for signaling by Rho family GTPases in general.
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Affiliation(s)
- Gary M Bokoch
- Departments of Immunology and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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152
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Yoshida L, Nishida S, Shimoyama T, Kawahara T, Rokutan K, Tsunawaki S. Expression of a p67(phox) homolog in Caco-2 cells giving O(2)(-)-reconstituting ability to cytochrome b(558) together with recombinant p47(phox). Biochem Biophys Res Commun 2002; 296:1322-8. [PMID: 12207919 DOI: 10.1016/s0006-291x(02)02059-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Human normal and transformed (Caco-2) colon tissues as well as guinea pig gastric mucosal cells express Nox1, which is a homolog of the phagocyte NADPH oxidase subunit, gp91(phox) of membrane-bound cytochrome b(558). It was reported that Nox1-transfection to NIH 3T3 cells could provide O(2)(-)-generating ability, independently of regulatory cytosolic factors (Rac2, p67(phox), and p47(phox)) that are obligatory in the phagocyte oxidase system. Here, we detected and sequenced a p67(phox) homolog in Caco-2 almost identical to the neutrophil sequence, except for three nucleotide substitutions, two of which changed lysines 181 and 328 to arginines. Investigation of its ability to support O(2)(-)-generation in cell-free reconstitution experiments combining with neutrophil cytochrome b(558) showed O(2)(-)-generation, provided that recombinant p47(phox) was added. This result demonstrates that the intrinsic p67(phox) homolog of Caco-2 was able to function as a phagocyte p67(phox) for cytochrome b(558). The requirement of p47(phox) addition suggested that this component was absent in Caco-2 cells. Caco-2 membranes, used as a source of Nox1 in place of cytochrome b(558), did not show significant O(2)(-)-generation, which was mainly explained by their very little Nox1 expression.
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Affiliation(s)
- L Yoshida
- Department of Infectious Diseases, National Research Institute for Child Health and Development, 3-35-31, Taishido, Setagaya, 154-8567, Tokyo, Japan
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153
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Rabiet MJ, Tardif M, Braun L, Boulay F. Inhibitory effects of a dominant-interfering form of the Rho-GTPase Cdc42 in the chemoattractant-elicited signaling pathways leading to NADPH oxidase activation in differentiated HL-60 cells. Blood 2002; 100:1835-44. [PMID: 12176907 DOI: 10.1182/blood-2001-12-0193] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A tetracycline-controlled expression system was adapted to the human promyelocytic HL-60 cell line by placement of the transactivator (tTA-off) sequence under the control of the human EF-1alpha promoter region. Constitutively active and dominant-inhibitory forms of Cdc42 (Cdc42V12 and Cdc42N17, respectively) were conditionally expressed in this system. The expression of Cdc42V12 had no marked effect on chemoattractant-mediated superoxide production, corroborating previous results indicating that the guanosine 5'-triphosphate (GTP)-bound form of Cdc42 is ineffective in directly activating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in a cell-free system. However, the N17 mutant potently inhibited chemoattractant-induced superoxide production. The expression of Cdc42N17 interfered with the GTP-loading of Rac and Ras and with the activation of the MAP-kinase pathway. A drastic reduction of chemoattractant-induced inositol-1,4,5-trisphosphate formation and calcium mobilization was observed, corroborating previous in vitro study results identifying PLCbeta2 as a Rac/Cdc42 effector. Cdc42N17 was also found to inhibit the translocation of Ras-GRF2, a guanine nucleotide exchange factor for Ras and Rac but not for Cdc42. Thus, the dominant-inhibitory mutant Cdc42N17 was found to interfere at multiple levels in the signaling pathways. The pleiotropic inhibitory effects of Cdc42N17 illustrate the potential pitfalls of using dominant-inhibitory proteins to study the function of Ras-family GTPases. In this regard, a number of conclusions drawn from the use of dominant-inhibitory mutants in myeloid cells might have to be reconsidered.
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Affiliation(s)
- Marie-Josèphe Rabiet
- Département Réponse et Dynamique Cellulaires/Biochimie et Biophysique des Systèmes Intégrés, Grenoble, France.
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154
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Yamamori T, Inanami O, Sumimoto H, Akasaki T, Nagahata H, Kuwabara M. Relationship between p38 mitogen-activated protein kinase and small GTPase Rac for the activation of NADPH oxidase in bovine neutrophils. Biochem Biophys Res Commun 2002; 293:1571-8. [PMID: 12054696 DOI: 10.1016/s0006-291x(02)00418-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Superoxide production by NADPH oxidase is essential for bactericidal properties of neutrophils. However, molecular mechanisms underlying the activation of this enzyme remain largely unknown. Here, using bovine neutrophils we examined the role of p38 mitogen-activated protein kinase (p38 MAPK) in the signaling pathways of the NADPH oxidase activation. Superoxide production was induced by stimulation with serum-opsonized zymosan (OZ) and attenuated by p38 MAPK inhibitor, SB203580. OZ stimulation induced the translocation of p47(phox) and Rac to the plasma membrane and SB203580 completely blocked the translocation of Rac, but only partially blocked that of p47(phox). Furthermore, SB203580 abolished the OZ-elicited activation of Rac, which was assessed by detecting the GTP-bound form of this protein. Phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin and LY294002, blocked not only p38 MAPK activation but also Rac activation. However, SB203580 showed no effect on the PI3K activity. These results suggested that PI3K/p38 MAPK/Rac pathway was present in the activation of NADPH oxidase in bovine neutrophils.
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Affiliation(s)
- Tohru Yamamori
- Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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155
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Price MO, Atkinson SJ, Knaus UG, Dinauer MC. Rac activation induces NADPH oxidase activity in transgenic COSphox cells, and the level of superoxide production is exchange factor-dependent. J Biol Chem 2002; 277:19220-8. [PMID: 11896053 DOI: 10.1074/jbc.m200061200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient expression of constitutively active Rac1 derivatives, (G12V) or (Q61L), was sufficient to induce phagocyte NADPH oxidase activity in a COS-7 cell model in which human cDNAs for essential oxidase components, gp91(phox), p22(phox), p47(phox), and p67(phox), were expressed as stable transgenes. Expression of constitutively active Rac1 in "COS(phox)" cells induced translocation of p47(phox) and p67(phox) to the membrane. Furthermore, translocation of p47(phox) was induced in the absence of p67(phox) expression, even though Rac does not directly bind p47(phox). Rac effector domain point substitutions (A27K, G30S, D38A, Y40C), which can selectively eliminate interaction with different effector proteins, impaired Rac1V12-induced superoxide production. Activation of endogenous Rac1 by expression of constitutively active Rac-guanine nucleotide exchange factor (GEF) derivatives was sufficient to induce high level NADPH oxidase activity in COS(phox) cells. The constitutively active form of the hematopoietic-specific GEF, Vav1, was the most effective at activating superoxide production, despite detection of higher levels of Rac1-GTP upon expression of constitutively active Vav2 or Tiam1 derivatives. These data suggest that Rac can play a dual role in NADPH oxidase activation, both by directly participating in the oxidase complex and by activating signaling events leading to oxidase assembly, and that Vav1 may be the physiologically relevant GEF responsible for activating this Rac-regulated complex.
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Affiliation(s)
- Marianne O Price
- Herman B Wells Center for Pediatric Research, Department of Pediatrics (Hematology/Oncology), James Whitcomb Riley Hospital for Children, Indiana University Medical Center, Indianapolis, Indiana 46202, USA
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156
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Lapouge K, Smith SJM, Groemping Y, Rittinger K. Architecture of the p40-p47-p67phox complex in the resting state of the NADPH oxidase. A central role for p67phox. J Biol Chem 2002; 277:10121-8. [PMID: 11796733 DOI: 10.1074/jbc.m112065200] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The phagocyte NADPH oxidase is a multiprotein enzyme whose subunits are partitioned between the cytosol and plasma membrane in resting cells. Upon exposure to appropriate stimuli multiple phosphorylation events in the cytosolic components take place, which induce rearrangements in a number of protein-protein interactions, ultimately leading to translocation of the cytoplasmic complex to the membrane. To understand the molecular mechanisms that underlie the assembly and activation process we have carried out a detailed study of the protein-protein interactions that occur in the p40-p47-p67(phox) complex of the resting oxidase. Here we show that this complex contains one copy of each protein, which assembles to form a heterotrimeric complex. The apparent high molecular weight of this complex, as observed by gel filtration studies, is due to an extended, non-globular shape rather than to the presence of multiple copies of any of the proteins. Isothermal titration calorimetry measurements of the interactions between the individual components of this complex demonstrate that p67(phox) is the primary binding partner of p47(phox) in the resting state. These findings, in combination with earlier reports, allow us to propose a model for the architecture of the resting complex in which p67(phox) acts as the bridging molecule that connects p40(phox) and p47(phox).
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Affiliation(s)
- Karine Lapouge
- Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
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157
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Gauss KA, Mascolo PL, Siemsen DW, Nelson LK, Bunger PL, Pagano PJ, Quinn MT. Cloning and sequencing of rabbit leukocyte NADPH oxidase genes reveals a unique p67
phox
homolog. J Leukoc Biol 2002. [DOI: 10.1189/jlb.71.2.319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Katherine A. Gauss
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
| | - Patrice L. Mascolo
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
| | - Daniel W. Siemsen
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
| | - Laura K. Nelson
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
| | - Peggy L. Bunger
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
| | - Patrick J. Pagano
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan
| | - Mark T. Quinn
- Department of Veterinary Molecular Biology, Montana State University, Bozeman; and
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158
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Alloul N, Gorzalczany Y, Itan M, Sigal N, Pick E. Activation of the superoxide-generating NADPH oxidase by chimeric proteins consisting of segments of the cytosolic component p67(phox) and the small GTPase Rac1. Biochemistry 2001; 40:14557-66. [PMID: 11724569 DOI: 10.1021/bi0117347] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation of the superoxide (O2(-))-generating NADPH oxidase of phagocytes is the consequence of the assembly of a membrane-associated flavocytochrome b(559) with the cytosolic proteins p47(phox) and p67(phox) and the small GTPase Rac (1 or 2). We proposed that Rac1 serves as a membrane-targeting molecule for p67(phox). This hypothesis was tested by constructing recombinant chimeric proteins, joining various functional domains of p67(phox) and Rac1, and expressing these in Escherichia coli. Chimeras were assayed for the ability to support O2(-) production by phagocyte membranes in an amphiphile-activated cell-free system in the presence or absence of p47(phox). A chimera consisting of p67(phox) truncated at residue 212 and fused to a full-length Rac1 [p67(phox)(1-212)-Rac1(1-192)] was a potent NADPH oxidase activator. A p67(phox)(1-212)-Rac1(178-192) chimera, to which Rac1 contributed only the C-terminal polybasic domain, was a weaker but consistent activator. Chimeras comprising the full length of Rac1 bound GTP/GDP, like bona fide GTPases. The activity of p67(phox)-Rac1 chimeras was dependent on the presence of the tetratricopeptide repeat and activation domains, in the p67(phox) segment, and on an intact polybasic region, at the C terminus of the Rac1 segment, but not on the insert region of Rac1. Partial activation by chimeras, in the GTP-bound form, was also possible in the absence of p47(phox). Evidence is offered in support of the proposal that the GTP- and GDP-bound forms of chimera p67(phox)(1-212)-Rac1(1-192) have distinct conformations, corresponding to the presence and absence of intrachimeric bonds, respectively.
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Affiliation(s)
- N Alloul
- The Julius Friedrich Cohnheim-Minerva Center for Phagocyte Research and the Ela Kodesz Institute of Host Defense against Infectious Diseases, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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159
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Miyano K, Ogasawara S, Han CH, Fukuda H, Tamura M. A fusion protein between rac and p67phox (1-210) reconstitutes NADPH oxidase with higher activity and stability than the individual components. Biochemistry 2001; 40:14089-97. [PMID: 11705402 DOI: 10.1021/bi010882u] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Activation of the phagocyte NADPH oxidase, a superoxide-generating enzyme, involves assembly of cytosolic p47(phox), p67(phox), and rac with the membrane-associated cytochrome b(558). Following cell-free activation, enzymatic activity is highly labile [Tamura, M., Takeshita, M., Curnutte, J. T., Uhlinger, D. J., and Lambeth, J. D. (1992) J. Biol. Chem. 267, 7529-7538]. In an attempt to stabilize the activity and to investigate the nature of the complex, we have produced fusion proteins between rac and a C-terminal truncated form of p67(phox) (residues 1-210, 67N), which is a minimal active fragment. In a cell-free system, a fusion protein 67N-rac had higher activity and a 3-fold higher affinity than the individual cytosolic proteins, and 67N-Ser3-rac, which has a longer linker, showed a similar activity with the individual proteins. In contrast, rac-67N, a fusion in the opposite orientation, showed considerably lower activity. The enzyme activity reconstituted with 67N-rac showed a 10-fold higher stability and a lower K(m) for NADPH than the individual components. In the absence of p47, 67N-rac fusion protein at a high concentration showed nearly full activation, which was higher than that with the individual components. These results indicate that covalent binding between p67N and rac in the correct order produces a more stable complex than the individual components, suggesting that interactions among the subunits significantly influence the duration of the oxidase activation. On the basis of these findings, we propose a model for the topology among rac, 67N, and cytochrome b(558).
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Affiliation(s)
- K Miyano
- Department of Applied Chemistry, Faculty of Engineering, Ehime University, Matsuyama, Ehime 790-8577, Japan
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160
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Pessach I, Leto TL, Malech HL, Levy R. Essential requirement of cytosolic phospholipase A(2) for stimulation of NADPH oxidase-associated diaphorase activity in granulocyte-like cells. J Biol Chem 2001; 276:33495-503. [PMID: 11432850 DOI: 10.1074/jbc.m011417200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously established a model of cytosolic phospholipase A(2) (cPLA(2))-deficient differentiated PLB-985 cells (PLB-D cells) and demonstrated that cPLA(2)-generated arachidonic acid (AA) is essential for NADPH oxidase activation. In this study we used this model to investigate the physiological role of cPLA(2) in regulation of NADPH oxidase-associated diaphorase activity. A novel diaphorase activity assay, using 4-iodonitrotetrazolium violet as an electron acceptor, was used in permeabilized neutrophils and PLB-985 cells differentiated toward the granulocytic or monocytic phenotypes. Phorbol 12-myristate 13-acetate, guanosine 5'-3-O- (thio)triphosphate (GTP gamma S), or FMLP stimulated a similar diphenylene iodonium-sensitive diaphorase activity pattern in neutrophils and in differentiated parent PLB-985 cells. This diaphorase activity was not detected in undifferentiated cells, but developed during differentiation. Furthermore, diaphorase activity could not be stimulated in permeabilized neutrophils from X-linked CGD patients and in differentiated gp91(phox)-targeted PLB-985 cells that lacked normal expression of gp91(phox), but was restored to these cells following transduction with retrovirus encoding gp91(phox). The differentiated PLB-D cells showed no diaphorase activity when stimulated by either GTP gamma S or FMLP, and only partial activation when stimulated with phorbol 12-myristate 13-acetate. Diaphorase activity in response to either agonists was fully restored by the addition of 10 microm free AA. The permeabilized cell 4-iodonitrotetrazolium violet reduction assay offers a unique tool for the evaluation of NADPH oxidase-associated diaphorase activity in stimulated whole cells. These results establish an essential and specific physiological requirement of cPLA(2)-generated AA in activation of electron transfer through the FAD reduction center of NADPH oxidase.
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Affiliation(s)
- I Pessach
- Infectious Diseases Laboratory, Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev and Soroka Medical Center, Beer Sheva 84105, Israel
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161
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Kuncewicz T, Balakrishnan P, Snuggs MB, Kone BC. Specific association of nitric oxide synthase-2 with Rac isoforms in activated murine macrophages. Am J Physiol Renal Physiol 2001; 281:F326-36. [PMID: 11457725 DOI: 10.1152/ajprenal.2001.281.2.f326] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Nitric oxide synthase-2 (NOS2) is responsible for high-output nitric oxide production important in renal inflammation and injury. Using a yeast two-hybrid assay, we identified Rac2, a Rho GTPase member, as a NOS2-interacting protein. NOS2 and Rac2 proteins coimmunoprecipitated from activated RAW 264.7 macrophages. The two proteins colocalized in an intracellular compartment of these cells. Glutathione-S-transferase (GST) pull-down assays revealed that both Rac1 and Rac2 associated with GST-NOS2 and that the NOS2 oxygenase domain was necessary and sufficient for the interaction. [(35)S]methionine-labeled NOS2 interacted directly with GST-Rac2 in the absence of GTP, calmodulin, or NOS2 substrates or cofactors. Stable overexpression of Rac2 in RAW 264.7 cells augmented LPS-induced nitrite generation (~60%) and NOS2 activity (~45%) without measurably affecting NOS2 protein abundance and led to a redistribution of NOS2 to a high-speed Triton X-100-insoluble fraction. We conclude that Rac1 and Rac2 physically interact with NOS2 in activated macrophages and that the interaction with Rac2 correlates with a posttranslational stimulation of NOS2 activity and likely its spatial redistribution within the cell.
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Affiliation(s)
- T Kuncewicz
- Department of Internal Medicine, The University of Texas Medical School at Houston, Houston, Texas 77030, USA
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162
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Grizot S, Fieschi F, Dagher MC, Pebay-Peyroula E. The active N-terminal region of p67phox. Structure at 1.8 A resolution and biochemical characterizations of the A128V mutant implicated in chronic granulomatous disease. J Biol Chem 2001; 276:21627-31. [PMID: 11262407 DOI: 10.1074/jbc.m100893200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon activation, the NADPH oxidase from neutrophils produces superoxide anions in response to microbial infection. This enzymatic complex is activated by association of its cytosolic factors p67(phox), p47(phox), and the small G protein Rac with a membrane-associated flavocytochrome b(558). Here we report the crystal structure of the active N-terminal fragment of p67(phox) at 1.8 A resolution, as well as functional studies of p67(phox) mutants. This N-terminal region (residues 1-213) consists mainly of four TPR (tetratricopeptide repeat) motifs in which the C terminus folds back into a hydrophobic groove formed by the TPR domain. The structure is very similar to that of the inactive truncated form of p67(phox) bound to the small G protein Rac previously reported, but differs by the presence of a short C-terminal helix (residues 187-193) that might be part of the activation domain. All p67(phox) mutants responsible for Chronic Granulomatous Disease (CGD), a severe defect of NADPH oxidase function, are localized in the N-terminal region. We investigated two CGD mutations, G78E and A128V. Surprisingly, the A128V CGD mutant is able to fully activate the NADPH oxidase in vitro at 25 degrees C. However, this point mutation represents a temperature-sensitive defect in p67(phox) that explains its phenotype at physiological temperature.
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Affiliation(s)
- S Grizot
- Institut de Biologie Structurale, CEA-CNRS-UJF, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble cedex 1, France
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163
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Tisch-Idelson D, Fridkin M, Wientjes F, Aviram I. Structure-function relationship in the interaction of mastoparan analogs with neutrophil NADPH oxidase. Biochem Pharmacol 2001; 61:1063-71. [PMID: 11301039 DOI: 10.1016/s0006-2952(01)00561-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mastoparan, an amphiphilic cationic tetradecapeptide was previously shown to block activation of the NADPH oxidase in the cell-free system presumably by association with a cytosolic component/s of the enzyme. Blockade of oxidase activation was now demonstrated in the semirecombinant NADPH oxidase system. The structural basis of the inhibitory effect of MP on oxidase assembly was explored employing a variety of truncated and specifically substituted synthetic peptide analogs. The data indicated that an alpha helical fold, positive net charge, hydrophobicity and amphiphilicity were essential for the inhibitory potency and that peptide analogs below eleven residues were inactive. To identify the MP-binding oxidase subunit three different binding assays were carried out utilizing free or immobilized recombinant p47-phox, p67-phox, p40-phox and Rac1 in conjunction with immobilized MP or soluble (125)I-tyr-MP, respectively. The data implicated p67-phox as the main MP-binding component. The binding site on the p67-phox was localized to the 1-238 aminoterminal fragment of the molecule. NADPH oxidase activation supported by this fragment was inhibitable by MP. In addition, SH3 domains of p47-phox and p40-phox and the carboxyterminal SH3 domain of p67-phox exhibited a low affinity towards MP.
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Affiliation(s)
- D Tisch-Idelson
- Department of Biochemistry, Tel Aviv University, Tel Aviv, Israel
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164
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Abstract
The neutrophil is a critical effector cell in humoral and innate immunity and plays vital roles in phagocytosis and bacterial killing. Discussed here are the neutrophil components necessary for these processes and the diseases in which these components are either lacking or dysfunctional, illustrating that normal neutrophil function is vital for health.
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Affiliation(s)
- N D Burg
- Department of Medicine, New York University School of Medicine, New York, New York 10016, USA.
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165
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Grizot S, Grandvaux N, Fieschi F, Fauré J, Massenet C, Andrieu JP, Fuchs A, Vignais PV, Timmins PA, Dagher MC, Pebay-Peyroula E. Small angle neutron scattering and gel filtration analyses of neutrophil NADPH oxidase cytosolic factors highlight the role of the C-terminal end of p47phox in the association with p40phox. Biochemistry 2001; 40:3127-33. [PMID: 11258927 DOI: 10.1021/bi0028439] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The NADPH oxidase of phagocytic cells is regulated by the cytosolic factors p47(phox), p67(phox), and p40(phox) as well as by the Rac1-Rho-GDI heterodimer. The regulation is a consequence of protein-protein interactions involving a variety of protein domains that are well characterized in signal transduction. We have studied the behavior of the NADPH oxidase cytosolic factors in solution using small angle neutron scattering and gel filtration. p47(phox), two truncated forms of p47(phox), namely, p47(phox) without its C-terminal end (residues 1-358) and p47(phox) without its N-terminal end (residues 147-390), and p40(phox) were found to be monomeric in solution. The dimeric form of p67(phox) previously observed by gel filtration experiments was confirmed. Our small angle neutron scattering experiments show that p40(phox) binds to the full-length p47(phox) in solution in the absence of phosphorylation. We demonstrated that the C-terminal end of p47(phox) is essential in this interaction. From the comparison of the presence or absence of interaction with various truncated forms of the proteins, we confirmed that the SH3 domain of p40(phox) interacts with the C-terminal proline rich region of p47(phox). The radii of gyration observed for p47(phox) and the truncated forms of p47(phox) (without the C-terminal end or without the N-terminal end) show that all these molecules are elongated and that the N-terminal end of p47(phox) is globular. These results suggest that the role of amphiphiles such as SDS or arachidonic acid or of p47(phox) phosphorylation in the elicitation of NADPH oxidase activation could be to disrupt the p40(phox)-p47(phox) complex rather than to break an intramolecular interaction in p47(phox).
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Affiliation(s)
- S Grizot
- Institut de Biologie Structurale, CEA-CNRS-UJF, UMR 5075, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France
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166
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Noda Y, Takeya R, Ohno S, Naito S, Ito T, Sumimoto H. Human homologues of the Caenorhabditis elegans cell polarity protein PAR6 as an adaptor that links the small GTPases Rac and Cdc42 to atypical protein kinase C. Genes Cells 2001; 6:107-19. [PMID: 11260256 DOI: 10.1046/j.1365-2443.2001.00404.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Asymmetric cell division in the Caenorhabditis elegans embryos requires products of par (partitioning defective) genes 1-6 and atypical protein kinase C (aPKC), whereas Cdc42 and Rac, members of the Rho family GTPases, play an essential role in cell polarity establishment in yeast and mammalian cells. However, little is known about a link between PAR proteins and the GTPases in cell polarization. RESULTS Here we have cloned cDNAs for three human homologues of PAR6, designated PAR6alpha, beta and gamma, comprising 345, 372 and 376 amino acids, respectively. The PAR6 proteins harbour a PDZ domain and a CRIB-like motif, and directly interact with GTP-bound Rac and Cdc42 via this motif and with the aPKC isoforms PKCiota/lambda and PKCzeta via the N-terminal head-to-head association. These interactions are not mutually exclusive, thereby allowing the PAR6 proteins to form a ternary complex with the GTPases and aPKC, both in vitro and in vivo. When PAR6 and aPKC are expressed with a constitutively active form of Rac in HeLa or COS-7 cells, these proteins co-localize to membrane ruffles, which are known to occur at the leading edge of polarized cells during cell movement. CONCLUSION Human PAR6 homologues most likely play an important role in the cell polarization of mammalian cells, by functioning as an adaptor protein that links activated Rac and Cdc42 to aPKC signalling.
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Affiliation(s)
- Y Noda
- Department of Molecular and Structural Biology, Kyushu University Graduate School of Medical Science, Fukuoka 812-8582, Japan
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167
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Kim C, Dinauer MC. Rac2 is an essential regulator of neutrophil nicotinamide adenine dinucleotide phosphate oxidase activation in response to specific signaling pathways. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 166:1223-32. [PMID: 11145705 DOI: 10.4049/jimmunol.166.2.1223] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Rac2 is a hematopoietic-specific Rho family GTPase implicated as an important constituent of the NADPH oxidase complex and shares 92% amino acid identity with the ubiquitously expressed Rac1. In bone marrow (BM) neutrophils isolated from rac2(-/-) mice generated by gene targeting, we previously reported that PMA-induced superoxide production was reduced by about 4-fold, which was partially corrected in TNF-alpha-primed BM neutrophils and in peritoneal exudate neutrophils. We investigated receptor-mediated activation of the NADPH oxidase in the current study, finding that superoxide production in rac2(-/-) BM and peritoneal exudate neutrophils was normal in response to opsonized zymosan, reduced to 22% of wild type in response to IgG-coated SRBC, and almost absent in response to fMLP. In wild-type murine BM neutrophils, phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and Akt was induced by PMA or fMLP, which was decreased in rac2(-/-) neutrophils for ERK1/2 and p38. Activation of p38 by either opsonized zymosan or IgG-coated SRBC was similar in wild-type and rac2(-/-) cells. Inhibition of ERK1/2 or p38 activation using either PD98059 or SB203580, respectively, had only a modest effect on fMLP-elicited superoxide production and no effect on the PMA-induced response. These data provide genetic evidence supporting an important role for Rac2 in regulating neutrophil NADPH oxidase activation downstream of chemoattractant and Fcgamma receptors. The effect of Rac2 deficiency on superoxide production is probably exerted through multiple pathways, including those independent of mitogen-activated protein kinase activation.
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Affiliation(s)
- C Kim
- The Herman B Wells Center for Pediatric Research, Department of Pediatrics, The James Whitcomb Riley Hospital for Children, Indiana University Medical Center, Indianapolis, IN 46202, USA
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168
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Shiose A, Kuroda J, Tsuruya K, Hirai M, Hirakata H, Naito S, Hattori M, Sakaki Y, Sumimoto H. A novel superoxide-producing NAD(P)H oxidase in kidney. J Biol Chem 2001; 276:1417-23. [PMID: 11032835 DOI: 10.1074/jbc.m007597200] [Citation(s) in RCA: 395] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During phagocytosis, gp91(phox), the catalytic subunit of the phagocyte NADPH oxidase, becomes activated to produce superoxide, a precursor of microbicidal oxidants. Currently increasing evidence suggests that nonphagocytic cells contain similar superoxide-producing oxidases, which are proposed to play crucial roles in various events such as cell proliferation and oxygen sensing for erythropoiesis. Here we describe the cloning of human cDNA that encodes a novel NAD(P)H oxidase, designated NOX4. The NOX4 protein of 578 amino acids exhibits 39% identity to gp91(phox) with special conservation in membrane-spanning regions and binding sites for heme, FAD, and NAD(P)H, indicative of its function as a superoxide-producing NAD(P)H oxidase. The membrane fraction of kidney-derived human embryonic kidney (HEK) 293 cells, expressing NOX4, exhibits NADH- and NADPH-dependent superoxide-producing activities, both of which are inhibited by diphenylene iodonium, an agent known to block oxygen sensing, and decreased in cells expressing antisense NOX4 mRNA. The human NOX4 gene, comprising 18 exons, is located on chromosome 11q14.2-q21, and its expression is almost exclusively restricted to adult and fetal kidneys. In human renal cortex, high amounts of the NOX4 protein are present in distal tubular cells, which reside near erythropoietin-producing cells. In addition, overexpression of NOX4 in cultured cells leads to increased superoxide production and decreased rate of growth. The present findings thus suggest that the novel NAD(P)H oxidase NOX4 may serve as an oxygen sensor and/or a regulator of cell growth in kidney.
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Affiliation(s)
- A Shiose
- Department of Molecular and Structural Biology, Kyushu University Graduate School of Medical Science, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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169
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De Vries L, Fischer T, Tronchère H, Brothers GM, Strockbine B, Siderovski DP, Farquhar MG. Activator of G protein signaling 3 is a guanine dissociation inhibitor for Galpha i subunits. Proc Natl Acad Sci U S A 2000; 97:14364-9. [PMID: 11121039 PMCID: PMC18924 DOI: 10.1073/pnas.97.26.14364] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activator of G protein signaling 3 (AGS3) is a newly identified protein shown to act at the level of the G protein itself. AGS3 belongs to the GoLoco family of proteins, sharing the 19-aa GoLoco motif that is a Galpha(i/o) binding motif. AGS3 interacts only with members of the Galpha(i/o) subfamily. By surface plasmon resonance, we found that AGS3 binds exclusively to the GDP-bound form of Galpha(i3). In GTPgammaS binding assays, AGS3 behaves as a guanine dissociation inhibitor (GDI), inhibiting the rate of exchange of GDP for GTP by Galpha(i3). AGS3 interacts with both Galpha(i3) and Galpha(o) subunits, but has GDI activity only on Galpha(i3), not on Galpha(o). The fourth GoLoco motif of AGS3 is a major contributor to this activity. AGS3 stabilizes Galpha(i3) in its GDP-bound form, as it inhibits the increase in tryptophan fluorescence of the Galpha(i3)-GDP subunit stimulated by AlF(4)(-). AGS3 is widely expressed as it is detected by immunoblotting in brain, testis, liver, kidney, heart, pancreas, and in PC-12 cells. Several different sizes of the protein are detected. By Northern blotting, AGS3 shows 2.3-kb and 3.5-kb mRNAs in heart and brain, respectively, suggesting tissue-specific alternative splicing. Taken together, our results demonstrate that AGS3 is a GDI. To the best of our knowledge, no other GDI has been described for heterotrimeric G proteins. Inhibition of the Galpha subunit and stimulation of heterotrimeric G protein signaling, presumably by stimulating Gbetagamma, extend the possibilities for modulating signal transduction through heterotrimeric G proteins.
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Affiliation(s)
- L De Vries
- Departments of Cellular and Molecular Medicine and Pathology, University of California at San Diego, La Jolla, CA 92093-0651, USA
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170
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Poetsch M, Dittberner T, Cowell JK, Woenckhaus C. TTC4, a novel candidate tumor suppressor gene at 1p31 is often mutated in malignant melanoma of the skin. Oncogene 2000; 19:5817-20. [PMID: 11126369 DOI: 10.1038/sj.onc.1203961] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A novel candidate tumor suppressor gene, TTC4, on chromosome 1p31 has been described recently. Since aberrations in this region have been detected in malignant melanoma, we investigated DNA of paraffin-embedded sections from 16 typical naevi, 19 atypical naevi, 32 primary melanomas (15 superficial spreading melanomas, 17 nodular melanomas) and 25 metastases and DNA from four melanoma cell lines by PCR and direct sequencing analysis for mutations in all exons of TTC4. Tumors comprised a wide range of thickness (Breslow index) and Clark levels. No mutations could be detected in typical or atypical naevi, but we found seven different point mutations in the tumor samples, six of them causing an amino acid change. Ten melanoma samples belonging to nine patients showed one or more of these mutations. In detail, in six of 25 metastases, in two of 17 nodular melanomas and in two of 15 superficial spreading melanomas point mutations could be detected. In two cell lines, a loss of a whole exon could be demonstrated and in one cell line we found a point mutation. In addition, three polymorphisms were found. Our findings indicate that TTC4 may participate in the pathogenesis of malignant melanomas of the skin.
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Affiliation(s)
- M Poetsch
- Institute of Forensic Medicine, University of Greifswald, Germany
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171
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Lapouge K, Smith SJ, Walker PA, Gamblin SJ, Smerdon SJ, Rittinger K. Structure of the TPR domain of p67phox in complex with Rac.GTP. Mol Cell 2000; 6:899-907. [PMID: 11090627 DOI: 10.1016/s1097-2765(05)00091-2] [Citation(s) in RCA: 236] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
p67phox is an essential part of the NADPH oxidase, a multiprotein enzyme complex that produces superoxide ions in response to microbial infection. Binding of the small GTPase Rac to p67phox is a key step in the assembly of the active enzyme complex. The structure of Rac.GTP bound to the N-terminal TPR (tetratricopeptide repeat) domain of p67phox reveals a novel mode of Rho family/effector interaction and explains the basis of GTPase specificity. Complex formation is largely mediated by an insertion between two TPR motifs, suggesting an unsuspected versatility of TPR domains in target recognition and in their more general role as scaffolds for the assembly of multiprotein complexes.
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Affiliation(s)
- K Lapouge
- Division of Protein Structure, National Institute for Medical Research, London, United Kingdom
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172
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Paclet MH, Coleman AW, Vergnaud S, Morel F. P67-phox-mediated NADPH oxidase assembly: imaging of cytochrome b558 liposomes by atomic force microscopy. Biochemistry 2000; 39:9302-10. [PMID: 10924123 DOI: 10.1021/bi000483j] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
NADPH oxidase activity depends on the assembly of the cytosolic activating factors, p67-phox, p47-phox, p40-phox, and Rac with cytochrome b(558). The transition from an inactive to an active oxidase complex induces the transfer of electrons from NADPH to oxygen through cytochrome b(558). The assembly of oxidase complex was studied in vitro after reconstitution in a heterologous cell-free assay by using true noncontact mode atomic force microscopy. Cytochrome b(558) was purified from neutrophils and Epstein-Barr virus-immortalized B lymphocytes and incorporated into liposomes. The effect of protein glycosylation on liposome size and oxidase activity was investigated. The liposomes containing the native hemoprotein purified from neutrophils had a diameter of 146 nm, whereas after deglycosylation, the diameter was reduced to 68 nm, although oxidase activity was similar in both cases. Native cytochrome b(558) was used after purification in reconstitution experiments to investigate the topography of NADPH oxidase once it was assembled. For the first time, atomic force microscopy illustrated conformational changes of cytochrome b(558) during the transition from the inactive to the active state of oxidase; height measurements allow the determination of a size of 4 nm for the assembled complex. In the processes that were studied, p67-phox displayed a critical function; it was shown to be involved in both assembly and activation of oxidase complex while p47-phox proceeded as a positive effector and increased the affinity of p67-phox with cytochrome b(558), and p40-phox stabilizes the resting state. The results suggest that although an oligomeric structure of oxidase machinery has not been demonstrated, allosteric regulation mechanisms may be proposed.
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Affiliation(s)
- M H Paclet
- GREPI EA 2938 MENRT laboratoire Enzymologie, CHU Grenoble BP 217, 38043 Grenoble Cedex, France
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173
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Shiose A, Sumimoto H. Arachidonic acid and phosphorylation synergistically induce a conformational change of p47phox to activate the phagocyte NADPH oxidase. J Biol Chem 2000; 275:13793-801. [PMID: 10788501 DOI: 10.1074/jbc.275.18.13793] [Citation(s) in RCA: 185] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The superoxide-producing phagocyte NADPH oxidase can be activated by arachidonic acid (AA) or by phosphorylation of p47(phox) under cell-free conditions. The molecular mechanism underlying the activation, however, has remained largely unknown. Here we demonstrate that AA, at high concentrations (50-100 micrometer), induces direct interaction between the oxidase factors p47(phox) and p22(phox) in parallel with superoxide production. The interaction, being required for the oxidase activation, is mediated via the Src homology 3 (SH3) domains of p47(phox) (p47-(SH3)(2)), which are intramolecularly masked in a resting state. We also show that AA disrupts complexation of p47-(SH3)(2) with its intramolecular target fragment (amino acids 286-340) without affecting association of p47-(SH3)(2) with p22(phox), indicating that the disruption plays a crucial role in the induced interaction with p22(phox). Phosphorylation of p47(phox) by protein kinase C partially replaces the effects of AA; treatment of the SH3 target fragment with PKC in vitro results in a completely impaired interaction with p47-(SH3)(2), and the same treatment of the full-length p47(phox) leads to both interaction with p22(phox) and oxidase activation without AA, but to a lesser extent. Furthermore, phosphorylated p47(phox) effectively binds to p22(phox) and activates the oxidase in the presence of AA at low concentrations (1-5 micrometer), where an unphosphorylated protein only slightly supports superoxide production. Thus AA, at high concentrations, fully induces the interaction of p47(phox) with p22(phox) by itself, whereas, at low concentrations, AA synergizes with phosphorylation of p47(phox) to facilitate the interaction, thereby activating the NADPH oxidase.
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Affiliation(s)
- A Shiose
- Department of Molecular and Structural Biology, Kyushu University Graduate School of Medical Science, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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174
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Gounalaki N, Tzamarias D, Vlassi M. Identification of residues in the TPR domain of Ssn6 responsible for interaction with the Tup1 protein. FEBS Lett 2000; 473:37-41. [PMID: 10802055 DOI: 10.1016/s0014-5793(00)01480-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ssn6, a yeast protein that comprises 10 tandem tetratricopeptide repeat (TPR) motifs, associates with Tup1 repressor protein and acts as a transcriptional corepressor. In this report we identify point mutations in the TPR1 of Ssn6 that disrupt Tup1 interaction. Furthermore, we construct a 3D model of the TPR domain of Ssn6, which is responsible for Tup1 binding, based on the known structure of protein phosphatase 5. According to this model all selected mutations reduce the ability of Ssn6 to interact with Tup1 by affecting the structural integrity of TPR1 and/or the correct spatial arrangement of TPR1 relative to TPR2 and TPR3.
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Affiliation(s)
- N Gounalaki
- Institute of Molecular Biology and Biotechnology-Foundation of Research and Technology, Vassilika Vouton, P.O. Box 711 10, Heraklion, Crete, Greece
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175
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Dang PM, Johnson JL, Babior BM. Binding of nicotinamide adenine dinucleotide phosphate to the tetratricopeptide repeat domains at the N-terminus of p67PHOX, a subunit of the leukocyte nicotinamide adenine dinucleotide phosphate oxidase. Biochemistry 2000; 39:3069-75. [PMID: 10715128 DOI: 10.1021/bi9919807] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nicotinamide adenine dinucleotide phosphate (NADPH) binding site of the NADPH oxidase complex is believed to be located on the beta, subunit of cytochrome b558. However, our previous studies showed that p67PHOX also contains an NADPH binding site that is essential for normal oxidase activity and that p67PHOX is able to mediate a slow electron transfer from a reduced pyridine nucleotide to an artificial electron acceptor. Using both affinity labeling and fluorescence quenching, we have obtained further evidence that p67PHOX is able to bind NADPH. We have used a number of truncated forms of p67PHOX, including p67PHOX(1-243), p67PHOX(1-210), p67PHOX(1-199), and p67PHOX(244-526) (where the numbers represent the initial and final amino acids in the truncated p67PHOX) in order to localize the binding site. We found that NADPH could bind to p67PHOX(1-243), p67PHOX(1-210), and p67PHOX(1-199) but not to p67PHOX(244-526). The p67PHOX(1-199) fragment consists largely of four tetratricopeptide (TPR) domains. We showed further that Rac2-GTP gamma S and to a lesser extent Rac2-GDP beta S could modulate the binding of NADPH to p67PHOX.
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Affiliation(s)
- P M Dang
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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176
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Abstract
Abstract
Recent advances in our understanding of the molecular basis of inherited neutrophil disorders and complementary studies in transgenic mouse models have provided new insights into the normal mechanisms regulating myelopoiesis and the functional responses of mature neutrophils. Neutrophil specific granule deficiency is a rare disorder of neutrophil function characterized by a lack of neutrophil secondary granule proteins and associated with recurrent bacterial infections. The CCAAT/enhancer binding protein (C/EBP) ϵ, a leucine zipper transcription factor expressed primarily in myeloid cells, and C/EBPϵ-deficient mice generated by gene targeting lack specific granules and have impaired host defense are discussed by Dr. Lekstrom-Himes in Section I. The similarity between these phenotypes led to the identification of a loss of function mutation in the C/EBPϵ gene in a subset of patients with specific granule deficiency. Dr. Dale reviews the clinical features and management of congenital neutropenia and cyclic hematopoiesis in Section II. Inherited mutations in the neutrophil elastase gene have recently been identified in both disorders. Specific mutations identified in cyclic and congenital neutropenia are described along with possible mechanisms for regulation of hematopoiesis by neutrophil elastase. In Section III, Dr. Dinauer reviews the molecular genetics of chronic granulomatous disease and studies in knockout mouse models. This work has revealed important features of the regulation of the respiratory burst oxidase and its role in host defense and inflammation. Results from preclinical studies and phase 1 clinical trials for gene therapy for CGD are summarized, in addition to alternative approaches using allogeneic bone marrow transplantation with nonmyeloablative conditioning.
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Abstract
Recent advances in our understanding of the molecular basis of inherited neutrophil disorders and complementary studies in transgenic mouse models have provided new insights into the normal mechanisms regulating myelopoiesis and the functional responses of mature neutrophils. Neutrophil specific granule deficiency is a rare disorder of neutrophil function characterized by a lack of neutrophil secondary granule proteins and associated with recurrent bacterial infections. The CCAAT/enhancer binding protein (C/EBP) ϵ, a leucine zipper transcription factor expressed primarily in myeloid cells, and C/EBPϵ-deficient mice generated by gene targeting lack specific granules and have impaired host defense are discussed by Dr. Lekstrom-Himes in Section I. The similarity between these phenotypes led to the identification of a loss of function mutation in the C/EBPϵ gene in a subset of patients with specific granule deficiency. Dr. Dale reviews the clinical features and management of congenital neutropenia and cyclic hematopoiesis in Section II. Inherited mutations in the neutrophil elastase gene have recently been identified in both disorders. Specific mutations identified in cyclic and congenital neutropenia are described along with possible mechanisms for regulation of hematopoiesis by neutrophil elastase. In Section III, Dr. Dinauer reviews the molecular genetics of chronic granulomatous disease and studies in knockout mouse models. This work has revealed important features of the regulation of the respiratory burst oxidase and its role in host defense and inflammation. Results from preclinical studies and phase 1 clinical trials for gene therapy for CGD are summarized, in addition to alternative approaches using allogeneic bone marrow transplantation with nonmyeloablative conditioning.
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