Oxygen-dependent proinflammatory functions of polymorphonuclear leukocytes (PMNs) reflect synergy between granule contents and reactive oxygen species. Myeloperoxidase (MPO), a heme protein in the azurophilic granules, catalyzes the generation of HOCI in the presence of H2O2. The NADPH-dependent oxidase contains flavocytochrome b558, a heterodimeric membrane component that like MPO is a hemeprotein. Since these two hemeproteins are essential for optimal PMN activity, the biosynthesis of each in the endoplasmic reticulum (ER) is finely controlled to optimize correct folding and acquisition of heme. The applicants have identified two ER resident proteins, calreticulin (CRT) and calnexin (CLN), as participants in the biosynthesis of normal MPO and in the retrieval and degradation of mutated MPO. During the past year they have also initiated studies to characterize features of normal flavocytochrome b558 biosynthesis.Currently unknown are the means by which heme is inserted into apoproteins synthesized in the ER or, in the case of flavocytochrome b558, the determinants of subunit association. Information is also limited on the role of molecular chaperones in monitoring quality control during myeloid protein synthesis or on the precise peptide motifs recognized by CRT and CLN that target a given protein as """"""""unfolded."""""""" Using MPO and flavocytochrome b558 as representative myeloid proteins, the applicants aim to test the hypotheses: (a) that heme acquisition and/or heterodimer formation are events essential for normal biosynthetic maturation of flavocytochrome b558; (b) that heme acquisition by apoforms is facilitated by ER-resident molecular chaperones; and (c) that CRT and CLN recognize specific peptide motifs in MPO precursors. The applicants will test these hypotheses by pursuing three specific aims: (1) to characterize critical steps in flavocytochrome b558 biosynthesis, specifically heme acquisition and heterodimer formation; (2) to define the relative roles of CRT/CLN in heme acquisition and ER """"""""quality control"""""""" during MPO biosynthesis; and (3) to determine the relative importance of heme acquisition and heterodimer formation to the biogenesis of other members of the NOX protein family. The applicants believe that these will define principles that apply not only to these specific myeloid proteins but to proteins in general that acquire heme in the ER.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
2R01HL053592-05A1
Application #
6547241
Study Section
Hematology Subcommittee 2 (HEM)
Program Officer
Thomas, John
Project Start
1996-12-11
Project End
2006-06-30
Budget Start
2002-07-01
Budget End
2003-06-30
Support Year
5
Fiscal Year
2002
Total Cost
$252,000
Indirect Cost
Name
University of Iowa
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
041294109
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Nauseef, William M (2008) Biological roles for the NOX family NADPH oxidases. J Biol Chem 283:16961-5
Nauseef, William M (2008) Nox enzymes in immune cells. Semin Immunopathol 30:195-208
Nakano, Yoko; Banfi, Botond; Jesaitis, Algirdas J et al. (2007) Critical roles for p22phox in the structural maturation and subcellular targeting of Nox3. Biochem J 403:97-108
Goedken, Melissa; McCormick, Sally; Leidal, Kevin G et al. (2007) Impact of two novel mutations on the structure and function of human myeloperoxidase. J Biol Chem 282:27994-8003
Nauseef, William M (2007) How human neutrophils kill and degrade microbes: an integrated view. Immunol Rev 219:88-102
Zhu, Yanmin; Marchal, Christophe C; Casbon, Amy-Jo et al. (2006) Deletion mutagenesis of p22phox subunit of flavocytochrome b558: identification of regions critical for gp91phox maturation and NADPH oxidase activity. J Biol Chem 281:30336-46
Hansson, Markus; Olsson, Inge; Nauseef, William M (2006) Biosynthesis, processing, and sorting of human myeloperoxidase. Arch Biochem Biophys 445:214-24
Baniulis, Danas; Nakano, Yoko; Nauseef, William M et al. (2005) Evaluation of two anti-gp91phox antibodies as immunoprobes for Nox family proteins: mAb 54.1 recognizes recombinant full-length Nox2, Nox3 and the C-terminal domains of Nox1-4 and cross-reacts with GRP 58. Biochim Biophys Acta 1752:186-96
Nauseef, William M (2004) Assembly of the phagocyte NADPH oxidase. Histochem Cell Biol 122:277-91
Bulow, E; Nauseef, W M; Goedken, M et al. (2002) Sorting for storage in myeloid cells of nonmyeloid proteins and chimeras with the propeptide of myeloperoxidase precursor. J Leukoc Biol 71:279-88

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