This application will test the hypothesis that surfactant protein-A (SP-A), a pulmonary collectin, plays a critical role in protecting the lung from bacterial infection by modulating surface receptors on alveolar macrophages. Preliminary data presented in this application provides a clear relationship between SP-A and complement receptor type 3 (CR3) providing a strong inference that SP-A effects are mediated through CR3. We propose that SP-A serves complex regulatory roles in the lung, binding to cell surface receptors present on alveolar macrophages influencing binding, uptake, and killing of microorganisms. CR3 is an important phagocyte receptor for recognition of microbial pathogens and is responsible for mediating phagocytosis, degranulation, and respiratory bursts by phagocytic cells. CR3 mediated phagocytosis is important in clearance of group B streptococcus (GBS) and Haemophilus influenza, both important pathogens in childhood disease. This application will utilize models in which the synthesis of SP-A is altered genetically, using SP-A-/- and SP-A+/+ mice to determine if CR3 expression on alveolar macrophages is altered in the absence of SP-A. This application will test the central hypothesis that SP-A enhances phagocytosis and activates alveolar macrophages by modulating surface receptors mediating these events.
Specific Aim 1 will test the hypothesis that SP-A regulates expression of CR3 on alveolar macrophages by mobilizing intracellular CR3 pools.
Specific Aim 2 will test the hypothesis that SP-A binds to CR3 on alveolar macrophages and will determine the specific SP-A domain that enhances CR3 expression.
Specific Aim 3 will test the hypothesis that SP-A opsonized GBS or H. influenza activate CR3 to enhance macrophage phagocytosis and oxygen radical production. Signaling pathways important in SP-A enhanced CR3 mediated phagocytosis will be studied in vitro using CR3 transfected cells and in vivo with alveolar macrophages from SP-A-/-, CR3-/-, SP-A-/-CR3-/- and wild type mice. These studies will help clarify the role of SP-A in innate defense of the lung and provide the basis for future therapies to maintain endogenous or supply exogenous SP-A to prevent morbidity from bacterial infection. ? ?

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL071522-04
Application #
7122068
Study Section
Lung Biology and Pathology Study Section (LBPA)
Program Officer
Denholm, Elizabeth M
Project Start
2003-07-01
Project End
2008-06-30
Budget Start
2006-07-01
Budget End
2007-06-30
Support Year
4
Fiscal Year
2006
Total Cost
$355,202
Indirect Cost
Name
University of Florida
Department
Pediatrics
Type
Schools of Medicine
DUNS #
969663814
City
Gainesville
State
FL
Country
United States
Zip Code
32611
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Gil, Malgorzata; McCormack, Francis X; Levine, Ann Marie (2009) Surfactant protein A modulates cell surface expression of CR3 on alveolar macrophages and enhances CR3-mediated phagocytosis. J Biol Chem 284:7495-504
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Senft, Albert P; Korfhagen, Thomas R; Whitsett, Jeffrey A et al. (2005) Surfactant protein-D regulates soluble CD14 through matrix metalloproteinase-12. J Immunol 174:4953-9