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Infection and Immunity, September 1999, p. 4693-4699, Vol. 67, No. 9
Department of Cell Biology, Duke University
Medical Center, Durham, North Carolina 27710
Received 3 February 1999/Returned for modification 15 March
1999/Accepted 1 July 1999
Surfactant protein A (SP-A), a pulmonary member of the collectin
family of proteins, facilitates the rapid clearance of pathogens by
upregulating immune cell functions in the lungs. SP-A binds to bacteria
and targets them for rapid phagocytosis by alveolar macrophages, but
the mechanism by which this stimulation occurs is not clear. To
characterize the intracellular events that may be involved, we examined
the roles of protein phosphorylation and cytoskeletal polymerization in
SP-A-stimulated phagocytosis. In rat alveolar macrophages, SP-A
stimulated rapid tyrosine phosphorylation of specific proteins in a
dose- and time-dependent manner. The pattern of proteins that were
phosphorylated in response to SP-A, as resolved by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis, was similar to that
observed for immunoglobulin G (IgG)-stimulated macrophages. Both SP-A
and IgG stimulated increases in phagocytosis of Streptococcus
pneumoniae above levels in the absence of added protein by 394% ± 81% and 200% ± 25%, respectively. Phagocytosis in both cases was
dependent on tyrosine kinases, protein kinase C, and actin
polymerization but not on microtubule activity. These studies show that
SP-A utilizes pathways similar to those used by IgG to increase
macrophage phagocytosis of bacteria.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Regulation of Protein Phosphorylation and Pathogen
Phagocytosis by Surfactant Protein A
*
Corresponding author. Mailing address: Box 3709, Department of Cell Biology, Duke University Medical Center, Durham, NC
27710. Phone: (919) 684-8040. Fax: (919) 684-8106. E-mail:
J.Wright{at}cellbio.duke.edu.
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