Recognition and removal by phagocytes is the culmination of the death process for most apoptotic cells. Loss of phospholipid asymmetry leads to exposure of phosphatidylserine (PS) on the apoptotic cell surface; the polar head group of this phospholipid is recognized in a stereospecific manner, suggesting the existence of a PS-specific receptor. Using phage display and biopanning, we have cloned a novel gene we believe to be an authentic PS receptor; the mammalian protein has homologues in Drosophila and in C. elegans, the function of which are unknown. The protein is expressed on the surface of macrophages, fibroblasts, and epithelial cells, all of which can engulf apoptotic cells. Monoclonal antibodies against this receptor inhibit uptake of apoptotic cells only by those phagocytes which are inhibited by PS liposomes. Furthermore, binding of the antibodies to the cell surface is inhibited by PS, but not by other anionic phospholipids. Transfection of the gene into Jurkat cells, which do not express the gene normally, induced the ability to bind to and take up apoptotic cells: this was not seen in Jurkats transfected with empty vector. Using biochemical, molecular, and genetic methods (including RNAi and transformation rescue in C. elegans), the investigators hope to define the function of this receptor and its ligand specificity. The investigators hypothesize that PS recognition has been preserved throughout phylogeny as an effective mechanism mediating the removal of apoantibodies.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM060449-04
Application #
6627273
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Chin, Jean
Project Start
2000-01-01
Project End
2004-12-31
Budget Start
2003-01-01
Budget End
2003-12-31
Support Year
4
Fiscal Year
2003
Total Cost
$210,080
Indirect Cost
Name
National Jewish Health
Department
Type
DUNS #
076443019
City
Denver
State
CO
Country
United States
Zip Code
80206
Monks, J; Rosner, D; Geske, F Jon et al. (2005) Epithelial cells as phagocytes: apoptotic epithelial cells are engulfed by mammary alveolar epithelial cells and repress inflammatory mediator release. Cell Death Differ 12:107-14
Hoffmann, Peter R; Kench, Jennifer A; Vondracek, Andrea et al. (2005) Interaction between phosphatidylserine and the phosphatidylserine receptor inhibits immune responses in vivo. J Immunol 174:1393-404
Kittle, Lori A; Sawyer, Richard T; Fadok, Valerie A et al. (2002) Beryllium induces apoptosis in human lung macrophages. Sarcoidosis Vasc Diffuse Lung Dis 19:101-13
Huynh, Mai-Lan N; Fadok, Valerie A; Henson, Peter M (2002) Phosphatidylserine-dependent ingestion of apoptotic cells promotes TGF-beta1 secretion and the resolution of inflammation. J Clin Invest 109:41-50
Monks, Jenifer; Geske, F Jon; Lehman, Lisa et al. (2002) Do inflammatory cells participate in mammary gland involution? J Mammary Gland Biol Neoplasia 7:163-76
Hoffmann, P R; deCathelineau, A M; Ogden, C A et al. (2001) Phosphatidylserine (PS) induces PS receptor-mediated macropinocytosis and promotes clearance of apoptotic cells. J Cell Biol 155:649-59
Fadok, V A; Bratton, D L; Guthrie, L et al. (2001) Differential effects of apoptotic versus lysed cells on macrophage production of cytokines: role of proteases. J Immunol 166:6847-54