title: Serum-derived protein S binds to phosphatidylserine and stimulates the phagocytosis of apoptotic cells.
abstract: Rapid phagocytosis of apoptotic cells is thought to limit the development of inflammation and autoimmune disease. Serum enhances macrophage phagocytosis of apoptotic cells. Here we identified protein S as the factor responsible for serum-stimulated phagocytosis of apoptotic cells. Protein S is best known for its anti-thrombotic activity, serving as a cofactor for protein C. Purified protein S was equivalent to serum in its ability to stimulate macrophage phagocytosis of apoptotic lymphoma cells, and immunodepletion of protein S eliminated the prophagocytic activity of serum. Protein S acted by binding to phosphatidylserine expressed on the apoptotic cell surface. Protein S is thus a multifunctional protein that can facilitate clearance of early apoptotic cells in addition to regulating blood coagulation.
authors.affiliation: Laboratory of Biochemistry, Division of Therapeutic Proteins, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
authors.forename: Howard A
authors.initials: HA
authors.lastname: Anderson
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Maylock
authors.forename: Joy A
authors.initials: JA
authors.lastname: Williams
authors.forename: Cloud P
authors.initials: CP
authors.lastname: Paweletz
authors.forename: Hongjun
authors.initials: H
authors.lastname: Shu
authors.forename: Emily
authors.initials: E
authors.lastname: Shacter
mesh_terms: D017209:Apoptosis / Q000276:immunology*; D006801:Humans; D008264:Macrophages / Q000276:immunology; D010587:Phagocytosis / Q000276:immunology*; D010718:Phosphatidylserines / Q000097:blood*; D011485:Protein Binding; D017293:Protein S / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D010718:Phosphatidylserines; D017293:Protein S