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Phosphatidylserine (PS) induces PS receptor-mediated macropinocytosis and promotes clearance of apoptotic cells.

Hoffmann PR, deCathelineau AM, Ogden CA, Leverrier Y, Bratton DL, Daleke DL, Ridley AJ, Fadok VA, Henson PM - J. Cell Biol. (2001)

Bottom Line: Our results suggest that regardless of the receptors engaged on the phagocyte, ingestion does not occur in the absence of phosphatidylserine (PS).Further, recognition of PS was found to be dependent on the presence of the PS receptor (PSR).We propose that the phagocytosis of apoptotic cells requires two events: tethering followed by PS-stimulated, PSR-mediated macropinocytosis.

View Article: PubMed Central - PubMed

Affiliation: Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA.

ABSTRACT
Efficient phagocytosis of apoptotic cells is important for normal tissue development, homeostasis, and the resolution of inflammation. Although many receptors have been implicated in the clearance of apoptotic cells, the roles of these receptors in the engulfment process have not been well defined. We developed a novel system to distinguish between receptors involved in tethering of apoptotic cells versus those inducing their uptake. Our results suggest that regardless of the receptors engaged on the phagocyte, ingestion does not occur in the absence of phosphatidylserine (PS). Further, recognition of PS was found to be dependent on the presence of the PS receptor (PSR). Both PS and anti-PSR antibodies stimulated membrane ruffling, vesicle formation, and "bystander" uptake of cells bound to the surface of the phagocyte. We propose that the phagocytosis of apoptotic cells requires two events: tethering followed by PS-stimulated, PSR-mediated macropinocytosis.

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PS- and PSR-mediated uptake of apoptotic cells occurs by a process akin to macropinocytosis. (A) To separately examine the tethering and engulfment events, Ebab were first allowed to tether to MHC-I on the phagocyte surface for 15 min, followed by stimulation with various forms of PS, anti-PSR antibody, or EGF (positive control) for 45 min. Ebab–anti-MHC-I were engulfed by fibroblasts when stimulated with EGF, anti-PSR, or POP-L-S, but not when stimulated with POP-D-S stereoisomer or PC. Results represent mean ± SEM from three experiments. (B) Amiloride, a specific inhibitor of macropinocytosis, inhibited the engulfment of apoptotic Jurkat T cells by NIH 3T3 fibroblasts at concentrations as low as 0.3 mM. Results represent mean ± SEM from three experiments.
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fig5: PS- and PSR-mediated uptake of apoptotic cells occurs by a process akin to macropinocytosis. (A) To separately examine the tethering and engulfment events, Ebab were first allowed to tether to MHC-I on the phagocyte surface for 15 min, followed by stimulation with various forms of PS, anti-PSR antibody, or EGF (positive control) for 45 min. Ebab–anti-MHC-I were engulfed by fibroblasts when stimulated with EGF, anti-PSR, or POP-L-S, but not when stimulated with POP-D-S stereoisomer or PC. Results represent mean ± SEM from three experiments. (B) Amiloride, a specific inhibitor of macropinocytosis, inhibited the engulfment of apoptotic Jurkat T cells by NIH 3T3 fibroblasts at concentrations as low as 0.3 mM. Results represent mean ± SEM from three experiments.

Mentions: The above data suggests that the phagocytosis of apoptotic cells involves independent and separable events: particle tethering and engulfment. To investigate this further, we attempted to induce phagocytosis of adherent erythrocytes by secondary stimulation of the PSR. Erythrocytes were created that bound to the surface of NIH 3T3 fibroblasts by coating Eba with biotinylated anti-Dq/Lq MHC class I (Ebab–anti-MHC-I). These Ebab were not internalized in the absence of additional stimulation. Many growth factors, including EGF, PDGF, and macrophage colony–stimulating factor (M-CSF), stimulate the process of macropinocytosis (Brunk et al., 1976; Racoosin and Swanson, 1989; Hewlett et al., 1994), resulting in the ingestion of fluid, solutes, and macromolecules, as well as particles adhered to the cell surface (Galan et al., 1992). We observed that treatment of NIH 3T3 fibroblasts with EGF (or PDGF; unpublished data) stimulated the uptake of adherent Ebab–anti-MHC-I (Fig. 5 A). Similarly, treatment of HMDM with M-CSF triggered the uptake of Ebab–anti-CD36 (unpublished data).


Phosphatidylserine (PS) induces PS receptor-mediated macropinocytosis and promotes clearance of apoptotic cells.

Hoffmann PR, deCathelineau AM, Ogden CA, Leverrier Y, Bratton DL, Daleke DL, Ridley AJ, Fadok VA, Henson PM - J. Cell Biol. (2001)

PS- and PSR-mediated uptake of apoptotic cells occurs by a process akin to macropinocytosis. (A) To separately examine the tethering and engulfment events, Ebab were first allowed to tether to MHC-I on the phagocyte surface for 15 min, followed by stimulation with various forms of PS, anti-PSR antibody, or EGF (positive control) for 45 min. Ebab–anti-MHC-I were engulfed by fibroblasts when stimulated with EGF, anti-PSR, or POP-L-S, but not when stimulated with POP-D-S stereoisomer or PC. Results represent mean ± SEM from three experiments. (B) Amiloride, a specific inhibitor of macropinocytosis, inhibited the engulfment of apoptotic Jurkat T cells by NIH 3T3 fibroblasts at concentrations as low as 0.3 mM. Results represent mean ± SEM from three experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2198875&req=5

fig5: PS- and PSR-mediated uptake of apoptotic cells occurs by a process akin to macropinocytosis. (A) To separately examine the tethering and engulfment events, Ebab were first allowed to tether to MHC-I on the phagocyte surface for 15 min, followed by stimulation with various forms of PS, anti-PSR antibody, or EGF (positive control) for 45 min. Ebab–anti-MHC-I were engulfed by fibroblasts when stimulated with EGF, anti-PSR, or POP-L-S, but not when stimulated with POP-D-S stereoisomer or PC. Results represent mean ± SEM from three experiments. (B) Amiloride, a specific inhibitor of macropinocytosis, inhibited the engulfment of apoptotic Jurkat T cells by NIH 3T3 fibroblasts at concentrations as low as 0.3 mM. Results represent mean ± SEM from three experiments.
Mentions: The above data suggests that the phagocytosis of apoptotic cells involves independent and separable events: particle tethering and engulfment. To investigate this further, we attempted to induce phagocytosis of adherent erythrocytes by secondary stimulation of the PSR. Erythrocytes were created that bound to the surface of NIH 3T3 fibroblasts by coating Eba with biotinylated anti-Dq/Lq MHC class I (Ebab–anti-MHC-I). These Ebab were not internalized in the absence of additional stimulation. Many growth factors, including EGF, PDGF, and macrophage colony–stimulating factor (M-CSF), stimulate the process of macropinocytosis (Brunk et al., 1976; Racoosin and Swanson, 1989; Hewlett et al., 1994), resulting in the ingestion of fluid, solutes, and macromolecules, as well as particles adhered to the cell surface (Galan et al., 1992). We observed that treatment of NIH 3T3 fibroblasts with EGF (or PDGF; unpublished data) stimulated the uptake of adherent Ebab–anti-MHC-I (Fig. 5 A). Similarly, treatment of HMDM with M-CSF triggered the uptake of Ebab–anti-CD36 (unpublished data).

Bottom Line: Our results suggest that regardless of the receptors engaged on the phagocyte, ingestion does not occur in the absence of phosphatidylserine (PS).Further, recognition of PS was found to be dependent on the presence of the PS receptor (PSR).We propose that the phagocytosis of apoptotic cells requires two events: tethering followed by PS-stimulated, PSR-mediated macropinocytosis.

View Article: PubMed Central - PubMed

Affiliation: Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA.

ABSTRACT
Efficient phagocytosis of apoptotic cells is important for normal tissue development, homeostasis, and the resolution of inflammation. Although many receptors have been implicated in the clearance of apoptotic cells, the roles of these receptors in the engulfment process have not been well defined. We developed a novel system to distinguish between receptors involved in tethering of apoptotic cells versus those inducing their uptake. Our results suggest that regardless of the receptors engaged on the phagocyte, ingestion does not occur in the absence of phosphatidylserine (PS). Further, recognition of PS was found to be dependent on the presence of the PS receptor (PSR). Both PS and anti-PSR antibodies stimulated membrane ruffling, vesicle formation, and "bystander" uptake of cells bound to the surface of the phagocyte. We propose that the phagocytosis of apoptotic cells requires two events: tethering followed by PS-stimulated, PSR-mediated macropinocytosis.

Show MeSH
Related in: MedlinePlus