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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: 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.

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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Presence of PS on the surface of tethered Ebab results in their uptake in a stereo-specific manner. Erythrocytes coated with PS (or PC, as a control) were incubated with HMDM. All results represent mean ± SEM. from three or more experiments. (A) Addition of PS, but not PC, to erythrocytes resulted in little tethering or uptake by HMDM. Addition of PS to various Ebab induced their engulfment by HMDM, whereas PC had no effect. (B) To address the stereo specificity of PS-mediated Ebab engulfment, POP-L-S or POP-D-S was added to the erythrocyte membrane. Addition of POP-L-S induced uptake of tethered Ebab by HMDM to similar levels observed with bovine brain PS, whereas POP-D-S did not. (C) Preincubation of HMDM with anti-PSR antibodies blocked the engulfment of PS-coated Ebab, but minimally affected engulfment of Ebab via FcγR. Preincubation of HMDM with other IgM antibodies did not block engulfment of PS-coated Ebab. ▪, Engulfed; □, tethered.
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fig3: Presence of PS on the surface of tethered Ebab results in their uptake in a stereo-specific manner. Erythrocytes coated with PS (or PC, as a control) were incubated with HMDM. All results represent mean ± SEM. from three or more experiments. (A) Addition of PS, but not PC, to erythrocytes resulted in little tethering or uptake by HMDM. Addition of PS to various Ebab induced their engulfment by HMDM, whereas PC had no effect. (B) To address the stereo specificity of PS-mediated Ebab engulfment, POP-L-S or POP-D-S was added to the erythrocyte membrane. Addition of POP-L-S induced uptake of tethered Ebab by HMDM to similar levels observed with bovine brain PS, whereas POP-D-S did not. (C) Preincubation of HMDM with anti-PSR antibodies blocked the engulfment of PS-coated Ebab, but minimally affected engulfment of Ebab via FcγR. Preincubation of HMDM with other IgM antibodies did not block engulfment of PS-coated Ebab. ▪, Engulfed; □, tethered.

Mentions: Construction of Ebab–anti-PSR was not possible because the biotinylation of our monoclonal antibody (mAb 217) destroyed its ability to bind the receptor (unpublished data). Therefore, we used erythrocytes coated with PS to investigate the role of the PSR in binding versus uptake of particles. PS alone was not sufficient to mediate adhesion or engulfment of the erythrocytes. However, when membrane PS was combined with any of the ligands capable of tethering the Ebab to macrophages, adhesion was converted into engulfment (Fig. 3 A). PS on the surface of Ebab was sufficient to drive uptake even when Ebab were tethered to CD59, a surface molecule not thought to be involved in phagocytosis. This effect was also seen when PS-coated Ebab were tethered to NIH 3T3 fibroblasts (Ebab–anti-major histocompatibility complex [MHC]-I) or MPM (or Ebab–anti-F4/80-antigen; unpublished data). These results suggest that even though PS on the surface of a particle alone is not sufficient to confer particle binding, its presence is sufficient to trigger the engulfment of a tethered particle regardless of the initial adhesive ligand.


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)

Presence of PS on the surface of tethered Ebab results in their uptake in a stereo-specific manner. Erythrocytes coated with PS (or PC, as a control) were incubated with HMDM. All results represent mean ± SEM. from three or more experiments. (A) Addition of PS, but not PC, to erythrocytes resulted in little tethering or uptake by HMDM. Addition of PS to various Ebab induced their engulfment by HMDM, whereas PC had no effect. (B) To address the stereo specificity of PS-mediated Ebab engulfment, POP-L-S or POP-D-S was added to the erythrocyte membrane. Addition of POP-L-S induced uptake of tethered Ebab by HMDM to similar levels observed with bovine brain PS, whereas POP-D-S did not. (C) Preincubation of HMDM with anti-PSR antibodies blocked the engulfment of PS-coated Ebab, but minimally affected engulfment of Ebab via FcγR. Preincubation of HMDM with other IgM antibodies did not block engulfment of PS-coated Ebab. ▪, Engulfed; □, tethered.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2198875&req=5

fig3: Presence of PS on the surface of tethered Ebab results in their uptake in a stereo-specific manner. Erythrocytes coated with PS (or PC, as a control) were incubated with HMDM. All results represent mean ± SEM. from three or more experiments. (A) Addition of PS, but not PC, to erythrocytes resulted in little tethering or uptake by HMDM. Addition of PS to various Ebab induced their engulfment by HMDM, whereas PC had no effect. (B) To address the stereo specificity of PS-mediated Ebab engulfment, POP-L-S or POP-D-S was added to the erythrocyte membrane. Addition of POP-L-S induced uptake of tethered Ebab by HMDM to similar levels observed with bovine brain PS, whereas POP-D-S did not. (C) Preincubation of HMDM with anti-PSR antibodies blocked the engulfment of PS-coated Ebab, but minimally affected engulfment of Ebab via FcγR. Preincubation of HMDM with other IgM antibodies did not block engulfment of PS-coated Ebab. ▪, Engulfed; □, tethered.
Mentions: Construction of Ebab–anti-PSR was not possible because the biotinylation of our monoclonal antibody (mAb 217) destroyed its ability to bind the receptor (unpublished data). Therefore, we used erythrocytes coated with PS to investigate the role of the PSR in binding versus uptake of particles. PS alone was not sufficient to mediate adhesion or engulfment of the erythrocytes. However, when membrane PS was combined with any of the ligands capable of tethering the Ebab to macrophages, adhesion was converted into engulfment (Fig. 3 A). PS on the surface of Ebab was sufficient to drive uptake even when Ebab were tethered to CD59, a surface molecule not thought to be involved in phagocytosis. This effect was also seen when PS-coated Ebab were tethered to NIH 3T3 fibroblasts (Ebab–anti-major histocompatibility complex [MHC]-I) or MPM (or Ebab–anti-F4/80-antigen; unpublished data). These results suggest that even though PS on the surface of a particle alone is not sufficient to confer particle binding, its presence is sufficient to trigger the engulfment of a tethered particle regardless of the initial adhesive ligand.

Bottom Line: 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.

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