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An electrostatic switch displaces phosphatidylinositol phosphate kinases from the membrane during phagocytosis.

Fairn GD, Ogata K, Botelho RJ, Stahl PD, Anderson RA, De Camilli P, Meyer T, Wodak S, Grinstein S - J. Cell Biol. (2009)

Bottom Line: During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased.Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup.We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Program in Cell Biology and 2 Structural Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada M5G1X8.

ABSTRACT
Plasmalemmal phosphatidylinositol (PI) 4,5-bisphosphate (PI4,5P(2)) synthesized by PI 4-phosphate (PI4P) 5-kinase (PIP5K) is key to the polymerization of actin that drives chemotaxis and phagocytosis. We investigated the means whereby PIP5K is targeted to the membrane and its fate during phagosome formation. Homology modeling revealed that all PIP5K isoforms feature a positively charged face. Together with the substrate-binding loop, this polycationic surface is proposed to constitute a coincidence detector that targets PIP5Ks to the plasmalemma. Accordingly, manipulation of the surface charge displaced PIP5Ks from the plasma membrane. During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased. Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup. Chemically induced retention of PIP5K-gamma prevented the disappearance of PI4,5P(2) and aborted phagosome formation. We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.

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Schematic representation of the changes in phospholipid content and surface charge during phagocytosis. Proposed changes in the content of PI4,5P2 (blue), PI3,4,5P3 (yellow), and surface charge of the membrane (red) during the various stages of phagocytosis shown chronologically from top to bottom.
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fig8: Schematic representation of the changes in phospholipid content and surface charge during phagocytosis. Proposed changes in the content of PI4,5P2 (blue), PI3,4,5P3 (yellow), and surface charge of the membrane (red) during the various stages of phagocytosis shown chronologically from top to bottom.

Mentions: In view of the preceding considerations, we envisage the following sequence of events: (a) upon engagement of phagocytic receptors, PIP5K is initially activated, possibly by the localized accumulation of phosphatidic acid (Corrotte et al., 2006) and/or by the stimulation of Rho family GTPases (Chong et al., 1994), resulting in elevated PI4,5P2. Phosphatidylinositol 3-kinase is also activated by the receptors at an early stage. (b) PI3,4,5P3-mediated recruitment and tyrosine phosphorylation of PLC-γ activate the hydrolysis of PI4,5P2, which in turn reduces the surface charge of the phagosomal membrane; and (c) PIP5Ks dissociate from the membrane in response to the drop in surface charge, thereby terminating PI4,5P2 synthesis and contributing to catastrophic depletion of this phosphoinositide. The resulting positive feedback loop accelerates the depolymerization of actin, favoring completion of phagocytosis. The results demonstrate that a feedback loop can accelerate the displacement of PIP5Ks from the membrane and can also reduce the membrane surface charge despite the presence of PI4P. These changes are diagrammatically illustrated in Fig. 8.


An electrostatic switch displaces phosphatidylinositol phosphate kinases from the membrane during phagocytosis.

Fairn GD, Ogata K, Botelho RJ, Stahl PD, Anderson RA, De Camilli P, Meyer T, Wodak S, Grinstein S - J. Cell Biol. (2009)

Schematic representation of the changes in phospholipid content and surface charge during phagocytosis. Proposed changes in the content of PI4,5P2 (blue), PI3,4,5P3 (yellow), and surface charge of the membrane (red) during the various stages of phagocytosis shown chronologically from top to bottom.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2806594&req=5

fig8: Schematic representation of the changes in phospholipid content and surface charge during phagocytosis. Proposed changes in the content of PI4,5P2 (blue), PI3,4,5P3 (yellow), and surface charge of the membrane (red) during the various stages of phagocytosis shown chronologically from top to bottom.
Mentions: In view of the preceding considerations, we envisage the following sequence of events: (a) upon engagement of phagocytic receptors, PIP5K is initially activated, possibly by the localized accumulation of phosphatidic acid (Corrotte et al., 2006) and/or by the stimulation of Rho family GTPases (Chong et al., 1994), resulting in elevated PI4,5P2. Phosphatidylinositol 3-kinase is also activated by the receptors at an early stage. (b) PI3,4,5P3-mediated recruitment and tyrosine phosphorylation of PLC-γ activate the hydrolysis of PI4,5P2, which in turn reduces the surface charge of the phagosomal membrane; and (c) PIP5Ks dissociate from the membrane in response to the drop in surface charge, thereby terminating PI4,5P2 synthesis and contributing to catastrophic depletion of this phosphoinositide. The resulting positive feedback loop accelerates the depolymerization of actin, favoring completion of phagocytosis. The results demonstrate that a feedback loop can accelerate the displacement of PIP5Ks from the membrane and can also reduce the membrane surface charge despite the presence of PI4P. These changes are diagrammatically illustrated in Fig. 8.

Bottom Line: During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased.Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup.We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Program in Cell Biology and 2 Structural Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada M5G1X8.

ABSTRACT
Plasmalemmal phosphatidylinositol (PI) 4,5-bisphosphate (PI4,5P(2)) synthesized by PI 4-phosphate (PI4P) 5-kinase (PIP5K) is key to the polymerization of actin that drives chemotaxis and phagocytosis. We investigated the means whereby PIP5K is targeted to the membrane and its fate during phagosome formation. Homology modeling revealed that all PIP5K isoforms feature a positively charged face. Together with the substrate-binding loop, this polycationic surface is proposed to constitute a coincidence detector that targets PIP5Ks to the plasmalemma. Accordingly, manipulation of the surface charge displaced PIP5Ks from the plasma membrane. During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased. Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup. Chemically induced retention of PIP5K-gamma prevented the disappearance of PI4,5P(2) and aborted phagosome formation. We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.

Show MeSH
Related in: MedlinePlus