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Clathrin and LRP-1-independent constitutive endocytosis and recycling of uPAR

Cortese, Katia; Sahores, Macarena; Madsen, Chris D LU ; Tacchetti, Carlo and Blasi, Francesco (2008) In PLoS ONE 3(11).
Abstract

BACKGROUND: The urokinase receptor (uPAR/CD87) is highly expressed in malignant tumours. uPAR, as a GPI anchored protein, is preferentially located at the cell surface, where it interacts with its ligands urokinase (uPA) and the extracellular matrix protein vitronectin, thus promoting plasmin generation, cell-matrix interactions and intracellular signalling events. Interaction with a complex formed by uPA and its inhibitor PAI-1 induces cell surface down regulation and recycling of the receptor via the clathrin-coated pathway, a process dependent on the association to LRP-1.

METHODOLOGY/PRINCIPAL FINDINGS: In this study, we have found that along with the ligand-induced down-regulation, uPAR also internalizes and recycles... (More)

BACKGROUND: The urokinase receptor (uPAR/CD87) is highly expressed in malignant tumours. uPAR, as a GPI anchored protein, is preferentially located at the cell surface, where it interacts with its ligands urokinase (uPA) and the extracellular matrix protein vitronectin, thus promoting plasmin generation, cell-matrix interactions and intracellular signalling events. Interaction with a complex formed by uPA and its inhibitor PAI-1 induces cell surface down regulation and recycling of the receptor via the clathrin-coated pathway, a process dependent on the association to LRP-1.

METHODOLOGY/PRINCIPAL FINDINGS: In this study, we have found that along with the ligand-induced down-regulation, uPAR also internalizes and recycles constitutively through a second pathway that is independent of LRP-1 and clathrin but shares some properties with macropinocytosis. The ligand-independent route is amiloride-sensitive, does not require uPAR partitioning into lipid rafts, is independent of the activity of small GTPases RhoA, Rac1 and Cdc42, and does not require PI3K activity. Constitutively endocytosed uPAR is found in EEA1 positive early/recycling endosomes but does not reach lysosomes in the absence of ligands. Electron microscopy analysis reveals the presence of uPAR in ruffling domains at the cell surface, in macropinosome-like vesicles and in endosomal compartments.

CONCLUSIONS/SIGNIFICANCE: These results indicate that, in addition to the ligand-induced endocytosis of uPAR, efficient surface expression and membrane trafficking might also be driven by an uncommon macropinocytic mechanism coupled with rapid recycling to the cell surface.

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author
publishing date
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Contribution to journal
publication status
published
keywords
Amiloride, Cell Compartmentation, Cell Line, Clathrin, Dose-Response Relationship, Drug, Endocytosis, Endosomes, Humans, Ligands, Low Density Lipoprotein Receptor-Related Protein-1, Lysosomes, Membrane Microdomains, Monomeric GTP-Binding Proteins, Phosphatidylinositol 3-Kinases, Plasminogen Activator Inhibitor 1, Plasminogen Activators, Receptors, Urokinase Plasminogen Activator, Journal Article, Research Support, Non-U.S. Gov't
in
PLoS ONE
volume
3
issue
11
publisher
Public Library of Science
external identifiers
  • scopus:56649115742
ISSN
1932-6203
DOI
10.1371/journal.pone.0003730
language
English
LU publication?
no
id
8eb6a39c-1b7e-45c6-b140-97f74521ff14
date added to LUP
2016-12-06 10:17:19
date last changed
2017-04-16 04:42:39
@article{8eb6a39c-1b7e-45c6-b140-97f74521ff14,
  abstract     = {<p>BACKGROUND: The urokinase receptor (uPAR/CD87) is highly expressed in malignant tumours. uPAR, as a GPI anchored protein, is preferentially located at the cell surface, where it interacts with its ligands urokinase (uPA) and the extracellular matrix protein vitronectin, thus promoting plasmin generation, cell-matrix interactions and intracellular signalling events. Interaction with a complex formed by uPA and its inhibitor PAI-1 induces cell surface down regulation and recycling of the receptor via the clathrin-coated pathway, a process dependent on the association to LRP-1.</p><p>METHODOLOGY/PRINCIPAL FINDINGS: In this study, we have found that along with the ligand-induced down-regulation, uPAR also internalizes and recycles constitutively through a second pathway that is independent of LRP-1 and clathrin but shares some properties with macropinocytosis. The ligand-independent route is amiloride-sensitive, does not require uPAR partitioning into lipid rafts, is independent of the activity of small GTPases RhoA, Rac1 and Cdc42, and does not require PI3K activity. Constitutively endocytosed uPAR is found in EEA1 positive early/recycling endosomes but does not reach lysosomes in the absence of ligands. Electron microscopy analysis reveals the presence of uPAR in ruffling domains at the cell surface, in macropinosome-like vesicles and in endosomal compartments.</p><p>CONCLUSIONS/SIGNIFICANCE: These results indicate that, in addition to the ligand-induced endocytosis of uPAR, efficient surface expression and membrane trafficking might also be driven by an uncommon macropinocytic mechanism coupled with rapid recycling to the cell surface.</p>},
  articleno    = {e3730},
  author       = {Cortese, Katia and Sahores, Macarena and Madsen, Chris D and Tacchetti, Carlo and Blasi, Francesco},
  issn         = {1932-6203},
  keyword      = {Amiloride,Cell Compartmentation,Cell Line,Clathrin,Dose-Response Relationship, Drug,Endocytosis,Endosomes,Humans,Ligands,Low Density Lipoprotein Receptor-Related Protein-1,Lysosomes,Membrane Microdomains,Monomeric GTP-Binding Proteins,Phosphatidylinositol 3-Kinases,Plasminogen Activator Inhibitor 1,Plasminogen Activators,Receptors, Urokinase Plasminogen Activator,Journal Article,Research Support, Non-U.S. Gov't},
  language     = {eng},
  number       = {11},
  publisher    = {Public Library of Science},
  series       = {PLoS ONE},
  title        = {Clathrin and LRP-1-independent constitutive endocytosis and recycling of uPAR},
  url          = {http://dx.doi.org/10.1371/journal.pone.0003730},
  volume       = {3},
  year         = {2008},
}