Monomer dimer dynamics and distribution of GPI-anchored uPAR are determined by cell surface protein assemblies.
To search for functional links between glycosylphosphatidylinositol (GPI) protein monomer-oligomer exchange and membrane dynamics and confinement, we studied urokinase plasminogen activator (uPA) receptor (uPAR), a GPI receptor involved in the regulation of cell adhesion, migration, and proliferation. Using a functionally active fluorescent protein-uPAR in live cells, we analyzed the effect that extracellular matrix proteins and uPAR ligands have on uPAR dynamics and dimerization at the cell membrane. Vitronectin directs the recruitment of dimers and slows down the diffusion of the receptors at the basal membrane. The commitment to uPA-plasminogen activator inhibitor type 1-mediated endocytosis and recycling modifies uPAR diffusion and induces an exchange between uPAR monomers and dimers. This exchange is fully reversible. The data demonstrate that cell surface protein assemblies are important in regulating the dynamics and localization of uPAR at the cell membrane and the exchange of monomers and dimers. These results also provide a strong rationale for dynamic studies of GPI-anchored molecules in live cells at steady state and in the absence of cross-linker/clustering agents.
Department of Molecular Biology and Functional Genomics, Unit of Molecular Neuroscience, San Raffaele Scientific Institute, 20132 Milano, Italy. valeria.caiolfa@hsr.it
Valeria R
VR
Caiolfa
Moreno
M
Zamai
Gabriele
G
Malengo
Annapaola
A
Andolfo
Chris D
CD
Madsen
Jason
J
Sutin
Michelle A
MA
Digman
Enrico
E
Gratton
Francesco
F
Blasi
Nicolai
N
Sidenius
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004058:Diffusion; D019281:Dimerization; D004705:Endocytosis; D005109:Extracellular Matrix / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D044967:Serum; D019096:Vitronectin / Q000378:metabolism
D017261:Glycosylphosphatidylinositols; C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D019096:Vitronectin