Purified alpha 2-macroglobulin receptor/LDL receptor-related protein binds urokinase.plasminogen activator inhibitor type-1 complex. Evidence that the alpha 2-macroglobulin receptor mediates cellular degradation of urokinase receptor-bound complexes.

Nykjær, Anders; Petersen, Claus Munck; Møller, Bjarne Kuno; Jensen, Poul Henning; Moestrup, Søren K.; Holtet, Thor L.; Etzerodt, Michael; Thøgersen, Hans C.; Munch, Mette; Andreasen, Peter A.

doi:10.1016/s0021-9258(18)42072-8

Cited by 438 publications

(32 citation statements)

References 35 publications

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“…The receptor for uPA has the peculiar property of inducing the internalization of some (uPA-serpin complexes) but not other ligands (uPA, pro-uPA, DFP-uPA, ATF) (Cubellis et al, 1990). This property is acquired because the serpin moiety can interact with the LRP/a2-MR or other members of the LDL receptor gene family (Nykjaer et al, 1992;Herz et al, 1992;Moestrup et al, 1993a;Kounnas et al, 1993;Li et al, 1994). Previous studies have shown that uPAR binding represents the first and essential step for an efficient degradation of uPA-serpin complexes in human U937 cells and in murine LB6 clone 19 cells (Olson et al, 1992;Conese et al, 1994).…”

Section: Discussionmentioning

confidence: 99%

alpha-2 Macroglobulin receptor/Ldl receptor-related protein(Lrp)-dependent internalization of the urokinase receptor.

Conese

Nykjær

Petersen

et al. 1995

The Journal of Cell Biology

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189

183

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Abstract. The GPI-anchored urokinase plasminogen activator receptor (uPAR) does not internalize free urokinase (uPA). On the contrary, uPAR-bound complexes of uPA with its serpin inhibitors PAI-1 (plasminogen activator inhibitor type-l) or PN-1 (protease nexin-1) are readily internalized in several cell types. Here we address the question whether uPAR is internalized as well upon binding of uPA-serpin complexes. Both LB6 clone 19 cells, a mouse cell line transfected with the human uPAR cDNA, and the human U937 monocytic cell line, express in addition to uPAR also the endocytic et2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP/a2-MR) which is required to internalize uPAR-bound uPA-PAI-1 and uPA-PN-1 complexes. Downregulation of cell surface uPAR molecules in U937 cells was detected by cytofluorimetric analysis after uPA-PAI-1 and uPA-PN-1 incubation for 30 min at 37°C; this effect was blocked by preincubation with the ligand of LRP/ aE-MR, RAP (LRP/a2-MR-associated protein), known to block the binding of the uPA complexes to LRP/et E-MR. Downregulation correlated in time with the intracellular appearance of uPAR as assessed by confocal microscopy and immuno-electron microscopy. After 30 min incubation with uPA-PAI-1 or uPA-PN-1 (but not with free uPA), confocal microscopy showed that uPAR staining in permeabilized LB6 clone 19 cells moved from a mostly surface associated to a largely perinuclear position. This effect was inhibited by the LRP/a2-MR RAP. Perinuclear uPAR did not represent newly synthesized nor a preexisting intracellular pool of uPAR, since this fluorescence pattern was not modified by treatment with the protein synthesis inhibitor cycloheximide, and since in LB6 clone 19 cells all of uPAR was expressed on the cell surface. Immuno-electron microscopy confirmed the plasma membrane to intracellular translocation of uPAR, and its dependence on LRP/ot2-MR in LB6 clone 19 cells only after binding to the uPA-PAI-1 complex. After 30 min incubation at 37°C with uPA-PAI-1, 93 % of the specific immunogold particles were present in cytoplasmic vacuoles vs 17.6% in the case of DFP-uPA. We conclude therefore that in the process of uPA-serpin internalization, uPAR itself is internalized, and that internalization requires the LRP/a2-MR.

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Section: Discussionmentioning

confidence: 99%

alpha-2 Macroglobulin receptor/Ldl receptor-related protein(Lrp)-dependent internalization of the urokinase receptor.

Conese

Nykjær

Petersen

et al. 1995

The Journal of Cell Biology

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189

183

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“…This study also showed that mLRP1B4, similar to mLRP4, could bind uPA/PAI-1/uPAR complexes and internalize them [ 25 ]. By then, it was known that after the internalization of the uPA/PAI-1/uPAR complexes mediated by LRP1, the uPA/PAI-1 complexes were trafficked to lysosomes for degradation, and the unoccupied (ligand-free and active) forms of LRP1 and uPAR were recycled back to the cell surface [ 42 , 43 , 44 , 45 ]. However, mLRP1B4-expressing cells, compared with mLRP4-expressing cells, showed a substantially reduced capacity to recycle unoccupied uPAR to the cell surface, which was consistent with the functional difference in the internalization rates of the LRP1 and LRP1B mini-receptors [ 25 ], and to migrate.…”

Section: Low-density Lipoprotein (Ldl) Receptor (Ldrl)-related Protein 1b (Lrp1b)mentioning

confidence: 99%

LRP1B: A Giant Lost in Cancer Translation

et al. 2021

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Low-density lipoprotein receptor-related protein 1B (LRP1B) is a giant member of the LDLR protein family, which includes several structurally homologous cell surface receptors with a wide range of biological functions from cargo transport to cell signaling. LRP1B is among the most altered genes in human cancer overall. Found frequently inactivated by several genetic and epigenetic mechanisms, it has mostly been regarded as a putative tumor suppressor. Still, limitations in LRP1B studies exist, in particular associated with its huge size. Therefore, LRP1B expression and function in cancer remains to be fully unveiled. This review addresses the current understanding of LRP1B and the studies that shed a light on the LRP1B structure and ligands. It goes further in presenting increasing knowledge brought by technical and methodological advances that allow to better manipulate LRP1B expression in cells and to more thoroughly explore its expression and mutation status. New evidence is pushing towards the increased relevance of LRP1B in cancer as a potential target or translational prognosis and response to therapy biomarkers.

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“…PAI1 exerts its activity through a covalent binding and inactivation of uPA. After binding to uPAR, the uPA-PAI1 complex is internalized by a mechanism that involves one or more members of the lowdensity lipoprotein receptor family, including LRP1 (Cubellis et al, 1990;Nykjaer et al, 1992). After internalization, the uPA-PAI1 complex is degraded in lysosomes, and uPAR recycles to the cell surface (Conese and Blasi, 1995;Nykjaer et al, 1997).…”

Section: Binding Of Upa-pai1 Endocytosis and Recycling Affect Dimerization And Dynamics Of Uparmentioning

confidence: 99%

Monomer–dimer dynamics and distribution of GPI-anchored uPAR are determined by cell surface protein assemblies

Caiolfa

Zamai

Malengo

et al. 2007

The Journal of Cell Biology

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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.

show abstract

Purified alpha 2-macroglobulin receptor/LDL receptor-related protein binds urokinase.plasminogen activator inhibitor type-1 complex. Evidence that the alpha 2-macroglobulin receptor mediates cellular degradation of urokinase receptor-bound complexes.

Cited by 438 publications

References 35 publications

alpha-2 Macroglobulin receptor/Ldl receptor-related protein(Lrp)-dependent internalization of the urokinase receptor.

alpha-2 Macroglobulin receptor/Ldl receptor-related protein(Lrp)-dependent internalization of the urokinase receptor.

LRP1B: A Giant Lost in Cancer Translation

Monomer–dimer dynamics and distribution of GPI-anchored uPAR are determined by cell surface protein assemblies

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