LRP1 mediates the Shh-induced endocytosis of the GPC3-Shh complex

Abstract

SummaryGlypican-3 (GPC3) is a heparan sulfate (HS) proteoglycan that is bound to the cell membrane through a glycosylphosphatidylinositol link. This glypican regulates embryonic growth by inhibiting the hedgehog (Hh) signaling pathway. GPC3 binds Hh and competes with Patched (Ptc), the Hh receptor, for Hh binding. The interaction of Hh with GPC3 triggers the endocytosis and degradation of the GPC3-Hh complex with the consequent reduction of Hh available for binding to Ptc. Currently, the molecular mechanisms by which the GPC3-Hh complex is internalized remains unknown. Here we show that the low-density-lipoprotein receptor-related protein-1 (LRP1) mediates the Hh-induced endocytosis of the GPC3-Hh complex, and that this endocytosis is necessary for the Hh-inhibitory activity of GPC3. Furthermore, we demonstrate that GPC3 binds through its HS chains to LRP1, and that this interaction causes the removal of GPC3 from the lipid rafts domains.

Processing by Convertases Is Required for Glypican-3-induced Inhibition of Hedgehog Signaling

“…Although it is well known that Hh binds with low affinity to HS, the core protein of GPC3 displays high affinity binding to Hh (5). Moreover, the interaction of Hh with GPC3 triggers the endocytosis and degradation of the GPC3-Hh complex, reducing the amount of Hh available to bind to Ptc (5,17).…”

“…Confocal images were generated using a scanning laser microscope LSM510 version 3.2 SP2 (Carl Zeiss) and a Zeiss LSM image browser. Image analysis was performed using the program ImageJ, as reported previously (17). Briefly, a mask, which was constructed by manually outlining cilia in the image of acetylated tubulin staining, was applied to GPC3/ GPC3 RR-AA-stained images to measure the fluorescence intensity at cilia.…”

Sortilin regulates sorting and secretion of Sonic hedgehog

“…We identified a number of new interacting candidates (Table S1) that were involved in diverse cellular functions, including intracellular sorting, receipt of extracellular ligands and protein maturation. The efficacy of the screen was confirmed by the identification of several known Shh interacting proteins, including low-density-lipoprotein receptorrelated protein-1 (Capurro et al, 2012) and glypican-5 (Gpc5) . Interestingly, we identified two members of the sortilin family, Sort1 and SorLA, in ShhC and ShhN pulldowns, respectively (Table S1).…”

An Unbiased Mass Spectrometry Approach Identifies Glypican-3 as an Interactor of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) and Low Density Lipoprotein Receptor (LDLR) in Hepatocellular Carcinoma Cells

“…Six proteins were selected from database data linking them to the following: (i) cholesterol homeostasis; (ii) interactions with LDLR family members; or (iii) an association with plasma LDL-C. It has been shown that cell-surface GPC3, TFPI, and PAI-1 can be internalized through an LRP1-dependent mechanism (31)(32)(33)(34)(35). TFPI and PLTP have been positively associated with LDL particles in human plasma (36,37), whereas PLTP has been mostly studied for its important role in HDL metabolism.…”