Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The low-density-lipoprotein-receptor-related protein (LRP) binds and internalizes numerous ligands, including lipoproteins, proteinase-inhibitor complexes and others. We have shown previously that LRP-mediated ligand internalization is dependent on cAMP-dependent protein kinase (PKA) activity. Here, we investigated whether ligation of LRP increases the intracellular cAMP level and PKA activity via a stimulatory GTP-binding protein. Treatment of LRP-expressing cell lines with the LRP ligands lactoferrin or urokinase-type plasminogen activator caused a significant elevation in cAMP and stimulated PKA activity in a dose-dependent manner. Addition of the 39 kDa receptor-associated protein (RAP), an antagonist for ligand interactions with LRP, blocked the lactoferrin-induced increase in PKA activity, demonstrating a requirement for ligand binding to LRP. Incubation of cell membrane fractions with lactoferrin increased GTPase activity in a time- and dose-dependent manner, and treatment with LRP ligands suppressed cholera-toxin-mediated ADP-ribosylation of the Gsalpha subunit of a heterotrimeric G-protein. Affinity precipitation of LRP with RAP resulted in co-precipitation of two isoforms of Gsalpha from detergent extracts. We thus conclude that LRP is a signalling receptor that associates directly with a stimulatory heterotrimeric G-protein and activates a downstream PKA-dependent pathway.
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PMID:Low-density-lipoprotein-receptor-related protein (LRP) interacts with a GTP-binding protein. 982 Aug 15


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