Inhibition of endosomal insulin-like growth factor-I processing by cysteine proteinase inhibitors blocks receptor-mediated functions.
The receptor for the type 1 insulin-like growth factor (IGF-I) has been implicated in cellular transformation and the acquisition of an invasive/metastatic phenotype in various tumors. Following ligand binding, the IGF-I receptor is internalized, and the receptor.ligand complex dissociates as the ligand is degraded by endosomal proteinases. In the present study we show that the inhibition of endosomal IGF-I-degrading enzymes in human breast and murine lung carcinoma cells by the cysteine proteinase inhibitors, E-64 and CA074-methyl ester, profoundly altered receptor trafficking and signaling. In treated cells, intracellular ligand degradation was blocked, and although the receptor and two substrates, Shc and Insulin receptor substrate, were hyperphosphorylated on tyrosine, IGF-I-induced DNA synthesis, anchorage-independent growth, and matrix metalloproteinase synthesis were inhibited. The results suggest that ligand processing by endosomal proteinases is a key step in receptor signaling and function and a potential target for therapy.
Department of Surgery, McGill University Health Center, Royal Victoria Hospital, Montreal, Quebec H3A 1A4, Canada.
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R
Navab
E
E
Chevet
F
F
Authier
G M
GM
Di Guglielmo
J J
JJ
Bergeron
P
P
Brodt
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D011992:Endosomes / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008024:Ligands; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008954:Models, Biological; D009362:Neoplasm Metastasis; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C400541:CA 074 methyl ester; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D008024:Ligands; D011506:Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017526:Receptor, IGF Type 1; D007930:Leucine; C024974:E 64