Pro-cathepsin D interacts with the extracellular domain of the beta chain of LRP1 and promotes LRP1-dependent fibroblast outgrowth.

Abstract

Interactions between cancer cells and fibroblasts are crucial in cancer progression. We have previously shown that the aspartic protease cathepsin D (cath-D), a marker of poor prognosis in breast cancer that is overexpressed and highly secreted by breast cancer cells, triggers mouse embryonic fibroblast outgrowth via a paracrine loop. Here, we show the requirement of secreted cath-D for human mammary fibroblast outgrowth using a three-dimensional co-culture assay with breast cancer cells that do or do not secrete pro-cath-D. Interestingly, proteolytically-inactive pro-cath-D remains mitogenic, indicating a mechanism involving protein-protein interaction. We identify the low-density lipoprotein (LDL) receptor-related protein-1, LRP1, as a novel binding partner for pro-cath-D in fibroblasts. Pro-cath-D binds to residues 349-394 of the β chain of LRP1, and is the first ligand of the extracellular domain of LRP1β to be identified. We show that pro-cath-D interacts with LRP1β in cellulo. Interaction occurs at the cell surface, and overexpressed LRP1β directs pro-cath-D to the lipid rafts. Our results reveal that the ability of secreted pro-cath-D to promote human mammary fibroblast outgrowth depends on LRP1 expression, suggesting that pro-cath-D-LRP1β interaction plays a functional role in the outgrowth of fibroblasts. Overall, our findings strongly suggest that pro-cath-D secreted by epithelial cancer cells promotes fibroblast outgrowth in a paracrine LRP1-dependent manner in the breast tumor microenvironment.

• Authors: Mélanie Beaujouin, Christine Prébois, Danielle Derocq, Valérie Laurent-Matha, Olivier Masson, Sophie Pattingre, Peter Coopman, Nadir Bettache, Jami Grossfield, Robert E Hollingsworth, Hongyu Zhang, Zemin Yao, Bradley T Hyman, Peter van der Geer, Gary K Smith, Emmanuelle Liaudet-Coopman
• Journal: Journal of cell science (J Cell Sci) Vol. 123 Issue Pt 19 Pg. 3336-46 (Oct 01 2010) ISSN: 1477-9137 [Electronic] England
• PMID: 20826454 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, CD
• Enzyme Precursors
• LRP1 protein, human
• Low Density Lipoprotein Receptor-Related Protein-1
• RNA, Small Interfering
• procathepsin D
• Cathepsin D

Topics

• Animals
• Antigens, CD (genetics, metabolism)
• Breast Neoplasms (metabolism, pathology)
• Carcinoma (metabolism, pathology)
• Cathepsin D (metabolism)
• Cell Growth Processes
• Cell Line, Transformed
• Coculture Techniques
• Enzyme Precursors (metabolism)
• Female
• Fibroblasts (metabolism, pathology)
• Humans
• Low Density Lipoprotein Receptor-Related Protein-1 (genetics, metabolism)
• Membrane Microdomains (genetics)
• Mice
• Paracrine Communication
• Protein Binding
• Protein Interaction Domains and Motifs (genetics)
• RNA, Small Interfering (genetics)