title: Impact of Concanavalin-A-Mediated Cytoskeleton Disruption on Low-Density Lipoprotein Receptor-Related Protein-1 Internalization and Cell Surface Expression in Glioblastomas.
abstract: The low-density lipoprotein receptor-related protein 1 (LRP-1) is a multiligand endocytic receptor, which plays a pivotal role in controlling cytoskeleton dynamics during cancer cell migration. Its rapid endocytosis further allows efficient clearance of extracellular ligands. Concanavalin-A (ConA) is a lectin used to trigger in vitro physiological cellular processes, including cytokines secretion, nitric oxide production, and T-lymphocytes activation. Given that ConA exerts part of its effects through cytoskeleton remodeling, we questioned whether it affected LRP-1 expression, intracellular trafficking, and cell surface function in grade IV U87 glioblastoma cells. Using flow cytometry and confocal microscopy, we found that loss of the cell surface 600-kDa mature form of LRP-1 occurs upon ConA treatment. Consequently, internalization of the physiological α2-macroglobulin and the synthetic angiopep-2 ligands of LRP-1 was also decreased. Silencing of known mediators of ConA, such as the membrane type-1 matrix metalloproteinase, and the Toll-like receptors (TLR)-2 and TLR-6 was unable to rescue ConA-mediated LRP-1 expression decrease, implying that the loss of LRP-1 was independent of cell surface relayed signaling. The ConA-mediated reduction in LRP-1 expression was emulated by the actin cytoskeleton-disrupting agent cytochalasin-D, but not by the microtubule inhibitor nocodazole, and required both lysosomal- and ubiquitin-proteasome system-mediated degradation. Our study implies that actin cytoskeleton integrity is required for proper LRP-1 cell surface functions and that impaired trafficking leads to specialized compartmentation and degradation. Our data also strengthen the biomarker role of cell surface LRP-1 functions in the vectorized transport of therapeutic angiopep bioconjugates into brain cancer cells.
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Centre de recherche BIOMED, Département de Chimie, Université du Québec à Montréal, QC, Canada.
authors.forename: Samuel Burke
authors.initials: SB
authors.lastname: Nanni
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Centre de recherche BIOMED, Département de Chimie, Université du Québec à Montréal, QC, Canada.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Pratt
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Centre de recherche BIOMED, Département de Chimie, Université du Québec à Montréal, QC, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Beauchemin
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Centre de recherche BIOMED, Département de Chimie, Université du Québec à Montréal, QC, Canada.
authors.forename: Khadidja
authors.initials: K
authors.lastname: Haidara
authors.affiliation: Laboratoire d'Oncologie Moléculaire, Centre de recherche BIOMED, Département de Chimie, Université du Québec à Montréal, QC, Canada.
authors.forename: Borhane
authors.initials: B
authors.lastname: Annabi
keywords: LRP-1; brain cancer; concanavalin-A; cytoskeleton; glioblastoma