Liprin-α1 regulates breast cancer cell invasion by affecting cell motility, invadopodia and extracellular matrix degradation

Abstract

Migration of cells and degradation of the extracellular matrix (ECM) are required for efficient tumor cell invasion, but the underlying molecular mechanisms are only partially known. The PPFIA1 gene for liprin-a1 is frequently amplified in human breast cancers. We recently demonstrated that liprin-a1 is an important regulator of cell edge dynamics during motility. We show, herein, that the liprin-a1 protein is highly expressed in human breast tumors. Functional analysis shows that liprin-a1 is specifically required for the migration and invasion of highly invasive human breast cancer MDA-MB-231 cells. We used time-lapse analysis to demonstrate defects in the motility of liprin-a1-depleted cells that include a striking instability of the lamellipodia. Liprin-a1 levels altered by either RNA interference or overexpression affected also cell spreading and the number of invadopodia per cell, but not the density of invadopodia per unit of surface area. On the other hand, silencing of liprin-a1 inhibited the degradation of the ECM, whereas its overexpression enhanced degradation, resulting in significant negative or positive effects, respectively, on the area of degradation per invadopodium. Transfection of fluorescent-labeled cortactin revealed that depletion of liprin-a1 also affected the assembly and disassembly of invadopodia, with decrease of their lifetime. Our results strongly support a novel important role of liprin-a1 in the regulation of human tumor cell invasion.

Liprin-α1, ERC1 and LL5 identify a polarized, dynamic compartment implicated in cell migration

“…2A), as previously observed after liprin-a1 silencing (Astro et al, 2011). Depletion of either protein induced the appearance of lamellipodia more frequently, but these lamellipodia were less persistent (Fig.…”

“…MDA-231 cells (10 5 cells) in fibronectin-coated (2.5 mg/ml) coverlips were transfected after 1 day, and used for video imaging or immunofluorescence 24-48 h later (Astro et al, 2011). Live imaging was performed on Inverted Eclipse TE2000-E microscope (Nikon) with a spinning-disc head (CSU-10, Yokogawa) equipped with a Cool SNAP HQ2 CCD camera (Photometrics).…”

“…siRNAs (Life Technologies) for luciferase, liprin-a1, ERC1a, LL5b and LL5a were as described previously (Asperti et al, 2009;Lansbergen et al, 2006;Ducut Sigala et al, 2004;Hotta et al, 2010;Astro et al, 2011). The region targeted by siRNA for human LL5b includes two mismatches with respect to the mouse cDNA sequence, making this latter resistant to silencing.…”

“…Haptotactic migration, cell spreading, and invasion assays were as described previously (Astro et al, 2011). Data were normalized to control and presented as means6s.e.m.…”

“…Its polypeptide is highly expressed in human breast cancer and other types of human tumors (Rezaul et al, 2010;Astro et al, 2011). Moreover, liprin-a1 is needed for breast cancer cell motility and invasion in vitro (Astro et al, 2011), and is an important regulator of focal adhesion turnover and lamellipodial dynamics. To further dissect the role of liprin-a1 in cell motility, we have looked for relevant liprin-a1-interacting partners.…”