Reference : L-plastin Ser5 phosphorylation is modulated by the PI3K/SGK pathway and promotes brea...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
L-plastin Ser5 phosphorylation is modulated by the PI3K/SGK pathway and promotes breast cancer cell invasiveness
Machado, Raquel A.C. mailto [University of Toronto - U of T > Structural Genomics Consortium SGC > > PhD]
Stojevski, Dunja mailto [Siemens Healthineers > > > MSc]
de Landtsheer, Sébastien mailto [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Life Science Research Unit >]
Lucarelli, Philippe mailto [Gerresheimer AG > Sensile Medical AG > > PhD]
Baron, Alexandre mailto [Luxembourg Institute of Health - LIH > Department of Infection and Immunity > Immune Systems Biology > MSc]
Sauter, Thomas mailto [University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Life Sciences and Medicine (DLSM) >]
Schaffner-Reckinger, Elisabeth mailto [University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Life Sciences and Medicine (DLSM) >]
Cell Communication and Signaling
BioMed Central
United Kingdom
[en] L-plastin ; Actin-bundling ; PI3K pathway ; ERK/MAPK pathway ; SGK ; RSK ; Invasion ; Invadopodia ; Extracellular matrix degradation ; Metastasis
[en] Background: Metastasis is the predominant cause for cancer morbidity and mortality accounting for approxima‑ tively 90% of cancer deaths. The actin‑bundling protein L‑plastin has been proposed as a metastatic marker and phos‑ phorylation on its residue Ser5 is known to increase its actin‑bundling activity. We recently showed that activation of the ERK/MAPK signalling pathway leads to L‑plastin Ser5 phosphorylation and that the downstream kinases RSK1 and RSK2 are able to directly phosphorylate Ser5. Here we investigate the involvement of the PI3K pathway in L‑plastin Ser5 phosphorylation and the functional effect of this phosphorylation event in breast cancer cells.
Methods: To unravel the signal transduction network upstream of L‑plastin Ser5 phosphorylation, we performed computational modelling based on immunoblot analysis data, followed by experimental validation through inhi‑ bition/overexpression studies and in vitro kinase assays. To assess the functional impact of L‑plastin expression/
Ser5 phosphorylation in breast cancer cells, we either silenced L‑plastin in cell lines initially expressing endogenous L‑plastin or neoexpressed L‑plastin wild type and phosphovariants in cell lines devoid of endogenous L‑plastin. The established cell lines were used for cell biology experiments and confocal microscopy analysis.
Results: Our modelling approach revealed that, in addition to the ERK/MAPK pathway and depending on the cellular context, the PI3K pathway contributes to L‑plastin Ser5 phosphorylation through its downstream kinase SGK3. The results of the transwell invasion/migration assays showed that shRNA‑mediated knockdown of L‑plastin in BT‑20 or HCC38 cells significantly reduced cell invasion, whereas stable expression of the phosphomimetic L‑plastin Ser5Glu variant led to increased migration and invasion of BT‑549 and MDA‑MB‑231 cells. Finally, confocal image analysis combined with zymography experiments and gelatin degradation assays provided evidence that L‑plastin Ser5 phosphorylation promotes L‑plastin recruitment to invadopodia, MMP‑9 activity and concomitant extracellular matrix degradation.
Conclusion: Altogether, our results demonstrate that L‑plastin Ser5 phosphorylation increases breast cancer cell invasiveness. Being a downstream molecule of both ERK/MAPK and PI3K/SGK pathways, L‑plastin is proposed here as a potential target for therapeutic approaches that are aimed at blocking dysregulated signalling outcome of both pathways and, thus, at impairing cancer cell invasion and metastasis formation.
Fondation Cancer Luxembourg (FC/2016/04)
Analysis of the signal transduction network upstream of L-plastin Ser5 phosphorylation in breast cancer cells and tissues
Researchers ; Professionals ; Students

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