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FASEB J. 2016 Mar;30(3):1218-33. doi: 10.1096/fj.15-276311. Epub 2015 Nov 30.

L-plastin Ser5 phosphorylation in breast cancer cells and in vitro is mediated by RSK downstream of the ERK/MAPK pathway.

Author information

1
*Laboratory of Cytoskeleton and Cell Plasticity and Systems Biology Group, Life Sciences Research Unit, University of Luxembourg, Luxembourg City, Luxembourg; and Genomics Research Unit, Luxembourg Institute of Health, Luxembourg City, Luxembourg.
2
*Laboratory of Cytoskeleton and Cell Plasticity and Systems Biology Group, Life Sciences Research Unit, University of Luxembourg, Luxembourg City, Luxembourg; and Genomics Research Unit, Luxembourg Institute of Health, Luxembourg City, Luxembourg elisabeth.schaffner@uni.lu.

Abstract

Deregulated cell migration and invasion are hallmarks of metastatic cancer cells. Phosphorylation on residue Ser5 of the actin-bundling protein L-plastin activates L-plastin and has been reported to be crucial for invasion and metastasis. Here, we investigate signal transduction leading to L-plastin Ser5 phosphorylation using 4 human breast cancer cell lines. Whole-genome microarray analysis comparing cell lines with different invasive capacities and corresponding variations in L-plastin Ser5 phosphorylation level revealed that genes of the ERK/MAPK pathway are differentially expressed. It is noteworthy that in vitro kinase assays showed that ERK/MAPK pathway downstream ribosomal protein S6 kinases α-1 (RSK1) and α-3 (RSK2) are able to directly phosphorylate L-plastin on Ser5. Small interfering RNA- or short hairpin RNA-mediated knockdown and activation/inhibition studies followed by immunoblot analysis and computational modeling confirmed that ribosomal S6 kinase (RSK) is an essential activator of L-plastin. Migration and invasion assays showed that RSK knockdown led to a decrease of up to 30% of migration and invasion of MDA-MB-435S cells. Although the presence of L-plastin was not necessary for migration/invasion of these cells, immunofluorescence assays illustrated RSK-dependent recruitment of Ser5-phosphorylated L-plastin to migratory structures. Altogether, we provide evidence that the ERK/MAPK pathway is involved in L-plastin Ser5 phosphorylation in breast cancer cells with RSK1 and RSK2 kinases able to directly phosphorylate L-plastin residue Ser5.

KEYWORDS:

actin cytoskeleton; invasion; migration; signal transduction

PMID:
26631483
DOI:
10.1096/fj.15-276311
[Indexed for MEDLINE]

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