title: L-plastin Ser5 phosphorylation in breast cancer cells and in vitro is mediated by RSK downstream of the ERK/MAPK pathway.
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.
authors.affiliation: *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.
authors.forename: Maiti J
authors.initials: MJ
authors.lastname: Lommel
authors.affiliation: *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.
authors.forename: Panuwat
authors.initials: P
authors.lastname: Trairatphisan
authors.affiliation: *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.
authors.forename: Karoline
authors.initials: K
authors.lastname: Gäbler
authors.affiliation: *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.
authors.forename: Christina
authors.initials: C
authors.lastname: Laurini
authors.affiliation: *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.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Muller
authors.affiliation: *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.
authors.forename: Tony
authors.initials: T
authors.lastname: Kaoma
authors.affiliation: *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.
authors.forename: Laurent
authors.initials: L
authors.lastname: Vallar
authors.affiliation: *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.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sauter
authors.affiliation: *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.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Schaffner-Reckinger
mesh_terms: D000199:Actins / Q000378:metabolism; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D061986:MCF-7 Cells; D008562:Membrane Glycoproteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D012270:Ribosomes / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism
chemical_list: D000199:Actins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D051640:Small-Conductance Calcium-Activated Potassium Channels; C026742:plastin; D012694:Serine; D020928:Mitogen-Activated Protein Kinases
keywords: actin cytoskeleton; invasion; migration; signal transduction