title: Phosphorylation on Ser5 increases the F-actin-binding activity of L-plastin and promotes its targeting to sites of actin assembly in cells.
abstract: L-plastin, a malignant transformation-associated protein, is a member of a large family of actin filament cross-linkers. Here, we analysed how phosphorylation of L-plastin on Ser5 of the headpiece domain regulates its intracellular distribution and its interaction with F-actin in transfected cells and in in vitro assays. Phosphorylated wild-type L-plastin localised to the actin cytoskeleton in transfected Vero cells. Ser5Ala substitution reduced the capacity of L-plastin to localise with peripheral actin-rich membrane protrusions. Conversely, a Ser5Glu variant mimicking a constitutively phosphorylated state, accumulated in actin-rich regions and promoted the formation of F-actin microspikes in two cell lines. Similar to phosphorylated wild-type L-plastin, this variant remained associated with cellular F-actin in detergent-treated cells, whereas the Ser5Ala variant was almost completely extracted. When compared with non-phosphorylated protein, phosphorylated L-plastin and the Ser5Glu variant bound F-actin more efficiently in an in vitro assay. Importantly, expression of L-plastin elicited collagen invasion in HEK293T cells, in a manner dependent on Ser5 phosphorylation. Based on our findings, we propose that conversely to other calponin homology (CH)-domain family members, phosphorylation of L-plastin switches the protein from a low-activity to a high-activity state. Phosphorylated L-plastin might act as an integrator of signals controlling the assembly of the actin cytoskeleton and cell motility in a 3D-space.
authors.affiliation: Laboratory for Molecular Biology, Genomics and Modelling, Public Research Centre for Health (CRP-Santé), 84 Val Fleuri, 1526 Luxembourg.
authors.forename: Bassam
authors.initials: B
authors.lastname: Janji
authors.forename: Adeline
authors.initials: A
authors.lastname: Giganti
authors.forename: Veerle
authors.initials: V
authors.lastname: De Corte
authors.forename: Marie
authors.initials: M
authors.lastname: Catillon
authors.forename: Erik
authors.initials: E
authors.lastname: Bruyneel
authors.forename: Delphine
authors.initials: D
authors.lastname: Lentz
authors.forename: Julie
authors.initials: J
authors.lastname: Plastino
authors.forename: Jan
authors.initials: J
authors.lastname: Gettemans
authors.forename: Evelyne
authors.initials: E
authors.lastname: Friederich
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011485:Protein Binding; D012694:Serine / Q000378:metabolism*
chemical_list: D000199:Actins; C047262:LCP1 protein, human; D008840:Microfilament Proteins; D012694:Serine