title: Stress-dependent phosphorylation of myocardin-related transcription factor A (MRTF-A) by the p38(MAPK)/MK2 axis.
abstract: Myocardin-related transcription factor A (MRTF-A) is a known actin-regulated transcriptional coactivator of serum response factor (SRF). Stimulation of actin polymerization activates MRTF-A by releasing it from G-actin and thus allowing it to bind to and activate SRF. Here, we compared protein phosphorylation in MK2/3-deficient cells rescued or not by ectopic expression of MK2 in two independent phosphoproteomic approaches using anisomycin-treated MEF cells and LPS-stimulated mouse macrophages, respectively. Two MRTF-A sites, Ser(351) (corresponding to Ser(312) in human) and Ser(371) (Ser(333) in human), showed significantly stronger phosphorylation (12-fold and 6-fold increase) in the cells expressing MK2. MRTF-A is phosphorylated at these sites in a stress-, but not in a mitogen-induced manner, and p38(MAPK)/MK2 catalytic activities are indispensable for this phosphorylation. MK2-mediated phosphorylation of MRTF-A at Ser(312) and Ser(333) was further confirmed in an in vitro kinase assay and using the phospho-protein kinase-D (PKD)-consensus motif antibody (anti-LXRXXpS/pT), the p38(MAPK) inhibitor BIRB-796, MK2/3-deficient cells and MRTF-A phospho-site mutants. Unexpectedly, dimerization, subcellular localization and translocation, interaction with actin, SRF or SMAD3 and transactivating potential of MRTF-A seem to be unaffected by manipulating the p38(MAPK)/MK2-dependent phosphorylations. Hence, MRTF-A is stress-dependently phosphorylated by MK2 at Ser(312) and Ser(333) with so far undetected functional and physiological consequences.
authors: Department of Biochemistry, Hannover Medical School, Hannover, Germany.
authors: Natalia
authors: N
authors: Ronkina
authors: Department of Biochemistry, Hannover Medical School, Hannover, Germany.
authors: Juri
authors: J
authors: Lafera
authors: Department of Biochemistry, Hannover Medical School, Hannover, Germany.
authors: Alexey
authors: A
authors: Kotlyarov
authors: Department of Biochemistry, Hannover Medical School, Hannover, Germany.
authors: Matthias
authors: M
authors: Gaestel
mesh_terms: D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism*; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D000841:Anisomycin; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D015534:Trans-Activators; D000099190:MAP-Kinase-Activated Kinase 2; C511173:Mrtfa protein, mouse