Identification of the p16-Arc Subunit of the Arp 2/3 Complex as a Substrate of MAPK-activated Protein Kinase 2 by Proteomic Analysis

• Published in: The Journal of biological chemistry 2003-09, Vol.278 (38), p.36410-36417
• Main Authors: Singh, Saurabh, Powell, David W., Rane, Madhavi J., Millard, Tom H., Trent, John O., Pierce, William M., Klein, Jon B., Machesky, Laura M., McLeish, Kenneth R.
• Format: Article
• Language: English
• Subjects: actin; Actin-Related Protein 2; Actin-Related Protein 3; Actins - metabolism; Amino Acid Sequence; Cytoskeletal Proteins - chemistry; Cytoskeleton - metabolism; Electrophoresis, Gel, Two-Dimensional; Glutathione Transferase - metabolism; Humans; Intracellular Signaling Peptides and Proteins; Mass Spectrometry; Microfilament Proteins - chemistry; Microfilament Proteins - metabolism; Mitogen-Activated Protein Kinases - metabolism; Models, Molecular; Molecular Sequence Data; Mutation; Neutrophils - chemistry; Neutrophils - enzymology; Neutrophils - metabolism; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein Binding; Protein Conformation; Protein Isoforms; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases - chemistry; Protein-Serine-Threonine Kinases - metabolism; Serine - chemistry; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Substrate Specificity; Trypsin - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M306428200

The p38 MAPK pathway regulates multiple neutrophil functional responses via activation of the serine-threonine kinase MAPK-activated protein kinase 2 (MAPKAPK2). To identify substrates of MAPKAPK2 that mediate these responses, a proteomic approach was used in which in vitro phosphorylation of neutrophil lysates by exogenously added active recombinant MAPKAPK2 was followed by protein separation using two-dimensional electrophoresis. Peptide mass fingerprinting of peptides defined by MALDI-MS was then utilized to identify phosphorylated proteins detected by autoradiography. Six candidate substrates were identified, including the p16 subunit of the seven-member Arp2/3 complex (p16-Arc). In vitro studies confirmed that MAPKAPK2 interacts with and phosphorylates the A isoform, but not the B isoform, of p16-Arc with a stoichiometry of 0.6 to 0.7. MAPKAPK2 also phosphorylated p16-Arc in intact Arp2/3 complexes precipitated from neutrophil lysates. Mutation of serine-77 to alanine on the A isoform prevented phosphorylation by MAPKAPK2. The ability of MAPKAPK2 to phosphorylate one isoform of p16-Arc suggests a possible mechanism by which the p38 MAPK cascade regulates remodeling of the actin cytoskeleton.