title: Identification of myristoylated alanine-rich C kinase substrate (MARCKS) in astrocytes.
abstract: We have characterized membrane-associated substrates of Ca2+-dependent kinases in primary rat astrocytes by in vitro phosphorylation, 2-dimensional gel electrophoresis and autoradiography. The most prominent among these were three acidic, protein kinase C (PKC) substrates. These are important because they likely transduce cytokine and other neuro-immune modulatory signals mediated by PKC. We now show that one of these phosphoproteins is myristoylated alanine-rich PKC kinase substrate (MARCKS) or phosphomyristin C. The identity was corroborated by one- and 2- dimensional immunoblotting with an MARCKS-specific polyclonal antibody. Exposing primary astrocytes to phorbol 12-myristate 13-acetate stimulated phosphorylation of this protein. The level of MARCKS appeared inversely proportional to the proliferative potential of astrocytes because it was lower in spontaneously transformed as compared to passaged or confluent cells. These data are consistent with previous reports and indicate that one of three major acidic membrane-associated PKC substrates in astrocytes is MARCKS. Thus, MARCKS is likely near-proximal transducer of PKC-mediated signals in astrocytes.
authors.affiliation: Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. vitkovic@hotmail.com <vitkovic@hotmail.com>
authors.forename: Ljubisa
authors.initials: L
authors.lastname: Vitkovic
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Aloyo
authors.forename: Shigeru
authors.initials: S
authors.lastname: Maeda
authors.forename: Deborha L
authors.initials: DL
authors.lastname: Benzil
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Bressler
authors.forename: Dana C
authors.initials: DC
authors.lastname: Hilt
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D001345:Autoradiography; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D019922:GAP-43 Protein / Q000737:chemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D009457:Neuroglia / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D016207:Cytokines; D019922:GAP-43 Protein; D047908:Intracellular Signaling Peptides and Proteins; C000619712:Marcks protein, rat; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate