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Together with other Golgi matrix components, GRASP65 contributes to the stacking of Golgi cisternae in interphase cells. During mitosis, GRASP65 is heavily phosphorylated, and in turn, cisternal stacking is inhibited leading to the breakdown of the Golgi apparatus. Here we show that GRASP65 is phosphorylated on serine 277 in interphase cells, and this is strongly enhanced in response to the addition of serum or epidermal growth factor. This is directly mediated by ERK suggesting that GRASP65 has some role in growth factor signal transduction. Phosphorylation of Ser-277 is also dramatically increased during mitosis, however this is mediated by Cdk1 and not by ERK. The microinjection of recombinant GRASP65 without N-terminal myristoylation or a peptide fragment containing Ser-277 into the cytosol of normal rat kidney cells inhibits passage through mitosis. This effect is abolished when Ser-277 is replaced with alanine suggesting the phosphorylation of Ser-277 plays an important role in cell cycle regulation. The convergence of cell cycle regulation and growth factor signals on GRASP65 Ser-277 suggests that GRASP65 may function as a signal integrator controlling the cell growth.

Original publication

DOI

10.1074/jbc.M502442200

Type

Journal article

Journal

J Biol Chem

Publication Date

17/06/2005

Volume

280

Pages

23048 - 23056

Keywords

Amino Acid Sequence, Animals, Binding Sites, CDC2 Protein Kinase, COS Cells, Cell Cycle, Cell Line, Cytosol, DNA, Complementary, Electrophoresis, Polyacrylamide Gel, Epidermal Growth Factor, Extracellular Signal-Regulated MAP Kinases, Fluorescent Antibody Technique, Indirect, Gene Expression Regulation, Golgi Apparatus, HeLa Cells, Humans, Interphase, Liver, Membrane Proteins, Microscopy, Confocal, Mitosis, Molecular Sequence Data, Mutation, Peptides, Phosphorylation, Protein Structure, Tertiary, Rats, S Phase, Serine, Signal Transduction, Time Factors