title: Tyrosine phosphorylation of extracellular signal-regulated protein kinase 4 in response to growth factors.
abstract: Extracellular signal-regulated protein kinases (ERKs) are members of the mitogen-activated protein kinase family that are rapidly phosphorylated and activated in response to various extracellular stimuli, including growth factors. Of these, the ERK1 and ERK2 forms are by far the most abundant and the most studied. Much less is known about other ERK forms, including one previously designated ERK4 on the basis of its cross-reactivity with ERK1 and ERK2. We report here that ERK4 in rat PC12 pheochromocytoma cells can be immunoprecipitated by anti-ERK antiserum R2 and have used this re-agent to characterize this species further. We find that ERK4 rapidly becomes tyrosine-phosphorylated in response to nerve growth factor (NGF) and epidermal growth factor (EGF) and, to a lesser degree, in response to insulin and a permeant cyclic AMP analogue. As in the case of ERK1 and ERK2, tyrosine phosphorylation of ERK4 occurs by a ras-dependent pathway in response to NGF and EGF and shows prolonged kinetics for NGF but not EGF treatment. Recognition by multiple antisera directed against various domains of ERK1 supports classification of ERK4 within the ERK family; however, two-dimensional gel analysis clearly distinguishes ERK4 from isoforms of ERK1. These findings thus reveal an additional member of the ERK family that is responsive to growth factors and that could play a distinct role in intracellular signaling.
authors.affiliation: Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
authors.forename: X
authors.initials: X
authors.lastname: Peng
authors.forename: J M
authors.initials: JM
authors.lastname: Angelastro
authors.forename: L A
authors.initials: LA
authors.lastname: Greene
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000276:immunology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases; D005110:Extracellular Space / Q000378:metabolism*; D006133:Growth Substances / Q000494:pharmacology*; D015151:Immunoblotting; D007700:Kinetics; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009414:Nerve Growth Factors / Q000494:pharmacology; D016716:PC12 Cells; D010766:Phosphorylation; D011233:Precipitin Tests; D051381:Rats; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*; D018631:ras Proteins / Q000502:physiology
chemical_list: D000906:Antibodies; D006133:Growth Substances; D009414:Nerve Growth Factors; D014443:Tyrosine; D004815:Epidermal Growth Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C102548:Mapk4 protein, rat; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins