title: Naamidine A intensifies the phosphotransferase activity of extracellular signal-regulated kinases causing A-431 cells to arrest in G1.
abstract: The binding of epidermal growth factor to its receptor activates the mitogen-activated protein kinase pathway. This pathway has been identified as a vital link between membrane-bound Ras and nuclear events and, therefore, is a potential target for chemotherapeutic drugs. We reported previously that naamidine A (NA), an alkaloid from the calcareous sponge Leucetta chagosensis, potently inhibited epidermal growth factor-stimulated DNA synthesis. In this current study, we demonstrate that in addition to its antimitogenic effects (complete inhibition of DNA synthesis at 0.78 micro M in A-431 cells after 30 h), NA at 1.56 micro M caused cells to arrest in the G(1) phase of the cell cycle. In vitro kinase, in-gel kinase, and Western blotting experiments demonstrate that extracellular signal-regulated kinase (ERK) 1 and ERK2 are primary molecular targets for NA in A-431 cells. Treatment with NA at concentrations between 0.78 and 3.13 micro M produces changes in the phosphorylation states of the ERKs, and strongly induces the phosphotransferase activity of the ERK enzymes. Our data indicate that treatment with NA generates a robust ERK signal. NA is the first small molecule reported to cause this effect on the ERK kinases and consequent G(1) cell cycle arrest.
authors.affiliation: Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112-9453, USA.
authors.forename: Robyn D
authors.initials: RD
authors.lastname: James
authors.forename: David A
authors.initials: DA
authors.lastname: Jones
authors.forename: William
authors.initials: W
authors.lastname: Aalbersberg
authors.forename: Chris M
authors.initials: CM
authors.lastname: Ireland
mesh_terms: D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
chemical_list: D007093:Imidazoles; C114816:naamidine A; D020928:Mitogen-Activated Protein Kinases