title: Plk1 regulates MEK1/2 and proliferation in airway smooth muscle cells.
abstract: BACKGROUND
  Polo-like kinase 1 (Plk1) is a serine/threonine protein kinase that has been implicated in the regulation of mitosis. In addition, the activation of mitogen-activated protein kinase (MAPK) is a key event in the early stage of the growth factor response. The role of Plk1 in MAPK phosphorylation in cells has not been investigated.
  
  
  METHODS
  Immunoblot analysis was used to evaluate Plk1 and MAPK phosphorylation in cells upon stimulation with platelet-derived growth factor (PDGF). We also generated stable Plk1 knockdown (KD) cells to assess the role of Plk1 in MAPK activation and cell proliferation. Furthermore, we used a non-phosphorylatable Plk1 mutant to determine the function of Plk1 phosphorylation in these processes.
  
  
  RESULTS
  Treatment with PDGF increased Plk1 phosphorylation at Thr-210 (an indication of Plk1 activation) in human airway smooth muscle cells. Plk1 KD attenuated the PDGF-induced phosphorylation of MEK1/2 and ERK1/2 as well as cell proliferation. However, phosphorylation of Raf-1 and AKT upon stimulation with PDGF was not reduced in Plk1 KD cells. Furthermore, the expression of T210A Plk1 (alanine substitution at Thr-210) inhibited the PDGF-stimulated MEK1/2 phosphorylation, ERK1/2 phosphorylation and cell proliferation.
  
  
  CONCLUSIONS
  Together, these findings suggest that Plk1 is activated upon growth factor stimulation, which may control the activation of MEK1/2 and ERK1/2, and smooth muscle cell proliferation.
authors.affiliation: The Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA. jiangs@mail.amc.edu.
authors.forename: Sixin
authors.initials: S
authors.lastname: Jiang
authors.affiliation: The Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA. tangd@mail.amc.edu.
authors.forename: Dale D
authors.initials: DD
authors.lastname: Tang
mesh_terms: D001980:Bronchi / Q000166:cytology / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology*; D049109:Cell Proliferation / Q000502:physiology*; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000502:physiology*; D048370:MAP Kinase Kinase 2 / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D014132:Trachea / Q000166:cytology / Q000502:physiology; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1; C482128:MAP2K2 protein, human; C482125:MAP2K1 protein, human