title: Calmodulin kinase II-dependent transactivation of PDGF receptors mediates astrocytic MMP-9 expression and cell motility induced by lipoteichoic acid.
abstract: BACKGROUND
  Lipoteichoic acid (LTA) is a component of Gram-positive bacterial cell walls, which has been found to be elevated in cerebrospinal fluid of patients suffering from meningitis. Moreover, matrix metalloproteinases (MMPs), MMP-9 especially, have been observed in patients with brain inflammatory diseases and may contribute to brain disease pathology. However, the molecular mechanisms underlying LTA-induced MMP-9 expression in brain astrocytes remain unclear.
  
  
  OBJECTIVE
  The goal of this study was to examine whether LTA-induced cell migration is mediated by calcium/calmodulin (CaM)/CaM kinase II (CaMKII)-dependent transactivation of the PDGFR pathway in rat brain astrocytes (RBA-1 cells).
  
  
  METHODS
  Expression and activity of MMP-9 induced by LTA was evaluated by zymographic, western blotting, and RT-PCR analyses. MMP-9 regulatory signaling pathways were investigated by treatment with pharmacological inhibitors or using dominant negative mutants or short hairpin RNA (shRNA) transfection, and chromatin immunoprecipitation (ChIP)-PCR and promoter activity reporter assays. Finally, we determined the cell functional changes by cell migration assay.
  
  
  RESULTS
  The data show that c-Jun/AP-1 mediates LTA-induced MMP-9 expression in RBA-1 cells. Next, we demonstrated that LTA induces MMP-9 expression via a calcium/CaM/CaMKII-dependent transactivation of PDGFR pathway. Transactivation of PDGFR led to activation of PI3K/Akt and JNK1/2 and then activated c-Jun/AP-1 signaling. Activated-c-Jun bound to the AP-1-binding site of the MMP-9 promoter, and thereby turned on transcription of MMP-9. Eventually, up-regulation of MMP-9 by LTA enhanced cell migration of astrocytes.
  
  
  CONCLUSIONS
  These results demonstrate that in RBA-1 cells, activation of c-Jun/AP-1 by a CaMKII-dependent PI3K/Akt-JNK activation mediated through transactivation of PDGFR is essential for up-regulation of MMP-9 and cell migration induced by LTA. Understanding the regulatory mechanisms underlying LTA-induced MMP-9 expression and functional changes in astrocytes may provide a new therapeutic strategy for Gram-positive bacterial infections in brain disorders.
authors.affiliation: Department of Physiology and Pharmacology, Chang Gung University, Tao-Yuan, Taiwan.
authors.forename: Hui-Hsin
authors.initials: HH
authors.lastname: Wang
authors.forename: Hsi-Lung
authors.initials: HL
authors.lastname: Hsieh
authors.forename: Chuen-Mao
authors.initials: CM
authors.lastname: Yang
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051381:Rats; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013682:Teichoic Acids / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D008070:Lipopolysaccharides; D013682:Teichoic Acids; D018808:Transcription Factor AP-1; C009900:lipoteichoic acid; D019869:Phosphatidylinositol 3-Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D048031:JNK Mitogen-Activated Protein Kinases; D020780:Matrix Metalloproteinase 9; D002118:Calcium