Regulation of beta-amyloid precursor protein expression by brain-derived neurotrophic factor involves activation of both the Ras and phosphatidylinositide 3-kinase signalling pathways.
Brain-derived neurotrophic factor (BDNF) stimulates beta-amyloid precursor protein (APP) promoter activity by a Ras-dependent mechanism in TrkB-expressing SH-SY5Y cells. To determine the signalling pathways involved in the BDNF-induced response, we have analysed the ability of TrkB mutated forms to mediate promoter stimulation. Brain-derived neurotrophic factor causes a significant induction of promoter activity and mutation K540R in the active site of TrkB completely abolishes the neurotrophin-induced response. A substitution of the Y484 residue by phenylalanine, which blocks binding of Shc, reduces the activation of APP promoter by BDNF by approximately 50% whereas mutation Y785P, which blocks binding of phospholipase C gamma, does not affect the response. In addition, the phosphatidylinositide 3-kinase (PI3K)-specific inhibitors wortmannin and LY294002 reduced BDNF-induced activation. In agreement with a participation of both Ras/MAPK- and PI3K/Akt-mediated mechanisms, transient expression of constitutive active forms of Ras, PI3K and other components of both signalling pathways led to a significant increase of APP promoter activity. Furthermore, the stimulation of the APP promoter by BDNF was completely precluded by expression of dominant-negative forms of Ras and PI3K effectors. Taken together, our results suggest that simultaneous activation of at least two signalling pathways, Ras/MAPK and PI3K/Akt, is necessary to mediate a full activation of the APP promoter by BDNF.
Ruiz-León
Yolanda
Y
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Pascual
Angel
A
D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D015153:Blotting, Western / Q000379:methods; D019208:Brain-Derived Neurotrophic Factor / Q000502:physiology*; D045744:Cell Line, Tumor; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D009154:Mutation / Q000235:genetics; D009447:Neuroblastoma; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011233:Precipitin Tests / Q000379:methods; D011401:Promoter Regions, Genetic; D020813:Receptor, trkB / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism*
D016564:Amyloid beta-Protein Precursor; D019208:Brain-Derived Neurotrophic Factor; D004791:Enzyme Inhibitors; D015500:Chloramphenicol O-Acetyltransferase; D019869:Phosphatidylinositol 3-Kinases; D020813:Receptor, trkB; D018631:ras Proteins