Molekularer Mechanismus der axonalen Schädigung bei neuroinflammatorischen Erkrankungen des zentralen Nervensystems
Zusammenfassung der Projektergebnisse
Intracellular aggregation of the microtubule associated protein tau is the major component of neurofibrillary tangles in Alzheimer’s disease and other neurodegenerative tauopathies. The exact molecular mechanism of tau aggregation is not known. Genetic mutations of tau and extracellular deposits of amyloid-beta peptide have been shown to facilitate aggregation of tau. Microglia cell activation precedes the formation of neurofibrillary tangles and loss of synapses. To analyze whether microglial inflammatory mediators have any effects on aggregation of tau in neurons, we performed fluorescence lifetime-based Förster resonance energy transfer (FRET) analysis of cultured primary neurons transfected with the 441 amino acid long human tau tagged to the green fluorescent protein variants Citrine (tau-Citrine) and Cerulean (tau-Cerulean). Primary neurons cotransfected with tau-Citrine and tau-Cerulean were analyzed by fluorescence lifetime imaging (FLIM) to detect any FRET signal on the subcellular level reflecting aggregation or accumulation of tau on a nanometer scale. Aggregation of tau-Citrine and tau-Cerulean co-transfected in primary neurons was only detected in a minority of untreated cells. Coculture of co-transfected neurons with pre-activated microglia resulted in aggregation of tau-Citrine and tau-Cerulean in neurites. Furthermore, treatment of neurons with tumor necrosis factor-alpha (TNF-alpha) increased the number of neurites showing aggregation of tau-Citrine and tau-Cerulean. The data demonstrate that activated microglia and the inflammatory mediator TNF-alpha, prevalent in degenerative brain diseases, can induce aggregation of tau and might be involved in the first steps of neurofibrillary tangle formation. Furthermore, the FRET-based assay system is suited to screen and validate compounds designed to prevent aggregation of tau.
Projektbezogene Publikationen (Auswahl)
- Biber K., Neumann H., Inoue K., Boddeke H. Neuronal On and Off signals control microglial. (2007). Trends Neurosci. 2007 Nov;30(11):596-602. Epub 2007 Oct 24.
- Breakdown of axonal synaptic vesicle precursor transport by microglial nitric oxide. Stagi M., Dittrich P., Frank N., Iliev A., Schwille P and Neumann H. J. Neurosci., 25(2): 352-62 (2005).
- Iliev, A., Stringaris, A.K., Nau, R. and Neumann,H. Neuronal injury mediated via stimulation of microglial toll-like receptor-9 (TLR9). FASEB J. 18, 412-414, (2004).
- Neumann H. (2004). Cellular and molecular mechanisms: Inflammation. Chapter 9 in Neuroprotection. Models, Mechanisms and Therapy. WILEY-VCH.Ed. M. Bähr. 169- 186.
- Stagi M., Gorlovoy P., Larionov S., Takahashi K. and Neumann H. Unloading kinesin transported axonal cargoes from the tubulin track via the inflammatory c-Jun Nterminal kinase pathway. FASEB J. 20(14):2573-5;[Epub ahead of print:2006 Oct 26]. (2006).
