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Björn Falkenburger Group

Cell biology of neurodegenerative diseases

Portrait Björn Falkenburger

We study movement disorders and neurodegenerative diseases on a cellular and molecular level. Parkinson's disease is characterized by aggregation of alpha-synuclein in neuronal cells of the central and peripheral nervous systems. We have found that cells can sequester such protein aggregates in aggresomes and degrade them through autophagy. We now study the molecular basis of this clearance process in order to identify new molecular targets for the development of neuroprotective therapies.

Aggregate transport

The transport of aggregates into a perinuclear aggresome is mediated by the microtubule-dynein system. Lewy bodies are likely derived from such aggresomes. We investigate the molecular components necessary for aggregate transport, in particular the molecules responsible for linking misfolded proteins to the dynein complex, and determine the rate-limiting resource for aggregate transport. We compare the transport of aggregates in neurons to transport in cell lines in order to determine the specific vulnerability of neuronal cells for protein aggregates.

Aggresome clearance

Aggregates are degraded by autophagy where pieces of cytosol are engulfed by a membrane. These autophagosomes subsequently fuse with lysosomes to degrade their content. We determine the molecular players and cellular trafficking events involved in autophagic aggregate clearance.

In previous work we could show that autolysosomal degradation of alpha-synuclein aggregates is induced by overexpression of Rab7. Several Rab proteins promote aggregate clearance, but Rab7 is of particular interest since it mediates effects of PINK, parkin and LRRK2 (mutations in these genes are associated with familial Parkinson's disease). The most important effector of Rab7 is FYCO1, which also induces aggregate clearance.

We are particularly interested in the intracellular trafficking route of autophagosomes and in the role membrane lipids play for autophagosome maturation. Also, some of the pathways involved in aggregate clearance could be involved in secretion of synuclein aggregates, which underlies the spread of pathology throughout the nervous system.

Experimental therapy

In order to further develop our previous work into a therapeutic strategy for Parkinson's disease we validate interventions found effective in cell lines in more advanced models. We test such interventions in primary mouse neurons, IPS-cell derived neurons, and in a mouse model using intracerebral injection of alpha-synuclein fibrils.

Björn Falkenburger Research: Figure
Figure: This is a cartoon view of current hypotheses about synuclein degradation and secretion. Degradation pathway (blue): Aggregates are transported towards the perinuclear region where they form aggresomes. Aggresomes are hubs for autophagy, i.e. the engulfment of aggregates by cellular membranes, leading to double-membrane vesicles. These autophagosomes can fuse with lysosomes to degrade their cargo. Formation of extracellular vesicles (red): Ectosomes are vesicles shedded from the plasma membrane. They contain cytosol and thus may include aggregates. Exosomes result from fusion of double-membrane compartments with the plasma membrane, such as multivesicular bodies and autophagosomes. Extracellular vesicles are taken up by neighbouring cells by either fusion with the plasma membrane or endocytosis. Membrane binding (green): Synuclein binding to cellular membranes is likely to impair processing through the transport - autophagy - secretion/degradation pathway.

Future Projects and Goals

Our aim is to develop disease-modifying treatments for neurologic diseases, focusing on Parkinson’s disease (PD). PD is characterized by dopamine deficiency and alpha-synuclein aggregates. Dopamine deficiency mediates PD motor symptoms and can be compensated by dopamine replacement therapy. Synuclein aggregates underlie non-motor symptoms that for the most part cannot be treated to date. One strategy is therefore to identify and target factors that limit the degradation of synuclein aggregates as laid out above.

A second strategy is to determine secondary effects of dopamine deficiency on non-dopaminergic neurons. We have identified such changes in striatal medium spiny neurons and now investigate the cell biological events that underlie these changes. We expect that preventing them can reduce dyskinesias and motor fluctuations that occur in advanced stages of PD.

Methodological and Technical Expertise

  • cellular and animal models of neurologic diseases
  • visualisation and quantification of protein aggregates
  • life cell microscopy
  • reporting and manipulating phosphoinositide lipids
  • patch clamp and MEA electrophysiology

Currently Recruiting

Björn Falkenburger is recruiting in the PhD Fall Selection 2019 (call is closed)

CV

since January 2019
Professor of Neurology / Movement disorders, Department of Neurology, TU Dresden

2014–2018
Assistant Professor (W1), Department of Neurology, RWTH Aachen University, “geschäftsführender Oberarzt” and group leader

2011–2014
Group leader and resident, Department of Neurology, RWTH Aachen University

2008–2010
Postdoctoral Scientist, Department of Physiology and Biophysics, University of Washington, Seattle

2004–2007
Group leader, Department of Neurodegeneration and Restorative Research, University of Göttingen; Resident, Department of Neurology, University of Göttingen

2003–2004
Postdoctoral Scientist and resident, Department of Neurology, University of Tübingen

1996–2002
Medical Schoool, University of Tübingen

Selected Publications

Saridaki T, Nippold M, Dinter E, Roos A, Diederichs L, Fensky L, Schulz JB, Falkenburger BH
FYCO1 mediates clearance of α-synuclein aggregates through a Rab7-dependent mechanism.
J Neurochem 146:474–492 (2018)

Falkenburger BH, Saridaki T, Dinter E
Cellular models for Parkinson’s disease.
J Neurochem 139 Suppl 1:121–130 (2016)

Falkenburger BH, Jensen JB, Dickson EJ, Suh B-CC, Hille B
Phosphoinositides: lipid regulators of membrane proteins.
J Physiol 588:3179–3185 (2010)

Opazo F, Krenz A, Heermann S, Schulz JB, Falkenburger BH
Accumulation and clearance of -synuclein aggregates demonstrated by time-lapse imaging.
J Neurochem 106:529–540 (2008)

Falkenburger BH, Barstow KL, Mintz IM
Dendrodendritic inhibition through reversal of dopamine transport.
Science 293:2465–2470 (2001)

Contact

University Hospital Carl Gustav Carus
Technische Universität
Department of Neurology
Fetscherstraße 74
01307 Dresden
Germany