The interplay between neurodegeneration-linked RNA-binding proteins and the nuclear transport machinery

• Applicants: Professorin Dr. Dorothee Dormann; Professor Dr. Ralph Kehlenbach
• Subject Area: Biochemistry ; Cell Biology
• Term: since 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264253189

The nuclear RNA-binding proteins FUS and TDP-43 play prominent roles in neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) or frontotemporal dementia (FTD). Mutations in FUS or TDP-43 cause familial forms of ALS, and both proteins relocalize to the cytoplasm and form insoluble cytoplasmic aggregates in neurons and glial cells of diseased brain regions. There is ample evidence that defects in nucleocytoplasmic transport and aberrant phase separation underlie the relocalization of FUS and TDP-43 from the nucleus into cytoplasmic aggregates. For a better understanding of the molecular mechanisms that contribute to ALS and related neurodegenerative diseases, it will be critical to unravel the details of nucleocytoplasmic transport of FUS and TDP-43, as well as the parameters that affect their phase separation and cytoplasmic aggregation.For FUS, the Dormann lab contributed substantially to the elucidation of such mechanisms, also in collaboration with the Kehlenbach lab. We have now joined forces and plan to use our expertise on RNA-binding proteins and nucleocytoplasmic transport to untangle the complex interplay between these disease-linked proteins and the nuclear transport machinery in neuronal and non-neuronal cells. In particular, we will focus on nuclear transport receptors and nucleoporins and their role in the regulation of TDP-43 and FUS import and phase separation. Our first goal is to characterize the interactions of TDP-43 with different soluble transport receptors. We will then analyze the capacity of transport receptors to prevent phase separation and aggregation of TDP-43 and to mediate its nuclear import. Our second goal is to understand the role of different nucleoporins in nucleocytoplasmic transport of FUS and TDP-43 and, possibly related to transport, in the regulation of phase separation of the two RNA-binding proteins and the formation of cytoplasmic aggregates. Last, we seek to examine nuclear transport receptors and nucleoporins that turn out to be relevant for TDP-43/FUS import or phase separation regulation in post mortem brains of FTD and ALS patients. The project will combine biochemical in vitro experiments and cell biological analyses in human cells, taking advantage of a large repertoire of reagents and techniques established in both the Dormann and the Kehlenbach labs.Together, this in-depth analysis of soluble (nuclear transport receptors) and rather stationary (nucleoporins) factors that directly or indirectly interact with FUS and TDP-43 will enable us to unravel how both proteins are imported into the nucleus under physiological conditions and how their phase separation and aggregation is regulated. This will allow us to understand how the two proteins behave when certain transport factors or their interactions with these factors are disturbed in disease or during ageing. Thus, we expect that our basic research will contribute to a better understanding of the ALS/FTD pathomechanism.

• DFG Programme: Research Grants