The role of RNA binding for Trim2 and Trim3 function

• Applicant: Dr. Inga Loedige
• Subject Area: Developmental Biology ; Biochemistry ; Cell Biology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389869242

Neurological disorders are one of the main challenges of an aging population and in most instances there is no cure for these disorders. Understanding their pathogenesis will certainly benefit from a more thorough understanding of the molecular mechanisms that underlie neuronal function. The complex morphology of neurons and their ability to receive and process information within sites distant from the cell body requires local protein synthesis and active transport mechanisms. RNA localization and local translation are essential for learning and memory and to maintain neuronal function. Although research over the past years has identified a large number of RNAs that localize to axon and dendrites, the molecular mechanisms of RNA transport, localization and local translation remain poorly understood.Trim2 and Trim3 are two closely related proteins that regulate axon regeneration and synaptic plasticity by yet unknown mechanisms. Trim2 deficiency or mutation causes Charcot-Marie-Tooth-Disease, an early-onset axonal neuropathy, while Trim3 has been associated with Schizophrenia. Trim2 and Trim3 belong to a conserved family of developmental regulators that are characterized by their N-terminal TRIM motif, a motif that confers ubiquitin ligase activity and their C-terminal NHL domain. Major accomplishment of my post-doctoral work was to demonstrate that the NHL domain, the signature domain of TRIM-NHL proteins, is a sequence-specific RNA binding domain and that TRIM-NHL proteins bind and regulate mRNAs to control gene expression posttranscriptional.Within this project, I want to build on these findings to elucidate how Trim2 and Trim3 control axon maintenance and synaptic plasticity. I will combine genome-wide approaches, biochemistry and cell-based assays to systematically identify their RNA targets and to determine their impact on neuronal RNA fate. The direct interaction of Trim2 and Trim3 with various motor proteins and their identification as core components of a neuronal mRNA transport granule strongly suggest a role for Trim2 and Trim3 in neuronal RNA transport. Taking advantage of the possibility to separate soma and neurites of neurons grown in culture, I will investigate how Trim2 and Trim3 contribute to RNA localization and local translation using biochemistry and genome-wide approaches. To understand if and how their ubiquitin ligase and RNA binding activities are linked, I additionally aim to identify their ubiquitinated substrates.This study will reveal insights into the complex RNA-based regulatory mechanisms that control neuronal function and will further our understanding of RNA localization and local translation, a still poorly understood process. It will also provide the first comprehensive and genome-wide analysis of TRIM-NHL protein function and will likely deliver insights into the pathogenesis of TRIM-NHL protein associated diseases, including Charcot-Marie-Tooth-Disease and Schizophrenia.

• DFG Programme: Research Grants