Molecular differences between the ‘apparently homologous’ intrinsically disordered FCHO1 and FCHO2 proteins in clathrin-mediated endocytosis

• Applicant: Dr. Sigrid Milles
• Subject Area: Structural Biology ; Biophysics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564098474

Intrinsically disordered regions (IDRs) do not possess a stable three dimensional structure and play a pivotal role in cellular processes requiring dynamic molecular interactions, such as clathrin-mediated endocytosis. This process involves the selection and sorting of cargo to be taken up into the cell and the assembly of the endocytic machinery. Among the earliest proteins to arrive at the membrane to start the endocytic uptake process are F-BAR domain only (FCHO) proteins, which initiate this eukaryotic uptake mechanism. Two closely related FCHO variants, FCHO1 and FCHO2, share a similar domain architecture but exhibit distinct functional characteristics, raising intriguing questions about their roles and the underlying molecular basis for their differences. I hypothesize that the functional specificity of FCHO1 and FCHO2 resides in their IDRs, which connect their folded domains and may encode distinct molecular properties. This project employs integrated nuclear magnetic resonance (NMR), single-molecule fluorescence spectroscopy, and computational modelling, to investigate the conformational dynamics and interactions of these proteins. Ultimately, the findings will be validated in a cellular context, providing insights into the broader functional significance of IDRs in endocytosis and establishing a framework for exploring 'structure-function' relationships in disordered regions across various biological systems.

• DFG Programme: Research Grants