Functional protein disorder in intracellular transport

Project Summary The complex organization. A human cell efficiently yet correctly distributes intracellular content detailed understanding of the transport mechanism is vital to understand despite its large size and neurodevelopmental and neurodegenerative pathologies. Dedicated kinesin and dynein motor protein complexes walk along microtubules for directional transport of cargoes such as organelles and vesicles, kinetochore, or ribonucleoproteins. involved i structura sufficient Many functionally relevant segments of proteins n this transport are structurally disordered regions (IDRs) such that static average l models provided by cryoEM or artificial intelligence-based structure prediction are not to understand the protein function.Our overarching mission is to tap into unexplored aspects of our understanding of the structure/function relationships in cargo transport in human cells. In this proposal, we ask: spectrum? 1) How can a single cytoplasmic dynein cover its entire functional There is only one major form of cytoplasmic dynein. Itsspecificities are partly due to a variety of cargo-specific motor adaptors, all of which contain IDRs, and the regulatory role of phosphorylation. Dyneinmis-regulation has been implicated in various nervous system disorders and colon cancer. We will reveal the mechanistic basis and functional implications of dynein specificity factors with a special focus on the dynein light intermediate chain (LIC), another IDR. We will also elucidate the role of the cell regulator Pin1, shown to have high interdomain flexibility, in interactions between LIC and the dynein adaptors. Olduvai 2) How does kinesin KIF5A regulation by protein impact human brain development? Olduvai domains are encoded by Neuroblastoma Breaking Point Family proteins and show the largest human-specific increase in copy number of any protein coding region in the genome. This increase is linked to brain size growth, but also to schizophrenia and autism. To date, the molecular mechanisms underlying these functions are entirely unknown. We will show how Olduvai domains, while being IDRs, act through modulation of kinesin KIF5A-driven transport, which occurs predominantly in neurons. For these studies, our tools are nuclear magnetic resonance (NMR), uniquely suited to study IDRs, supplemented with other biophysical methods to probe structure, dynamics, and interactions of proteins involved in transport, and in vitro motility and cell-based assays to study resulting functions. We will build on our 20+ years of NMR expertise, previous work on LIC- adaptor interaction and on allostery in Pin1, and foundational work on Olduvai domains. We anticipate that our work will inspire new questions about regulation of dynein transport and establish the molecular link between intracellular transport, Olduvai copy surge and brain disease.