How are cargoes trafficked within cells with such speed and directional precision? Our research aims to address this question by using structural cell biology to uncover the molecular mechanisms of transport by microtubule-based motor proteins, with a particular focus on the formation and function of the primary cilium.
The primary cilium is a microtubule-based, antenna-like organelle present on nearly every cell in the human body. It plays a crucial role in sensing and transducing environmental signals to guide cell behaviour during development. Disruption of ciliary trafficking pathways leads to a range of severe developmental and degenerative diseases, collectively known as ciliopathies.
At the heart of ciliary assembly and functions is a transport system that traffics building blocks and signalling molecules into and out of the cilium. It employs multi-megadalton ‘IFT trains’ that transport cargoes along the ciliary microtubules under the power of kinesin-2 and dynein-2 motor proteins.
A remarkable feature of IFT is that trains reverse direction specifically at the ciliary tip, switching from kinesin- to dynein-driven motility, making IFT an excellent model for studying regulated directional transport [1,2]. We recently determined the cryo-EM structures of dynein-2 [3] and the IFT-A [1] complex, used CRISPR/Cas9 genome editing [4] to dissect their roles, and obtained molecular insight into how kinesin-2 is inhibited [5]. Together, these advances provide a foundation for determining how IFT train directionality is regulated.
The central goal of this PhD project is to determine the molecular mechanisms by which IFT trains change direction precisely at the ciliary tip.
To achieve this, the project will combine state-of-the-art techniques, including:
By integrating structural, cell and computational biology approaches, this project aims to reveal the molecular logic underlying one of the cell’s most precisely regulated transport systems, with the potential to uncover fundamental mechanisms relevant to human health and disease.
Publications
[1] IFT-A Structure Reveals Carriages for Membrane Protein Transport into Cilia (2022) Hesketh SJ, Mukhopadhyay AG, Nakamura D, Toropova K, Roberts AJ. Cell, 185(26):4971-4985
[2] Intraflagellar Transport Trains and Motors (2020) Webb S, Mukhopadhyay AG, Roberts AJ. Seminars in Cell & Developmental Biology, 107:82-90
[3] Structure of the Dynein-2 Complex and its Assembly with Intraflagellar Transport Trains (2019) Toropova K, Zalyte R, Mukhopadhyay AG, Mladenov M, Carter AP, Roberts AJ. Nature Structural & Molecular Biology, 26(9):823-829
[4] Structure and Tethering Mechanism of Dynein-2 Intermediate chains in Intraflagellar Transport (2024) Mukhopadhyay AG, Toropova K, Daly L, Wells JN, Vuolo L, Mladenov M, Seda M, Jenkins D, Stephens DJ, Roberts AJ. EMBO J 43(7):1257-1272
[5] Regulation of Kinesin-2 Motility by its β-hairpin Motif (2025) Webb S, Toropova K, Mukhopadhyay AG, Nofal SD, Roberts AJ. Nature Structural & Molecular Biology 32(8):1989-1998
Toropova group
Discovering how molecular machines perform essential cellular functions using cryo-electron microscopy / tomography and live fluorescence imaging.
Roberts group
Investigating how motor proteins generate movement and spatial organisation within living cells
Our PhD course
Doing a DPhil in Molecular Cell Biology in Health and Disease at the Dunn School is the best way to start your career.