Biology subjects

Foster, H. E.

Publications and source records attributed to Foster, H. E..

3 recordsLinked to original sources

bioRxiv2022

The Molecular Structure of Anterograde Intraflagellar Transport Trains

Anterograde intraflagellar transport trains are essential for cilia assembly and maintenance. These trains are formed of 22 IFTA and IFTB proteins that link structural and signalling cargoes to microtubule motors for import into cilia. It remains unknown how the IFTA/B proteins are arranged into complexes and how these complexes polymerise into functional trains. Here, we use in situ cryo-electron tomography and Alphafold2 protein structure predictions to generate the first molecular model of the entire anterograde train. We show how the conformation of both IFTA and IFTB is dependent on lateral interactions with neighbouring repeats, suggesting that polymerization is required to cooperatively stabilize the complexes. The retrograde dynein motor binding site is a composite surface involving multiple IFTB repeats, ensuring that dynein can only form a strong interaction with IFTB upon train assembly. Finally, we reveal how IFTB extends two flexible tethers to maintain a connection with IFTA that can withstand the mechanical stresses present in actively beating cilia. Overall, our findings provide a framework for understanding the fundamental processes that are involved in cilia assembly.

molecular biology↗

bioRxiv2021

A cryo-ET survey of intracellular compartments within mammalian axons

The neuronal axon contains many intracellular compartments which travel between the cell body and axon tip. The nature of these cargos and the complex axonal environment through which they traverse is unclear. Here, we describe the internal components of mammalian sensory axons using cryo-electron tomography. We show that axonal endoplasmic reticulum has thin, beaded appearance and is tethered to microtubules at multiple sites. The tethers are elongated, [~] 7 nm long proteins which cluster in small groups. We survey the different membrane-bound cargos in axons, quantify their abundance and describe novel internal features including granules and broken membranes. We observe connecting density between membranes and microtubules which may correspond to motor proteins. In addition to membrane-bound organelles, we detect numerous proteinaceous compartments, including vaults and previously undescribed virus-like capsid particles. The abundance of these compartments suggests they undergo trafficking in axons. Our observations outline the physical characteristics of axonal cargo and provide a platform for identification of their constituents.

cell biology↗

bioRxiv2021

A cryo-ET study of microtubules in axons

The microtubule cytoskeleton in axons plays key roles in intracellular transport and in defining cell shape. Despite many years of study of microtubules, many questions regarding their native architecture remain unanswered. Here, we performed cryo-electron tomography of mouse dorsal root ganglion (DRG) and Drosophila melanogaster (Dm) neurons and examined their microtubule ultrastructure in situ. We found that the microtubule minus and plus ends in DRG axons are structurally similar and frequently contact nearby components. The microtubules in DRG axons maintained a 13 protofilament (pf) architecture, even close to lattice break sites. In contrast, microtubules in Dm neurons had 12 or 13 pfs and we detected sites of pf number transition. The microtubule lumen in DRG axons is filled with globular microtubule inner proteins (MIPs). Our data suggest these have a defined structure, which is surprising given they are thought to contain the disordered protein MAP6. In summary, we reveal novel morphological and structural features of microtubules in their native environment.

cell biology↗