Understanding the role of Commander super assembly in endosomal cargo sorting and transport

Abstract

Cell surface protein levels change in response to alterations in the cellular environment. To regulate the cell surface proteome, integral membrane proteins and their associated ligands, collectively called ‘cargos’, are internalised from the surface. These cargos are either directed to degradation in lysosomes or recycled back to the plasma membrane through early and recycling endosomes. The recycling process relies on multiprotein systems such as Retromer, Retriever, and the CCC and WASH complexes. The heterotrimeric Retriever and heterododecameric CCC sub-complexes and an additional protein, DENND10, associate to form the 16-subunit Commander super-assembly. Although essential for recycling of integrins and lipoprotein receptors, the structure of Commander is unknown, and how it functions is poorly understood.
In this thesis, I have combined biochemical approaches, AlphaFold modelling and structure-guided mutagenesis with quantitative proteomics and cell biology validation to elucidate key interactions within each subcomplex that mediate Commander assembly and the significance of specific association for functional endosomal cargo recycling. This includes dissecting how causative mutations in Ritscher-Schinzel syndrome (RSS), a developmental condition displaying cardiac defects, cerebellar hypoplasia, and cranial dysmorphism, perturbs the overall assembly of Commander. Through interactome analysis of the core structural components of the CCC complex, I have identified and characterised various accessory proteins.
Collectively, these findings offer novel insights into the interplay between the Commander assembly and its functional role in endosomal cargo sorting.

Date of Award	17 Mar 2026
Original language	English
Awarding Institution	University of Bristol
Supervisor	Pete J Cullen (Supervisor) & Mark P Dodding (Supervisor)