Investigating the role of extracellular vesicles and unconventional protein secretion in the pathogenesis and spreading of aggregate-prone proteins in neurodegenerative diseases

Cell-to-cell communication by extracellular vesicles (EVs) is a growing field of investigation in basic cell biology research, biomarker discovery and therapeutic drug delivery. Our lab is investigating how different cargoes are loaded into EVs and the pathways that regulate EV biogenesis, release and uptake.  There are various chaperone proteins within the cell that aid the sorting of cargoes into EVs.  We are particularly interested in the aggregate-prone proteins that are associated with different neurodegenerative diseases (e.g. alpha-synuclein, SOD1, TDP-43, tau and huntingtin) and have shown that these proteins can be loaded into EVs and secreted from cells. We have recently identified that members of the small heat shock protein (sHSP) family can interact with various aggregate-prone proteins to facilitate their loading into EVs and their intercellular spreading.  In particular, we have demonstrated that one of the sHSP family, HSPB1, can interact with the autophagy cargo receptor p62/SQSTM1 to modulate its unconventional secretion by EVs. In cells expressing mutant huntingtin (the aggregate-prone protein associated with Huntington’s disease), these HSPB1-loaded EVs are capable of inducing the spreading of mutant huntingtin to non-expressing cells. Importantly, these findings reveal a novel mechanism for the spreading and seeding of protein aggregates, which may have wider implications for and impact the pathobiological mechanisms underlying other neurodegenerative disorders. In addition, we have identified several signalling pathways and regulatory proteins that are essential for the formation of mutant huntingtin-carrying EVs. 

This project will use a range of cell-based and in vivo assays to investigate how such signalling proteins regulate the interplay between autophagy and unconventional secretion and determine how this affects the accumulation and spreading of neurodegenerative disease-causing proteins. The first part of the project will involve over-expression and knockdown of these signalling proteins in vitro (in cell-based assays), where a range of biochemical and microscopy techniques will be deployed to look at protein interactions, localisation and spreading of these proteins. These findings will be then validated in vivo using a combination of zebrafish fluorescent reporter lines and neurodegenerative disease models. Finally, by using genetic and pharmacological activation and inhibition of signalling pathways, we will monitor EVs in vivo and characterise how perturbation of unconventional secretion can impact the disease progression.