Characterising the role of Valosin Containing Protein (VCP) in autophagy and cell differentiation.

Budnik-Zawilska, Milka (2015) Characterising the role of Valosin Containing Protein (VCP) in autophagy and cell differentiation. Doctoral thesis, University of East Anglia.

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Valosin containing protein (VCP)/p97 is a hexameric ATPase of the AAA family, which regulates a wide array of essential cellular processes. Dominant mutations in the N-domain of the VCP give rise to the complex disease syndrome known as Inclusion body myopathy with Paget disease of the bone and frontotemporal dementia (IBMPFD). VCP plays a key role in the ubiquitin-proteasome dependent protein degradation although mutations in VCP seem to result in a late stage autophagy defect. Osteoclast precursors containing VCP mutations are hyper-responsive to RANKL and M-CSF treatment. This suggests that under normal homeostasis VCP plays an important role in regulating the response of osteoclasts to bone microenvironment. However, the mechanisms by which VCP mutations stimulate osteoclast differentiation in Paget disease of the bone (PDB) are not completely understood.
To gain insight into disease phenotype associated with VCP mutations I examined the role of VCP in autophagy and the role of autophagy on osteoclastogenesis. I have shown that VCP co-localises with p62 and LC3 at the subcellular level in cells undergoing autophagy and that VCP co-immunoprecipitates with p62 in the autophagy-dependant manner. I have also examined the stability of VCP in the cell and shown that p62 has a role in stabilising the VCP protein and that the mutant protomers seem to be less stable than the normal VCP protomers. Initiation of autophagy in RAW264.7 cells in the presence of RANKL resulted in marked reduction in osteoclast formation, regardless of the time point at which the treatment begun. I also found that RANKL and TNFα induced NFκB activation is increased (in an autophagy dependent manner) in macrophages from the heterozygous VCP mouse compared to normal macrophages.
These data together with the already existing knowledge on VCP, and the link with PDB, suggest that modulation of the autophagy pathway by VCP may represent a major regulator of bone remodelling and maintenance. Autophagy has direct effect on the fate of osteoclast progenitor cells thus regulation of osteoclastogenesis is a key process underlying the pathogenesis of PDB. This work acts to further our understanding of the pathogenic mechanism of VCP-related disease and will facilitate the search for modifiers of the disease phenotype.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Nicola Veasy
Date Deposited: 27 Apr 2016 13:17
Last Modified: 27 Apr 2016 13:17

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