Molecular characterisation of a novel vipar interacting protein in health and disease

Banushi, Blerida (2014). Molecular characterisation of a novel vipar interacting protein in health and disease. University of Birmingham. Ph.D.

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Arthrogryposis, Renal dysfunction, and Cholestasis (ARC) syndrome is a multisystem disorder caused by mutations in genes encoding two proteins VPS33B or VIPAR, which appear to be critical regulators of cell polarity. VPS33B and VIPAR may function as part of a multi-protein complex that interacts with an active form of RAB11A and is involved in the transcriptional regulation of E-cadherin. VPS33B and VIPAR are shown to interact at a protein level forming a stable binary complex. A novel interacting partner of VIPAR was identified, PLOD3, a posttranslational modification enzyme with lysyl hydroxylase (LH), collagen galactosyltransferase (GT), and glucosyltransferase (GGT) activities (Wang et al., 2012). In mIMCD-3 polarized cell lines VPS33B and VIPAR are involved in PLOD3 trafficking from the TGN compartment via RAB11A positive vesicles. Study of the topology of this ternary protein complex evidenced that VIPAR is a transmembrane protein with its luminal N-terminal interacting with PLOD3 and its cytosolic C-terminal being involved in the interaction with VPS33B. VPS33B/VIPAR mediates the trafficking of PLOD3 from the TGN to collagen carrier structures where the binding of PLOD3 with collagen takes place. The PLOD3-collagen binding is required for collagen trafficking and an abnormal accumulation of intracellular collagen, associated with failure in PLOD3 delivery to collagen, is observed in Vipar knockdown mIMCD-3 cells. Abnormal collagen modifications and trafficking in Vps33b/Vipar deficiency can explain the down-regulation of E-cadherin that characterises some polarized cell types in ARC and the cell model for this syndrome. These findings establish a role for VPS33B/VIPAR in the intracellular trafficking of collagen.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Colleges (2008 onwards) > College of Medical & Dental Sciences
School or Department: School of Clinical and Experimental Medicine, Department of Medical and Molecular Genetics
Funders: European Commission
Subjects: R Medicine > R Medicine (General)
R Medicine > RC Internal medicine


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