Use this URL to cite or link to this record in EThOS:
Title: Linking tumour susceptibility ESCRT proteins and epithelial cell polarity
Author: Fish, Laura Pamela
ISNI:       0000 0004 2725 9653
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
The ESCRT machinery has a well established role within the endocytic pathway. Studies conducted in Drosophila have identified ESCRT proteins as important regulators of epithelial cell polarity and growth. Consequently ESCRTs have been classified as potential tumour suppressors. Alterations in the expression of various ESCRT components have been observed in human cancers. However, the possible link between ESCRT proteins, mammalian epithelial cell polarity and tumourigenesis has not been investigated. This thesis demonstrates for the first time that the ESCRT-I protein, Tsg101, is required for maintenance of mammalian epithelial cell organisation and polarity. siRNA knockdown of Tsg101 in the human Caco-2 cell line results in the formation of a multilayered epithelium with compromised apicobasal polarity. In addition, Tsg101 depletion impairs differentiation of the epithelial sheet and formation of polarised 3D Caco-2 cysts. Depletion of Tsg101 also results in intracellular accumulation of the tight junction protein, claudin-1. This is shown to be constitutively endocytosed and recycled in Caco-2 epithelial monolayers, suggesting that ESCRT-I is required for claudin-1 recycling to tight junctions. Tsg101 knockdown also impairs epithelial barrier formation and enhances Caco-2 migratory ability. This suggests that tight junction integrity is impaired and may contribute to the loss of Caco-2 cell organisation and polarity observed upon Tsg101 depletion. Finally, Tsg101 depleted Caco-2 cells appear to overproliferate, forming multilayered regions of the epithelial sheet. However, multilayered cells are eventually eliminated via apoptosis. Preliminary results suggest that inhibition of this apoptotic response enhances the aberrant epithelial phenotype, suggesting that the ability to evade apoptosis may be an important factor in determining the tumourigenic potential of ESCRT-I depletion. Therefore, results presented in this thesis suggest that the role of ESCRT-I as a tumour suppressor is conserved from Drosophila to mammals.
Supervisor: Whitley, Paul Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: ESCRT ; epithelial ; endocytosis ; cancer ; polarity