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Title: Localisation of MT1-MMP to motility-associated structures
Author: Woskowicz, Anna
ISNI:       0000 0004 2703 7073
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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MT1-MMP is a crucial enzyme for cellular invasion in tissues, and its polarised cell surface localisation is thought to be an important regulatory mechanism. In this thesis, the mechanisms regulating localisation of MT1-MMP to motility-associated structures were investigated. Using a series of MT1-MMP domain deletion mutants, it was found that an eight amino acid region in the catalytic domain called the “MT-Loop” is involved in localisation of the enzyme to matrix attachment sites. A previously described mechanism by which MT1-MMP localises to lamellipodia is association with CD44. Interestingly, knockdown of the CD44 in HT-1080 cells increased MT1-MMP localisation to the matrix attachment sites, whereas CD44 overexpression in COS-7 cells decreased this localisation. These results indicate that CD44-mediated localisation to lamellipodia may compete with the localisation to the matrix attachment sites. One of the previously reported mechanisms localising MT1-MMP to the matrix attachment sites is by targeting the enzyme to cortactin-mediated invadopodia structures. However, silencing of the cortactin gene in HT-1080 cells unexpectedly enhanced this localisation, suggesting that invadopodia may not be required. For MT1-MMP to appear on the cell surface, the newly expressed molecules need to be trafficked from the trans-Golgi network to the plasma membrane by kinesin motor proteins (KIFs). 17 KIFs were tested for their involvement in the intracellular trafficking of MT1-MMP-containing vesicles. Silencing of the KIF3A or KIF13A genes markedly decreased MT1-MMP-dependent gelatin and collagen film degradation, whereas silencing of the KIF9 and KIF1C genes enhanced degradation of the underlying matrix. These and other data presented in this thesis suggest that KIF3A, KIF13A, KIF9 and KIF1C may be involved in vesicle trafficking of MT1-MMP to different areas of the plasma membrane and regulate spatial localisation of the enzyme. Taken together, these findings indicate that polarised cell surface localisation of MT1-MMP is regulated by multiple mechanisms, which may be important for the enzyme to promote cellular invasion in different microenvironments.
Supervisor: Itoh, Yoshifumi Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral