Novel interactions and functions of the Adenomatous polyposis coli protein

Abstract

Mutations of the Adenomatous polyposis coli (APC) gene are a frequent and early event in the development of sporadic colorectal cancer and also form the genetic basis of familial adenomatous polyposis. APC is an established regulator of the cytoskeleton, however, the tumour suppressive function of APC has been mainly attributed to its role in Wnt signalling where it limits b-catenin levels in the absence of wnt ligands.

The aim of this project was the identification of additional proteins that bind to and are regulated by APC. I applied an untargeted global approach using immunoprecipitation of endogenous, non-tagged APC-containing protein complexes combined with mass spectrometry to identify novel APC interactors. Additionally, using mass spectrometry I measured protein levels after depleting APC and/or b-catenin, in order to identify the APC-regulated b-catenin-independent proteome.

I identified 182 APC-interacting proteins, most of which are novel. The obtained APC interactome was enriched for GO cellular component terms characteristic for epithelial cells, illustrating the importance of APC for epithelial function. Moreover, I identified many proteins that changed in abundance in the absence of APC, independently of b-catenin. Importantly, several of these were previously shown to be misregulated in human colorectal tumours. I further focused my studies on Misshapen/NIK-related kinase 1 (MINK1) which I identified and validated as a novel interactor of APC. I could show that APC depletion leads to an increase in MINK1 protein levels, that this effect is b-catenin-independent and furthermore mediated post-transcriptionally. My preliminary results suggest, that elevated MINK1 positively affects cell adhesion and additionally implicate MINK1 in spindle orientation via the phosphorylation of ERM proteins.

Date of Award	2016
Original language	English
Awarding Institution	University of Dundee
Sponsors	Cancer Research UK
Supervisor	Inke Nathke (Supervisor)