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Examination of actin and microtubule dependent APC localisations in living mammalian cells

Langford, K.J., Askham, J.M., Lee, T., Adams, A. and Morrison, E.E. (2006) Examination of actin and microtubule dependent APC localisations in living mammalian cells. BMC Cell Biology, 7 (3). ISSN 1471-2121

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Abstract

Abstract (provisional)

Background

The trafficking of the adenomatous polyposis coli (APC) tumour suppressor protein in mammalian cells is a perennially controversial topic. Immunostaining evidence for an actin-associated APC localisation at intercellular junctions has been previously presented, though live imaging of mammalian junctional APC has not been documented.

Results

Using live imaging of transfected COS-7 cells we observed intercellular junction-associated pools of GFP-APC in addition to previously documented microtubule-associated GFP-APC and a variety of minor localisations. Although both microtubule and junction-associated populations could co-exist within individual cells, they differed in their subcellular location, dynamic behaviour and sensitivity to cytoskeletal poisons. GFP-APC deletion mutant analysis indicated that a protein truncated immediately after the APC armadillo repeat domain retained the ability to localise to adhesive membranes in transfected cells. Supporting this, we also observed junctional APC immunostaining in cultures of human colorectal cancer cell line that express truncated forms of APC.

Conclusions

Our data indicate that APC can be found in two spatially separate populations at the cell periphery and these populations can co-exist in the same cell. The first localisation is highly dynamic and associated with microtubules near free edges and in cell vertices, while the second is comparatively static and is closely associated with actin at sites of cell-cell contact. Our imaging confirms that human GFP-APC possesses many of the localisations and behaviours previously seen by live imaging of Xenopus GFP-APC. However, we report the novel finding that GFP-APC puncta can remain associated with the ends of shrinking microtubules. Deletion analysis indicated that the N-terminal region of the APC protein mediated its junctional localisation, consistent with our observation that truncated APC proteins in colon cancer cell lines are still capable of localising to the cell cortex. This may have implications for the development of colorectal cancer.

Item Type: Article
Copyright, Publisher and Additional Information: © 2006 Langford et al., licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This Provisional PDF corresponds to the article as it appeared upon acceptance.
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Medicine and Health (Leeds) > Institute of Molecular Medicine (LIMM) (Leeds) > Section of Oncology and Clinical Research (Leeds)
Depositing User: Repository Officer
Date Deposited: 13 Mar 2006
Last Modified: 06 Jun 2014 21:18
Published Version: http://www.biomedcentral.com/1471-2121/7/3
Status: Published
Refereed: Yes
Identification Number: 10.1186/1471-2121-7-3
URI: http://eprints.whiterose.ac.uk/id/eprint/1063

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