EPIADHESION · Regulation of cell adhesion, polarity and proliferation in mammalian epithelial celles by proteins of the discs large and crumbs group
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2005-01-01 → 2006-12-31
- EU contribution
- €285,271
- Participants
- 1
- Scheme
- EIF
Lines connect the coordinator with its partners.
Results in brief
Final Activity Report Summary - EPIADHESION (Regulation of cell adhesion, polarity and proliferation in mammalian epithelial celles by proteins of the discs large and crumbs group)
Genetic studies in Drosophila and C. elegans have identified three groups of evolutionarily conserved proteins required for the establishment of cell polarity in a variety of biological contexts: (i) Par3, Par6, aPKC (in some cases the activity of aPKC is regulated by small GTPases, such as Cdc42); (ii) Crb3 (Crumbs), PALS1 (MPP5), PATJ, which are both located predominantly apically; and (iii) Dlg1, Scribble, Lgl located mostly on the basolateral surfaces. During epithelial morphogenesis, these proteins participate in a complex network of inter-dependent interactions that define the position and functional organization of adherens junctions and tight junctions. The loss of epithelial integrity is a key feature of many human cancers and several of these proteins exhibit tumour suppressor activity; however, the biochemical pathways through which they control polarity are poorly understood. During the course of our studies, we identified a biochemical and functional link between human Dlg1 and Crb3 polarity complexes, which is mediated via the previously uncharacterised MAGUK-p55 subfamily member MPP7. MPP7 was identified by mass spectrometry as a major protein co-immunoprecipitating specifically with endogenous hDlg1 from polarised MCF7 mammary breast epithelial cell extracts and this interaction requires the L27N domain of MPP7 and the L27 domain of hDlg1. Using confocal microscopy, we showed that MPP7 localises at the lateral site in polarised epithelial cells and partially colocalises with markers for adherens and tight junctions. Importantly, MPP7 targets via its interaction with hDlg1 to the lateral surface in epithelial cells, as in hDlg1-depleted cells, MPP7 fails to localize to the plasma membrane. In addition, the transmembrane protein Crb3 can recruit wild-type MPP7, but not MPP7 with a deleted SH3-HOOK domain, to the cell membrane and this relocalisation is mediated via a physical interaction between MPP7 and PALS1. Interference with MPP7 function using retroviral shRNA results in a delay in the formation of functional tight junctions as judged by transepithelial electrical resistance measurements. These data identify a new biochemical link between polarity protein complexes that plays an important role in epithelial polarity and tight junction integrity.
Data: CORDIS, © European Union
Project objective
Epithelial tumours are characterized by a loss of their polarized cellular architecture, which is correlated with less adhesive and more migratory properties of the tumour cell. Genetic analysis in Drosophila melanogaster led to the identification of the bazo oka, crumbs and discs large group of genes implicated in the generation of cell polarity. In addition, the components of the discs large group, the tumour suppressor proteins Dlg/Lgl/Scrib are involved in the regulation of cell proliferation. However, the f unction of these genes in mammals is poorly understood.The proposed project aims to understand how the proteins of the crumbs and discs large group regulate cell adhesion in mammalian epithelial cells and how they contribute to cell polarity. Moreover, the studies are anticipated to identify the important linkage between the regulation of cell polarity and cell proliferation. The main approaches and methods for the research project is a wound healing migration assay and siRNA experiments. By using these as says, we will look at the biochemistry and cell biology of the de novo assembly of epithelial cell junctions. In particular, we will focus on the identification of the network of protein interactions between components of the bazooka, crumbs and discs large group and how these protein complexes contribute to cell junction formation and cell polarity. Furthermore, the role of Rho-family GTPases such as Rho, Rad and Cdc42 in the formation of cell adhesion will be assessed.Finally, the proteins Dig, Lgl and S crib are considered to have a potential function in the control of cell proliferation. We will dissect the molecular events by which these proteins link cell polarity and cell proliferation by using a combination of siRNA, microinjection and live-cell imaging techniques. The results of the proposed project will have important implications for the field of epithelial cell biology and embryonic development.
Original text from CORDIS.
Participants
- UNIVERSITY COLLEGE LONDON · LONDONCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union