Role of phosphoinositides during collective directed migration

Supervising PI

Sandrine Etienne-Manneville (website)

ESR6 Shailaja Seetharaman

Project Description

The goal of this project is to determine the role of phosphoinositides and regulatory enzymes (PI3K and PTEN) in the front-to-rear polarization during collective migration of normal and tumorous cells.

The localization of PIPs and the distribution of PTEN and PI3K will be investigated in vitro and in vivo. In vitro collective migration will be analysed using glial cells migrating in a wound-healing assay. This assay has been thoroughly characterized and successfully used in the lab. The distribution of phosphoinositides will be analysed in these various conditions. Preliminary results obtained in vitro indicate that the distribution of PIP3 and PIP2 is strongly polarized, and that PIP2 synthesis by the lipid phosphatase PTEN was required for directed migration. The role of the polarized distribution of phosphoinositides in polarity signalling will then be determined. PTEN and/or PI3K activity will be inhibited using siRNA or pharmacological inhibitors. Light inducible targeting systems will be used to induce localized changes in phosphoinositide concentrations (collaboration with the Arkowitz group ). The impact of these modifications on integrin and cadherin-mediated polarity signals will be determined. The influence of phosphoinositide distribution on the polarized recycling of integrins and cadherins will be determined by video microscopy. The consequences of phosphoinositide misregulation on polarity signalling will be determined, focussing more particularly on the polarized recruitment of PAR proteins.

Phosphatidyl inositol signalling is perturbed in a vast majority of glioblastomas, tumors that derive from glial cells or their precursors, such as astrocytes. In parallel, the impact of phosphatidyl signalling on the migratory properties of primary astrocytes, neural precursors and glioblastoma cells injected in the zebrafish brain will be determined. How changes in phosphatidyl signalling promotes cell invasion and favors specific route of migration in the brain will be investigated.

This project will broaden our understanding of the role of phosphoinositides in collective directed migration and invasion. and should lead to a better understanding of the consequences of alterations of PTEN or PI3K signalling in cancer cell invasion.

Summary of Results

Cells in our body polarise and move from one part to another and help perform different functions like tissue development, repair and wound healing. Cell migration also contributes to diseases such as cancer, cardiovascular diseases etc. Cells migrate out from a primary tissue and form a secondary tumour elsewhere in the body, a process that is highly aggressive in case of glioblastomas, which are the most lethal brain tumour. Thus, understanding the molecular mechanisms controlling cell polarity and migration are crucial in order to design targeted therapies for cancer. A wide number of genes are altered in cancer cells and in particular, the function of PTEN is altered in more than 60% of glioblastomas. PTEN is a tumour suppressor protein and mutations in this gene are linked to high tumour invasiveness.

Therefore, my project aims at understanding the effects of phosphoinositide signalling (which involves PTEN) in cancer progression.

We have shown that PTEN alters the cytoskeleton and promotes collective cell migration. We observed that microtubules, one of the key cytoskeletal networks, is altered by the inhibition of phosphoinositide signalling. We then showed that by acting downstream of integrin and phosphoinositide signalling, microtubules mediate how cells sense different mechanical and biochemical cues from their microenvironment and alter migration and invasion. In the past, several therapeutic drugs have been designed to stop cells from dividing as well as cells from migrating out large distances from a primary tumour. Major chemotherapeutic drugs such as Taxol (Paclitaxel) and Vinca alkaloids (Vinblastine and Vincristine) act on the microtubule network. Thus, our research on the role of PTEN and microtubules might provide more information on how we can further control cancer invasion using these two targets as potential therapeutic strategies. 


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