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Final Report Summary - IRTIM (Investigating the role of transporters in invasive migration through junctions)

Background: A major challenge in biology is to understand how cancer and immune cells traverse through tissue barriers. Immune cells carry out such invasive migration during several steps in their life cycle, most notably when they cross the endothelial blood vessel wall to chase infections in tissues. Metastatic cancer cells move into and out of the blood using similar strategies to enable their spread. These invasive processes require coordination of the movement, adhesion and cellular properties of the invading cell with changes in the junctional adhesion and cellular properties of the penetrated tissue. Yet precisely how this coordination occurs within an organism’s microenvironment remains poorly understood. Identification of new proteins and processes needed for invasion, and an ability to visualize the dynamics of cellular behavior in vivo would greatly facilitate an understanding of this process and the development of therapies for both autoimmune diseases and cancer. Drosophila offers powerful, speedy genetics, and permits excellent imaging. Drosophila possess immune cells called hemocytes, the major subset of which act as macrophages, clearing apoptotic cells during development, responding to wounds and tumors, as well as destroying bacteria and viruses that can cause disease. We have shown previously that these hemocytes migrate into the region of the germband of the embryo by penetrating between two adhering epithelial barriers, and have conducted screens to identify new proteins that are required for this invasive migration. Six such proteins that affected movement into the tail were categorized based on their structure as transporters. These are prime candidates to serve in interesting signaling processes involved in tissue penetration. We sought to understand their role better and leverage our findings for greater insights into vertebrate immune cell barrier penetration.
Summary of project objectives: The objectives of this project are: 1. To Identify the cell surface transporters required in hemocytes for invasive migration; 2. To identify the invasive process the chosen cell surface transporter is involved in Drosophila; 3. To determine if the chosen transporter is required for transmigration of vertebrate immune cells.
Main results: We have focused on one novel transporter we identified, which is conserved in vertebrates and required for the invasive migration of macrophages during Drosophila development. We have found that it can be localized to the cell surface in macrophage extensions, but is mainly found in the Golgi. We have characterized a transposon allele that acts as a null as the excision allele seemed to have developmental defects. We have shown that this transporter is required for the presence of T antigen glycosylation on the surface of macrophages. We have also shown that this modification is found on the macrophages that carry out invasive migration but not those that migrate along a non invasive route. This is exciting, as surface localization of T antigen in vertebrates is found mainly on cancer cells, and appears to be required for metastasis. We have shown that the transporter is also required for the down regulation of N-Cadherin, an adhesion molecule. We speculate that this down regulation is part of a maturation program designed to prepare the macrophages for the subsequent developmental step of invasion. We have made mutants of this transporter in mammalian dendritic cells, and have shown that this leads to a migratory defect in 3D extracellular matrix environment (ECM), along with a maturation defect.
Broader impact: While this project is motivated by a desire to conduct research into the fundamental mechanisms of cellular biology, it is also aimed at identifying a new protein involved in the invasive migration of vertebrates and thus has additional potential implications for the treatment of autoimmune diseases and metastatic cancer. We have demonstrated that the vertebrate ortholog of the Drosophila transporter is required in immune cells for migration through ECM and immune cell maturation. We are currently investigating the importance of this transporter for cancer metastasis and immune responses and believe the prospects are bright for identifying relevance that would lead to pursuit of therapeutic objectives.
Integration and future perspective: The fellow was able to 1) build a vibrant, international and interdisciplinary research group (9.5 group members: 1 lab manager, 4 graduate students, 2 post docs, 2 technicians, one half time modeler) 2) attract over 1 million Euros in competitive research funding to the group and 3) disseminate her work through talks at leading conferences in the US and Europe as well as through visits to renowned international research institutions on both continents. The fellow has integrated extremely well at the institute, having helped organize events to create community among the biology faculty, and being sought as a committee member by graduate students from many different groups. Every year the fellow has taught a set of graduate students diverse both in their country of origin and in their prior training. She has participated actively in transmitting her findings and her love of science to the general public. She will continue to forge ahead on all these fronts as an independent scientist and looks forward to contributing to basic research that leads to insights relevant to the public’s health throughout her future career.

Reported by

Institute of Science and Technology Austria


Life Sciences
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