Role of TPD52-like proteins in cell migration and disease

Cells have lots of proteins on their surface. They use these proteins to sense the environment and also to stick themselves to surfaces and move around. One way a cell can change how it senses or how it moves is to alter how many of these proteins are on the cell surface. A cell does this by taking these proteins into the cell and then putting them back onto the surface. Speeding up or slowing down the uptake or return legs of the pathway can tweak this "recycling" process. These tweaks work because they change the number of proteins on the surface and thereby alter how the cell senses or moves. Scientists know a lot about the uptake leg (endocytosis) but they know much less about the return leg. My lab has found that two proteins (TPD52 and TPD54) might be involved in the return leg. They are found together with three other proteins (Rab4, Rab11a and Rab25), which are known to be involved with the return leg, and changing how cells move. We are proposing to pin down exactly how TPD52 and TPD54 are involved in the uptake and return legs of the recycling pathway. Next, we want to find out which other Rabs the TPD proteins move around with and which ones they stick to (humans have ~70 Rabs!) and if sticking changes the activity of Rabs. We'll look at how these proteins affect cell movement. Finally, we will look at the sticky proteins on the surface of cells called integrins, and see if TPD proteins are needed for recycling integrins. Finding out all of these things is important because recycling is at the heart of many different things that cells do, not just sensing the environment and moving, but also how cells respond to drugs, how they control cell division, and much more. Also, we're interested in cell movement because cells need to move while an animal is developing and when it responds to injury. Finally, in diseases such as cancer, cell movement makes the disease very difficult to treat due to cancer cells moving away and starting new tumours somewhere else. This is known as "the cancer spreading in the body". In fact, TPD52 and TPD54 were first identified in breast cancer patients with fast growing and moving tumour cells. Understanding what TPD proteins do in cells to recycle proteins like integrins is important to understanding cell movements in disease and may provide new targets for future therapies.

Cells modulate the levels of proteins on their surface. They do this to control how they respond to external cues and to change how they adhere to, and migrate on, surfaces. One way that cells modulate the density of their cell surface proteins is to change the relative rates of internalization and reinsertion of proteins at the plasma membrane. While much is known about the endocytic machinery, less is known about the proteins involved in recycling receptors back to the plasma membrane. The tumour protein D52 (TPD52)-like proteins TPD52 and TPD54 are known to be involved in intracellular membrane trafficking, but their precise role is unclear. They are found on various types of intracellular vesicles and our preliminary work shows that these vesicles are positive for Rab4, Rab11a and Rab25 (recycling vesicles) but not other Rabs such as Rab5, Rab7 and Rab9. Cell migration and invasion is dependent on the recycling of integrins, and Rab4, Rab11a and Rab25 are known to be involved in these pathways.
There are three aims of this project. First, we will define the function of TPD52 and TPD54 on the endocytic recycling pathway. Second, we will uncover the role of TPD52 and TPD54 in cell migration and invasion. Third, we will understand the activity of TPD52 and TPD54 in integrin recycling. The project will therefore investigate membrane trafficking in the physiological process of cell migration which is important in health and in diseases such as cancer and heart disease.

This is a cell biology project which will investigate a family of proteins whose expression is altered in cancer. The central hypothesis is that these proteins are important for recycling integrins and thus controlling cell movement and invasion in metastatic conditions. Potentially the work may have broader impacts because recycling is important for numerous processes, the most well-known being cholesterol homeostasis. Recycling is also responsible for drug tolerance which is a major problem for patients, e.g. in pain management.
The main beneficiaries of the results will be the academic community followed by scientists in the commercial private sector: pharmaceutical companies, small biotech companies and contract research organisations. The academic community will also benefit from the tools, techniques and code that we generate. All of which will be made available upon publication (see Pathways to Impact for more detail).
We have a defined dissemination plan in place which encompasses social media, prepublication via preprint servers, blogging and publicising the publications that result from the project widely. This ensures that our work is seen by scientists outside the realm of cell biology, and even interested members of the public.
The PI will manage the project in collaboration with the PDRA. The roles and responsibilities for day-to-day project management are described in the Justification of Resource section. Together we will decide on how to maximise the impact of the discoveries that arise from this project. The project involves collaboration with Pat Caswell's lab in Manchester. This is an excellent opportunity for our labs to network and build stronger ties for possible future work.