Phospholipid transfer protein (PLTP) is involved in transfer of fats in the blood to and from the cells. To perform these well-known functions, PLTP is required to be present only on the outside of the cell, in the so-called extracellular space. Surprisingly, recent studies have shown that PLTP is also present in the nucleus, which is a part of the cell that regulates expression of cell proteins and how the cell functions. However, at this time, nothing is known about how PLTP functions inside the nucleus. This application proposes to establish a new paradigm that PLTP transfers fats from the outside of the cell into the nucleus, and by doing so regulates intranuclear functions that are important for normal cell functioning. Furthermore, recent studies have shown that PLTP itself, unrelated to its fat transfer functions, is involved in regulation of processes in the cell. Therefore, the application proposes to test how and by which mechanism PLTP affects intranuclear processes that regulate expression of proteins, and how parts of PLTP?s genetic code modulate fate of the cell. To achieve these goals, the PLTP molecule will be changed, creating PLTP mutants that lack specific properties, such as ability to transfer fats, enter the nucleus or bind to its intranuclear targets. These studies will test the functions related to transfer of fats to the nucleus and binding to DNA (genetic code in the nucleus).
The proposed studies address significant basic research questions that have not been previously evaluated, but are critical to better understanding of both normal and abnormal cellular functioning. The new ideas that will be tested in this project have great potential to change thinking about regulation of cellular function, which would have an impact on nearly all aspects of cell biology. Furthermore, normal PLTP levels and activity appear to be of great importance, but relative lack of knowledge of its functions at the cellular level currently prevents further development of models and methods that would harness its functional properties to prevent or treat chronic human disorders and diseases, including cancer, diabetes and Alzheimer?s disease. Without clear understanding of PLTP?s normal functions, particularly those related to the nucleus, it would be impossible to understand how defects in PLTP functions cause disease. Therefore, the proposed studies will form an important foundation for advancement of science in general, and for improvement and development of new approaches to prevention and treatment of human diseases.
In this project, we confirmed our main idea that fats found outside of the cells can be transported by phospholipid transfer protein (PLTP) directly into the nucleus of the cell. This process leads to changes in proteins that regulate DNA function (chromatins), which modify expression of genes and thus also function of the cells. We also discovered that fats from diet affect function of chromatins in rat brain. Furthermore, fats present in the blood of people who suffer from severe infections (sepsis) have a marked effect on chromatins of human cells lining blood vessels, which may be relevant for changes in organ function in sepsis. These discoveries may explain how fats, including those absorbed from food, affect cellular fate, and consequently development of many human diseases, including diseases of the brain. Furthermore, in collaboration with other sientists we discovered that PLTP has a boomerang shape, confirming computer simulations based on structure of similar proteins. We also discovered how PLTP interacts with particles that carry fat in the blood (lipoprotein particles). These findings are important because they answer questions related to PLTP’s structure and the mechanisms of PLTP-lipoprotein interactions, relevant for development of medications that could modify levels of fat particles, or the so-called good cholesterol (HDL), in human blood, and could lead to new therapies for heart disease and stroke. We also discovered presence of a new molecule involved in metabolism of fats in human brain, apolipoprotein (a), thus opening a new area of research. This is the first report of the apo(a) presence in the brain in humans. We also reported localization of another protein involved in fat metabolism in the brain, lipoprotein lipase (LPL), an important enzyme that has not been previously described in human brain. Furthermore, we found that LPL is greatly reduced in Alzheimer’s disease, particularly in a part of the brain that is important for creation of new brain cells (neurons), a process that is considered exceptionally important for repair of the brain tissue. The project provided resources for training and one-on-one mentoring of undergraduate students and post-doctoral fellows, thus contributing to the educational aspects of the project. It also allowed establishing of important collaborations among researchers from different institutions and areas of science, and promoted education of general public through free public lectures on issues of science, healthy living, disease prevention and other relevant issues.
