Projects / Programmes
Nanophysiology of exocytosis in health and disease
| Code |
Science |
Field |
Subfield |
| 3.03.00 |
Medical sciences |
Neurobiology |
|
| Code |
Science |
Field |
| B000 |
Biomedical sciences |
|
| Code |
Science |
Field |
| 3.01 |
Medical and Health Sciences |
Basic medicine |
astrocytes, exocytosis, neurotrophic factor (BDNF), cholesterol, ketamine, depression, intellectual dissability, superresolution microscopy
Researchers (14)
Organisations (2)
Abstract
In multicellular organisms cell to cell communication is a necessity. The most efficient and unifying mode of communication between eukaryotic cells is represented by regulated exocytosis. In this process, signalling molecules are first densely packed in membrane bound vesicles that are then transported to the plasma membrane. Upon stimulation vesicles containing signalling molecules fuse with the plasma membrane and release their content into the extracellular space. In the initial stage of the fusion process, the release of signalling molecules is hindered by a narrow, channel-like structure, the fusion pore. The control of the formation and the expansion of the fusion pore has been traditionally attributed to proteins, such as the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and SM (Sec1/Munc18) proteins. However, it is now clear that also components that were long considered to be merely building blocks of biological membranes, like lipids and their metabolites, can affect exocytosis in either direct (through changes in membrane biophysical properties) or indirect (e.g. by affecting the local calcium concentration) manner. Cholesterol is an essential component of animal cell membranes, representing approximately a quarter of all lipids in the plasma membrane. It is still contested if cellular cholesterol affects the release of signalling molecules from different cell types and what is the mechanism of its action. Specifically, we lack insight into the initial stages of the vesicular fusion, where cholesterol may affect the formation of fusion pores, either directly or indirectly. It has been shown that high levels of ketamine that is used for anaesthesia decrease serum cholesterol levels. However, it remains to be studied if low levels of ketamine, which have proved an extremely effective treatment for depression, bipolar disorder and suicidal behaviour, similarly decrease serum cholesterol and if this effect translates to cellular cholesterol levels. Ketamine has been shown to increase plasma levels of brain-derived neurotrophic factor (BDNF), whereas there are reports of low levels of BDNF in depressed patients. Recent reports suggest that, apart in neurons, BDNF can be synthesized also in glial cells, particularly astrocytes. Synthesized BDNF, as well as BDNF cleared from the extracellular space through rapid uptake by astrocytes, may be released by regulated exocytosis from astrocytes. In this proposal we plan to study if the long-term ketamine treatment affects the probability of BDNF secretion by regulated exocytosis from astrocytes. Moreover, we will address the question how changes in cholesterol levels affect BDNF secretion, especially the contribution of cholesterol in the initial phases of vesicular fusion. We strongly believe that the results of the proposed research are not only novel, but will provide important new insights into the fundamental physiological/biophysical aspects of exocytosis which bear important translational potential for treating different pathological conditions.
Significance for science
The proposed project aims to understand one of the most important mechanisms by which cells communicate with each other; regulated exocytosis. The relevance of this field of neurobiology is, among others, empahsized by two Nobel prizes that have been awarded in the last five decades (in 1970 to B. Katz, U. Euler, J. Axelrod, and in 2013 to J.E. Rothman, R.W. Schekman, T. Sudhof). Moreover, the impairment of exocytosis can lead to the development of several pathological conditions. Nonetheless, several key questions remain unanswered. One of these questions is conected to the role of lipids, such as cholesterol, in one of the last steps of exocytosis, i.e. in the fusion of vesicles with the plasma membrane. In part the knowledge of this process is still fragmental due to experimental inaccessibility. Therefore, we will use methods, which we introduced and developed in our laboratory to monitor physiological parameters at single cell, single organelle, and at single molecule level. These methods include STED microscopy (we have developed a two color STED system in colaboration with the research group of prof. dr. Stefan W. Hell) and electrophysiological monitoring of the membrane capacitance (we have developed our own lock-in patch-clamp amplifier, low-pass filter unit and software for acquisition and analysis).
In summary, the proposed project will:
a) generate new insights into the field of neuroscience,
b) useful for discovering new therapeutic processes and targets,
c) help to advance some of the already cutting edge technologies.
Significance for the country
The aim of the proposed project is to reveal new mechanisms in the process of regulated exocytosis, which may result in a number of pathological states. Specifically, the first mechanism is related to the conditions accompanying the use of cholesterol-lowering drugs, such as statins in dyslipidemia. According to the World health organization, approximately 39% of the world population suffered from raised cholesterol levels in 2008 (http://www.who.int/gho/ncd/risk_factors/cholesterol_text/en/). In addition to the high mortality due to the cardiovaskular diseases ralated to the raised cholesterol levels, there are also profound neurological side-effects, such as a higher risk of developing Alzheimer disease. In addition we will consider the mechanism of action of an aneasthetic ketamine, which can in lower doses be used for treating psychiatric diseases, such as depression.
Therefore, the results of our work will not be limited to the fundamental research of (patho)physiological cell mechanisms only; the impact will be wider, since the results of our work will lead to the identification of new potential targets for novel drug development for different neurological disorders.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
