Projects / Programmes
Molecular properties of the fusion pore
| Code |
Science |
Field |
Subfield |
| 3.03.00 |
Medical sciences |
Neurobiology |
|
| Code |
Science |
Field |
| B640 |
Biomedical sciences |
Neurology, neuropsychology, neurophysiology |
| Code |
Science |
Field |
| 3.05 |
Medical and Health Sciences |
Other medical sciences |
fusion pore, exocytosis, electrophysiology, biophysics, molecular biology, neurophysiology
Researchers (10)
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
1683 |
Celica BIOMEDICAL |
Ljubljana |
1506854 |
1,782 |
Abstract
A key problem to be solved in neurobiology is to understand the mechanism of signal transduction in a chemical synapse and the release of hormones from neuroendocrine cells. In both cases, the critical process involves vesicles in which the chemical messengers and hormones are stored. The release of vesicle cargo to the extracellular medium is mediated by exocytosis, the merger of vesicular and plasma membranes, which leads to the formation of a fusion pore, an aqueous channel providing a conduit through which secretory products exit cells. Studies point to a two-stage mechanism of fusion pore formation – an initially metastable narrow fusion pore is followed by a sudden enlargement. However, the molecular mechanisms governing this process are unclear. Specifically, we lack insight into the nature of the supramolecular structure of the fusion pore and how specific proteins and other fusion pore associated molecules modulate the rapid transition of the fusion pore from a relatively impermeable to a fully permeable state. To understand the fusion pore mechanisms we plan to study the role of several proteins at the level of a single fusion pore in pituitary lactotrophs by electrophysiological, optical and molecular biology approaches. The advantage of using lactotrophs as a model system over neurones is that the transient fusion pores in lactotrophs exhibit a remarkable robust stability, whereas in neurons this intermediate fusion state is too short to be reliable detected experimentally. SNARE proteins are thought to mediate membrane fusion by forming stable complexes which are initiated at their N-terminal ends and then progress towards the C-terminal membrane anchors (zippering), thereby releasing energy. This process appears to be modulated by SNARE-associated proteins such as Sec1/Munc 18 (SM proteins) via their interaction with specific SNARE partners, such as syntaxin1. Previous amperometric studies indicated that SM proteins may affect the stability of the fusion pore. However, the critical question is to directly monitor the fusion pore properties, which can only be done by high-resolution membrane capacitance techniques, to test whether the interactions between the SM proteins and SNARE complex proteins affects the physiological properties of the transient fusion pore, the intermediate state leading to full fusion. In this proposal we plan to study how mutations of the SM proteins, affecting the SNARE protein syntaxin1 at different stages of SNARE zippering, modulate the single fusion pore properties. We strongly believe that these experiments will provide new direct evidence to understand whether transient fusion pore properties are subject to physiological regulation in terms of kinetics and fusion pore diameter by the SM proteins.
Significance for science
Hormones and neurotransmitters are chemical messengers that relay vital instructions through out our entire body. The release of these signalling molecules is regulated by proteins. However, we lack insight into the nature of the interactions between specific proteins, which would enable a better understanding of how specific proteins and other fusion pore associated molecules modulate the release. The results of this study importantly contribute to a better understanding of the fusion pore regulation. Specifically, we provide evidence if/how SNARE-associated protein Munc18-1 affects the kinetics and conductance of the fusion pore. The findings therefore provide new direct evidence toward a better understanding of the single cell release of signaling molecules, which is needed to better understand the mechanism of signal transduction of chemical synapse and of the release of hormones.
Significance for the country
1.) National development is tightly related to the industrial progress, which in turn depends on the findings of basic science. As one of the topical fields of research our research contributes to the basic knowledge of neuroscience. This is especially relevant for Slovenia, where pharmaceutical industry is well established. Translation of the basic research to industry is though a relatively slow process. 2.) Highly important theme of our research is mirrored also in several scientific publications with high impact factor and in the organization of international meetings. This has helped to gain visibility of individuals, and the scientific community in Slovenia as well. 3.) Education of personnel benefited by supporting our proposal. To contribute to the global effort, it is imperative to train young researchers to gain competitiveness in fundamental research. Research project has also facilitated the international collaborations.
Most important scientific results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si
