NEURONAL POROSOME IN THE RAT AND CAT BRAIN
V.G. Okuneva, N.J. Japaridze, N.T. Kotaria, M.G. Zhvania 1
Life Science Research Center, Tbilisi, Georgia;
1 e-mail: mzia_zhvania@iliauni.edu.ge
It is well established that during cell secretion, membrane-bound secretory vesicles dock and fuse at the base
of supramolecular cup-shaped structures at the cell plasma membrane called «porosomes», to expel intra-vesicular
contents to the outside. In neurons, it has been demonstrated that 12—17 nm cuđ-shaped lipoprotein
structure possessing a central plug are present at the presynaptic membrane, where 50 nm in diameter synaptic
vesicles transiently dock and fuse to release neurotransmitter. In the past decade, the neuronal porosome has
been isolated and its major chemical composition determined. Additionally, the porosome has been both structurally
and functionally reconstituted into artificial lipid membrane, establishing its role as the secretory portal in
neurons. Studies utilizing atomic force and electron microscopy, combined with electron density and 3D contour
mapping, provide at the nanoscale, the structure and assembly of proteins within the neuronal porosome. In the
current study, ultrahigh resolution imaging of the presynaptic membrane of isolated brains from both rats and
cats, demonstrate for the first time, the presence of neuronal porosomes in cat brain, and further confirms the
presence of porosomes at the presynaptic membrane in rat brain synaptosomes. Results from the present study
further confirm the cup-shaped morphology of porosomes in the rat brain, and demonstrates their similar shape
and size in the cat nerve terminal. The study also demonstrates for the first time, the universal presence of similar
porosomes in different species of mammals.
Key words: neuronal porosome, electron microscopy, cat, rat
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