Calcium-induced exocytosis from actomyosin-driven, motile varicosities formed by dynamic clusters of organelles |
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Authors: | Guy Malkinson Zohar M Fridman Dotan Kamber Ada Dormann Eli Shapira Micha E Spira |
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Institution: | (1) Department of Neurobiology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel |
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Abstract: | Varicosities are ubiquitous neuronal structures that appear as local swellings along neurites of invertebrate and vertebrate
neurons. Surprisingly little is known about their cell biology. We use here cultured Aplysia neurons and demonstrate that varicosities are motile compartments that contain large clusters of organelles. The content
of varicosities propagate along neurites within the plasma membrane “sleeve”, split and merge, or wobble in place. Confocal
imaging, retrospective immunolabeling, electron microscopy and pharmacological perturbations reveal that the motility of the
varicosities’ organelle content occurs in concert with an actin scaffold and is generated by actomyosin motors. Despite the
motility of these organelle clusters within the cytoplasm along the neurites, elevation of the free intracellular calcium
concentration within varicosities by trains of action potentials induces exocytosis followed by membrane retrieval. Our observations
demonstrate that varicosities formed in the absence of postsynaptic cells behave as “ready to go” prefabricated presynaptic
terminals. We suggest that the varicosities’ motility serves to increase the probability of encountering a postsynaptic cell
and to rapidly form a functional synapse.
Electronic Supplementary Material Supplementary material is available in the online version of this article at
These authors contributed equally to the paper. |
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