Rala and Ralb Function As the Critical Gtp Sensors for Gtp-dependent Exocytosis.
From: Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada M5T 2S8.
The Journal of neuroscience : the official journal of the Society for Neuroscience
- Publish Date: Jan 2007
- ISSN: 1529-2401
- Volume: 27
- Issue: 1
- Pages: 190-202
- Medium: Internet
- Language: English
- Citation (JAMA): Li Gang, Han Liping, Chou Ting-Chieh, et al. Rala and Ralb Function As the Critical Gtp Sensors for Gtp-dependent Exocytosis.. J. Neurosci. Jan 2007;27:190-202
Abstract
Although it has been established that the activation of GTPases by non-hydrolyzable GTP stimulates neurotransmitter release from many different secretory cell types, the underlying mechanisms remain unclear. In the present study we aimed to elucidate the functional role(s) for endogenous Ras-like protein A (RalA) and RalB GTPases in GTP-dependent exocytosis. For this purpose stable neuroendocrine pheochromocytoma 12 (PC12) cell lines were generated in which the expressions of both RalA and RalB were strongly downregulated. In these double knock-down cells GTP-dependent exocytosis was reduced severely and was restored after the expression of RalA or RalB was reintroduced by transfection. In contrast, Ca2+-dependent exocytosis and the docking of dense core vesicles analyzed by electron microscopy remained unchanged in the double knock-down cells. Furthermore, the transfected RalA and RalB appeared to be localized primarily on the dense core vesicles in undifferentiated and nerve growth factor-differentiated PC12 cells. Our results indicate that endogenous RalA and RalB function specifically as GTP sensors for the GTP-dependent exocytosis of dense core vesicles, but they are not required for the general secretory pathways, including tethering of vesicles to the plasma membrane and Ca2+-dependent exocytosis.
Mesh Headings (Keywords): Animals, Calcium, Exocytosis, Guanosine Triphosphate, PC12 Cells, Rats, ral GTP-Binding Proteins
Check for Full Text / PubMed Unique Identifier (PMID): 17202486
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