Article

The role of snapin in neurosecretion: Snapin knock-out mice exhibit impaired calcium-dependent exocytosis of large dense-core vesicles in chromaffin cells

Synaptic Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3701, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 12/2005; 25(45):10546-55. DOI: 10.1523/JNEUROSCI.3275-05.2005
Source: PubMed

ABSTRACT

Identification of the molecules that regulate the priming of synaptic vesicles for fusion and the structural coupling of the calcium sensor with the soluble N-ethyl maleimide sensitive factor adaptor protein receptor (SNARE)-based fusion machinery is critical for understanding the mechanisms underlying calcium-dependent neurosecretion. Snapin binds to synaptosomal-associated protein 25 kDa (SNAP-25) and enhances the association of the SNARE complex with synaptotagmin. In the present study, we abolished snapin expression in mice and functionally evaluated the role of Snapin in neuroexocytosis. We found that the association of synaptotagmin-1 with SNAP-25 in brain homogenates of snapin mutant mice is impaired. Consequently, the absence of Snapin in embryonic chromaffin cells leads to a significant reduction of calcium-dependent exocytosis resulting from a decreased number of vesicles in releasable pools. Overexpression of Snapin fully rescued this inhibitory effect in the mutant cells. Furthermore, Snapin is relatively enriched in the purified large dense-core vesicles of chromaffin cells and associated with synaptotagmin-1. Thus, our biochemical and electrophysiological studies using snapin knock-out mice demonstrate that Snapin plays a critical role in modulating neurosecretion by stabilizing the release-ready vesicles.

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Available from: Zu-Hang Sheng, Jun 25, 2014
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    • "Finally, considering the multivalent role of Snapin in intracellular trafficking, there is also another possibility to discuss the physiologic relevance of the interaction between IncB and Snapin. Snapin was first identified as a neuronal SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-binding protein (Ilardi et al., 1999), which is critical in facilitating synchronized fusion of synaptic vesicles in neurons (Tian et al., 2005). These SNARE proteins present on opposing membranes drive membrane fusion by bringing vesicle and target membranes close together through the assembly of an SNARE-containing four-helix bundle (Jahn and Scheller, 2006). "
    [Show abstract] [Hide abstract] ABSTRACT: Chlamydia (C.) psittaci, the causative agent of psittacosis in birds and humans, is the most important zoonotic pathogen of the family Chlamydiaceae. During a unique developmental cycle of this obligate intracellular pathogen, the infectious elementary body gains access to the susceptible host cell, where it transforms into the replicative reticulate body. C. psittaci uses dynein motor proteins for optimal early development. Chlamydial proteins that mediate this process are unknown. Two-hybrid screening with the C. psittaci inclusion protein IncB as bait against a HeLa Yeast Two-hybrid (YTH) library revealed that the host protein Snapin interacts with IncB. Snapin is a cytoplasmic protein that plays a multivalent role in intracellular trafficking. Confocal fluorescence microscopy using an IncB-specific antibody demonstrated that IncB, Snapin, and dynein were co-localized near the inclusion of C. psittaci-infected HEp-2 cells. This co-localization was lost when Snapin was depleted by RNAi. The interaction of Snapin with both IncB and dynein has been shown in vitro and in vivo. We propose that Snapin connects chlamydial inclusions with the microtubule network by interacting with both IncB and dynein.
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    • "Finally, considering the multivalent role of Snapin in intracellular trafficking, there is also another possibility to discuss the physiologic relevance of the interaction between IncB and Snapin. Snapin was first identified as a neuronal SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-binding protein (Ilardi et al., 1999), which is critical in facilitating synchronized fusion of synaptic vesicles in neurons (Tian et al., 2005). These SNARE proteins present on opposing membranes drive membrane fusion by bringing vesicle and target membranes close together through the assembly of an SNARE-containing four-helix bundle (Jahn and Scheller, 2006). "
    [Show abstract] [Hide abstract] ABSTRACT: Chlamydia (C.) psittaci, the causative agent of psittacosis in birds and humans, is the most important zoonotic pathogen of the family Chlamydiaceae. During a unique developmental cycle of this obligate intracellular pathogen, the infectious elementary body gains access to the susceptible host cell, where it transforms into the replicative reticulate body. C. psittaci uses dynein motor proteins for optimal early development. Chlamydial proteins that mediate this process are unknown. Two-hybrid screening with the C. psittaci inclusion protein IncB as bait against a HeLa Yeast Two-hybrid (YTH) library revealed that the host protein Snapin interacts with IncB. Snapin is a cytoplasmic protein that plays a multivalent role in intracellular trafficking. Confocal fluorescence microscopy using an IncB-specific antibody demonstrated that IncB, Snapin, and dynein were co-localized near the inclusion of C. psittaci-infected HEp-2 cells. This co-localization was lost when Snapin was depleted by RNAi. The interaction of Snapin with both IncB and dynein has been shown in vitro and in vivo. We propose that Snapin connects chlamydial inclusions with the microtubule network by interacting with both IncB and dynein.
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