Formation of Golgi-Derived Active Zone Precursor Vesicles
Vesicular trafficking of presynaptic and postsynaptic components is emerging as a general cellular mechanism for the delivery of scaffold proteins, ion channels, and receptors to nascent and mature synapses. However, the molecular mechanisms leading to the selection of cargos and their differential transport to subneuronal compartments are not well understood, in part because of the mixing of cargos at the plasma membrane and/or within endosomal compartments. In the present study, we have explored the cellular mechanisms of active zone precursor vesicle assembly at the Golgi in dissociated hippocampal neurons of Rattus norvegicus. Our studies show that Piccolo, Bassoon, and ELKS2/CAST exit the trans-Golgi network on a common vesicle that requires Piccolo and Bassoon for its proper assembly. In contrast, Munc13 and synaptic vesicle proteins use distinct sets of Golgi-derived transport vesicles, while RIM1α associates with vesicular membranes in a post-Golgi compartment. Furthermore, Piccolo and Bassoon are necessary for ELKS2/CAST to leave the Golgi in association with vesicles, and a core domain of Bassoon is sufficient to facilitate formation of these vesicles. While these findings support emerging principles regarding active zone differentiation, the cellular and molecular analyses reported here also indicate that the Piccolo-Bassoon transport vesicles leaving the Golgi may undergo further changes in protein composition before arriving at synaptic sites.
Available from: PubMed Central
- " through active transport ( Goldstein et al . , 2008 ; Hirokawa et al . , 2010 ; Figure 1A ) . It has been suggested that several AZ proteins , including bassoon , piccolo and ELKS , are trafficked as preassembled complexes , whereas SV proteins and a distinct set of AZ proteins are transported by other types of vesicles ( Shapira et al . , 2003 ; Maas et al . , 2012 ) . However , this notion has become questionable since SV proteins and AZ proteins were reported to be co - trafficked , likely via heterogeneous multi - vesicle transport complexes ( Tao - Cheng , 2007 ; Bury and Sabo , 2011 ; Wu et al . , 2013 ) . Due to the heterogeneity of these vesicles and potential co - trafficking of various ca"
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ABSTRACT: The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the structural basis for several specialized axonal structures, such as the axon initial segment (AIS) and presynaptic boutons. Emerging evidence suggest that the unique cytoskeleton organization in the axon is essential for its structure and integrity. In addition, the increasing number of neurodevelopmental and neurodegenerative diseases linked to defect in actin- and microtubule-dependent processes emphasizes the importance of a properly regulated cytoskeleton for normal axonal functioning. Here, we provide an overview of the current understanding of actin and microtubule organization within the axon and discuss models for the functional role of the cytoskeleton at specialized axonal structures.
Frontiers in Molecular Neuroscience 08/2015; 8:44. DOI:10.3389/fnmol.2015.00044 · 4.08 Impact Factor
Available from: sciencedirect.com
- "In addition, they can rapidly accumulate at new axodendritic contact sites and become capable of stimulation-evoked SV recycling (Ahmari et al., 2000; Washbourne et al., 2002; Sabo et al., 2006). On the other hand, the 80-nm-dense core Piccolo-Bassoon transport vesicles (PTVs) are proposed to represent modular packets that assemble the AZ cytomatrix in vertebrate neurons (Zhai et al., 2001; Shapira et al., 2003; Maas et al., 2012). Interestingly, recent electron micrographic (EM) and live-imaging studies reported that AZ and SV proteins may be preassembled into multivesicle transport complexes and cotrafficked in cultured neurons (Tao-Cheng, 2007; Bury and Sabo, 2011). "
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ABSTRACT: The location, size, and number of synapses critically influence the specificity and strength of neural connections. In axons, synaptic vesicle (SV) and active zone (AZ) proteins are transported by molecular motors and accumulate at discrete presynaptic loci. Little is known about the mechanisms coordinating presynaptic protein transport and deposition to achieve proper distribution of synaptic material. Here we show that SV and AZ proteins exhibit extensive cotransport and undergo frequent pauses. At the axonal and synaptic pause sites, the balance between the capture and dissociation of mobile transport packets determines the extent of presynaptic assembly. The small G protein ARL-8 inhibits assembly by promoting dissociation, while a JNK kinase pathway and AZ assembly proteins inhibit dissociation. Furthermore, ARL-8 directly binds to the UNC-104/KIF1A motor to limit the capture efficiency. Together, molecular regulation of the dichotomy between axonal trafficking and local assembly controls vital aspects of synapse formation and maintenance.
Neuron 05/2013; 78(6). DOI:10.1016/j.neuron.2013.04.035 · 15.05 Impact Factor
Available from: Markus Schröder
- "Bassoon and its paralogue Piccolo are transported into the axon on membranous organelles , , , . To check whether the defect in supply of mobile GFP-BsnS2845A contributes to observed decreased recovery we analyzed the mobility properties of fluorescently-labeled vesicles in neurons transfected with wt and mutant constructs. "
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ABSTRACT: The proper organization of the presynaptic cytomatrix at the active zone is essential for reliable neurotransmitter release from neurons. Despite of the virtual stability of this tightly interconnected proteinaceous network it becomes increasingly clear that regulated dynamic changes of its composition play an important role in the processes of synaptic plasticity. Bassoon, a core component of the presynaptic cytomatrix, is a key player in structural organization and functional regulation of presynaptic release sites. It is one of the most highly phosphorylated synaptic proteins. Nevertheless, to date our knowledge about functions mediated by any one of the identified phosphorylation sites of Bassoon is sparse. In this study, we have identified an interaction of Bassoon with the small adaptor protein 14-3-3, which depends on phosphorylation of the 14-3-3 binding motif of Bassoon. In vitro phosphorylation assays indicate that phosphorylation of the critical Ser-2845 residue of Bassoon can be mediated by a member of the 90-kDa ribosomal S6 protein kinase family. Elimination of Ser-2845 from the 14-3-3 binding motif results in a significant decrease of Bassoon's molecular exchange rates at synapses of living rat neurons. We propose that the phosphorylation-induced 14-3-3 binding to Bassoon modulates its anchoring to the presynaptic cytomatrix. This regulation mechanism might participate in molecular and structural presynaptic remodeling during synaptic plasticity.
PLoS ONE 03/2013; 8(3):e58814. DOI:10.1371/journal.pone.0058814 · 3.23 Impact Factor
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