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Cell Apr 2024In addition to long-distance molecular motor-mediated transport, cellular vesicles also need to be moved at short distances with defined directions to meet functional...
In addition to long-distance molecular motor-mediated transport, cellular vesicles also need to be moved at short distances with defined directions to meet functional needs in subcellular compartments but with unknown mechanisms. Such short-distance vesicle transport does not involve molecular motors. Here, we demonstrate, using synaptic vesicle (SV) transport as a paradigm, that phase separation of synaptic proteins with vesicles can facilitate regulated, directional vesicle transport between different presynaptic bouton sub-compartments. Specifically, a large coiled-coil scaffold protein Piccolo, in response to Ca and via its C2A domain-mediated Ca sensing, can extract SVs from the synapsin-clustered reserve pool condensate and deposit the extracted SVs onto the surface of the active zone protein condensate. We further show that the Trk-fused gene, TFG, also participates in COPII vesicle trafficking from ER to the ER-Golgi intermediate compartment via phase separation. Thus, phase separation may play a general role in short-distance, directional vesicle transport in cells.
Topics: Animals; Synaptic Vesicles; COP-Coated Vesicles; Endoplasmic Reticulum; Calcium; Golgi Apparatus; Rats; Biological Transport; Presynaptic Terminals; Synapsins; Biomolecular Condensates; Cytoskeletal Proteins; Phase Separation
PubMed: 38552623
DOI: 10.1016/j.cell.2024.03.003 -
Cold Spring Harbor Perspectives in... Sep 2012Neurons can sustain high rates of synaptic transmission without exhausting their supply of synaptic vesicles. This property relies on a highly efficient local endocytic... (Review)
Review
Neurons can sustain high rates of synaptic transmission without exhausting their supply of synaptic vesicles. This property relies on a highly efficient local endocytic recycling of synaptic vesicle membranes, which can be reused for hundreds, possibly thousands, of exo-endocytic cycles. Morphological, physiological, molecular, and genetic studies over the last four decades have provided insight into the membrane traffic reactions that govern this recycling and its regulation. These studies have shown that synaptic vesicle endocytosis capitalizes on fundamental and general endocytic mechanisms but also involves neuron-specific adaptations of such mechanisms. Thus, investigations of these processes have advanced not only the field of synaptic transmission but also, more generally, the field of endocytosis. This article summarizes current information on synaptic vesicle endocytosis with an emphasis on the underlying molecular mechanisms and with a special focus on clathrin-mediated endocytosis, the predominant pathway of synaptic vesicle protein internalization.
Topics: Actin Cytoskeleton; Clathrin; Clathrin-Coated Vesicles; Endocytosis; Exocytosis; Intracellular Membranes; Membrane Fusion; Models, Biological; Phosphatidylinositols; Protein Transport; Synaptic Transmission; Synaptic Vesicles
PubMed: 22763746
DOI: 10.1101/cshperspect.a005645 -
Current Opinion in Neurobiology Oct 2022Sustained neurotransmission is driven by a continuous supply of synaptic vesicles to the release sites and modulated by synaptic vesicle dynamics. However, synaptic... (Review)
Review
Sustained neurotransmission is driven by a continuous supply of synaptic vesicles to the release sites and modulated by synaptic vesicle dynamics. However, synaptic vesicle dynamics in synapses remain elusive because of technical limitations. Recent advances in fluorescence imaging techniques have enabled the tracking of single synaptic vesicles in small central synapses in living neurons. Single vesicle tracking has uncovered a wealth of new information about synaptic vesicle dynamics both within and outside presynaptic terminals, showing that single vesicle tracking is an effective tool for studying synaptic vesicle dynamics. Particularly, single vesicle tracking with high spatiotemporal resolution has revealed the dependence of synaptic vesicle dynamics on the location, stages of recycling, and neuronal activity. This review summarizes the recent findings from single synaptic vesicle tracking in small central synapses and their implications in synaptic transmission and pathogenic mechanisms of neurodegenerative diseases.
Topics: Neurons; Presynaptic Terminals; Synapses; Synaptic Transmission; Synaptic Vesicles
PubMed: 35803103
DOI: 10.1016/j.conb.2022.102596 -
International Journal of Molecular... Sep 2022Bone mineralization entails two mineralization phases: primary and secondary mineralization. Primary mineralization is achieved when matrix vesicles are secreted by... (Review)
Review
Bone mineralization entails two mineralization phases: primary and secondary mineralization. Primary mineralization is achieved when matrix vesicles are secreted by osteoblasts, and thereafter, bone mineral density gradually increases during secondary mineralization. Nearby extracellular phosphate ions (PO) flow into the vesicles via membrane transporters and enzymes located on the vesicles' membranes, while calcium ions (Ca), abundant in the tissue fluid, are also transported into the vesicles. The accumulation of Ca and PO in the matrix vesicles induces crystal nucleation and growth. The calcium phosphate crystals grow radially within the vesicle, penetrate the vesicle's membrane, and continue to grow outside the vesicle, ultimately forming mineralized nodules. The mineralized nodules then attach to collagen fibrils, mineralizing them from the contact sites (i.e., collagen mineralization). Afterward, the bone mineral density gradually increases during the secondary mineralization process. The mechanisms of this phenomenon remain unclear, but osteocytes may play a key role; it is assumed that osteocytes enable the transport of Ca and PO through the canaliculi of the osteocyte network, as well as regulate the mineralization of the surrounding bone matrix via the Phex/SIBLINGs axis. Thus, bone mineralization is biologically regulated by osteoblasts and osteocytes.
Topics: Bone Matrix; Calcification, Physiologic; Collagen; Extracellular Matrix; Osteoblasts; Osteocytes
PubMed: 36077336
DOI: 10.3390/ijms23179941 -
Annual Review of Cell and Developmental... 1999Synaptic vesicles, which have been a paradigm for the fusion of a vesicle with its target membrane, also serve as a model for understanding the formation of a vesicle... (Review)
Review
Synaptic vesicles, which have been a paradigm for the fusion of a vesicle with its target membrane, also serve as a model for understanding the formation of a vesicle from its donor membrane. Synaptic vesicles, which are formed and recycled at the periphery of the neuron, contain a highly restricted set of neuronal proteins. Insight into the trafficking of synaptic vesicle proteins has come from studying not only neurons but also neuroendocrine cells, which form synaptic-like microvesicles (SLMVs). Formation and recycling of synaptic vesicles/SLMVs takes place from the early endosome and the plasma membrane. The cytoplasmic machinery of synaptic vesicle/SLMV formation and recycling has been studied by a variety of experimental approaches, in particular using cell-free systems. This has revealed distinct machineries for membrane budding and fission. Budding is mediated by clathrin and clathrin adaptors, whereas fission is mediated by dynamin and its interacting protein SH3p4, a lysophosphatidic acid acyl transferase.
Topics: Animals; Cytosol; Humans; Neurons; Synaptic Membranes; Synaptic Vesicles
PubMed: 10611977
DOI: 10.1146/annurev.cellbio.15.1.733 -
Current Opinion in Cell Biology Feb 2023In eukaryotic cells, the budding and fusion of intracellular transport vesicles is carefully orchestrated in space and time. Locally, a vesicle's source compartment, its... (Review)
Review
In eukaryotic cells, the budding and fusion of intracellular transport vesicles is carefully orchestrated in space and time. Locally, a vesicle's source compartment, its cargo, and its destination compartment are controlled by dynamic multi-protein specificity modules. Globally, vesicle constituents must be recycled to ensure homeostasis of compartment compositions. The emergence of a novel vesicle pathway therefore requires new specificity modules as well as new recycling routes. Here, we review recent research on local (molecular) constraints on gene module duplication and global (cellular) constraints on intracellular recycling. By studying the evolution of vesicle traffic, we may discover general principles of how complex traits arise via multiple intermediate steps.
Topics: Organelles; Transport Vesicles; Biological Transport; Eukaryotic Cells; Proteins
PubMed: 36610080
DOI: 10.1016/j.ceb.2022.102151 -
Methods in Molecular Biology (Clifton,... 2022Synaptic vesicle exocytosis can be monitored with genetically encoded pH sensors in an in vitro fluorescence microscopy setup. Here, we describe a workflow starting with...
Synaptic vesicle exocytosis can be monitored with genetically encoded pH sensors in an in vitro fluorescence microscopy setup. Here, we describe a workflow starting with preparation of a primary cell culture to eventually estimate synaptic vesicle pool sizes based on electrical current-evoked vesicle release, which is reported by the synaptobrevin 2-EGFP fusion protein synapto-pHluorin (spH) that is expressed inside the synaptic vesicle membrane. The readily releasable pool and the recycling pool of synaptic vesicles are released separately in response to electrical stimulation. As vesicle reacidification is blocked in this experimental design, every released vesicle is counted only once. This spH-based approach offers different information than styryl-dye (FM dyes)-based approaches because the total synaptic pool size is measured by an alkalinization step. This provides a normalization constant for quantifying and comparing the synaptic vesicle pool sizes. In addition to investigation of basic research questions, spH-reported vesicle release is valuable to determine presynaptic effects of, e.g., pharmacological drug treatments.
Topics: Exocytosis; Green Fluorescent Proteins; Microscopy, Fluorescence; Synaptic Transmission; Synaptic Vesicles
PubMed: 35099800
DOI: 10.1007/978-1-0716-1916-2_14 -
F1000Research 2017Synaptic vesicle recycling is essential for sustained and reliable neurotransmission. A key component of synaptic vesicle recycling is the synaptic vesicle biogenesis... (Review)
Review
Synaptic vesicle recycling is essential for sustained and reliable neurotransmission. A key component of synaptic vesicle recycling is the synaptic vesicle biogenesis process that is observed in synapses and that maintains the molecular identity of synaptic vesicles. However, the mechanisms by which synaptic vesicles are retrieved and reconstituted after fusion remain unclear. The complex molecular composition of synaptic vesicles renders their rapid biogenesis a daunting task. Therefore, in this context, kiss-and-run type transient fusion of synaptic vesicles with the plasma membrane without loss of their membrane composition and molecular identity remains a viable hypothesis that can account for the fidelity of the synaptic vesicle cycle. In this article, we discuss the biological implications of this problem as well as its possible molecular solutions.
PubMed: 29034086
DOI: 10.12688/f1000research.12072.1 -
Mini Reviews in Medicinal Chemistry 2017In plants, vesicle transport occurs in the secretory pathway in the cytosol, between the membranes of different compartments. Several protein components have been... (Review)
Review
BACKGROUND
In plants, vesicle transport occurs in the secretory pathway in the cytosol, between the membranes of different compartments. Several protein components have been identified to be involved in the process and their functions were characterized. Both cargos and other molecules (such as hormones) have been shown to use vesicle transport, although the major constituents of vesicles are lipids which are transferred from donor to acceptor membranes. In humans, malfunction of the cytosolic vesicle transport system leads to different diseases.
METHOD
To better understand and ultimately cure these human diseases, studying other model systems such as yeast can be beneficial. Plants with their cytosolic vesicle transport system could serve as another model system. However, this review focuses on plant vesicles not present in the cytosol but in the chloroplasts, where lipids produced in the surrounding envelope are transported through the aqueous stroma to the thylakoid membranes. Although chloroplast vesicles have found both biochemical and ultrastructural support, only two proteins have been characterized as components of the pathway. However, using bioinformatics a number of other proteins have been suggested as homologs to the cytosolic system.
RESULTS & CONCLUSION
Based on these findings vesicles of chloroplasts are likely most similar to the vesicles trafficking from ER to Golgi, or may even be unique, but important experimental support is yet lacking. In this review, proposed vesicle transport components in chloroplasts are presented, and their possible future implementation for human medicine is discussed.
Topics: Biological Transport; COP-Coated Vesicles; Chloroplasts; Choroideremia; Humans; Huntington Disease; Hypobetalipoproteinemias; Malabsorption Syndromes; Monomeric GTP-Binding Proteins; Plants; Plastids; SNARE Proteins; rab GTP-Binding Proteins
PubMed: 27599970
DOI: 10.2174/1389557516666160906102221 -
Frontiers in Cellular Neuroscience 2014The trigger for synaptic vesicle exocytosis is Ca(2+), which enters the synaptic bouton following action potential stimulation. However, spontaneous release of... (Review)
Review
The trigger for synaptic vesicle exocytosis is Ca(2+), which enters the synaptic bouton following action potential stimulation. However, spontaneous release of neurotransmitter also occurs in the absence of stimulation in virtually all synaptic boutons. It has long been thought that this represents exocytosis driven by fluctuations in local Ca(2+) levels. The vesicles responding to these fluctuations are thought to be the same ones that release upon stimulation, albeit potentially triggered by different Ca(2+) sensors. This view has been challenged by several recent works, which have suggested that spontaneous release is driven by a separate pool of synaptic vesicles. Numerous articles appeared during the last few years in support of each of these hypotheses, and it has been challenging to bring them into accord. We speculate here on the origins of this controversy, and propose a solution that is related to developmental effects. Constitutive membrane traffic, needed for the biogenesis of vesicles and synapses, is responsible for high levels of spontaneous membrane fusion in young neurons, probably independent of Ca(2+). The vesicles releasing spontaneously in such neurons are not related to other synaptic vesicle pools and may represent constitutively releasing vesicles (CRVs) rather than bona fide synaptic vesicles. In mature neurons, constitutive traffic is much dampened, and the few remaining spontaneous release events probably represent bona fide spontaneously releasing synaptic vesicles (SRSVs) responding to Ca(2+) fluctuations, along with a handful of CRVs that participate in synaptic vesicle turnover.
PubMed: 25538561
DOI: 10.3389/fncel.2014.00409