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Juranek JK, Mukherjee K, Jahn R, Li JY. Coordinated bi-directional trafficking of synaptic vesicle and active zone proteins in peripheral nerves. Biochem Biophys Res Commun 2021; 559:92-98. [PMID: 33933994 DOI: 10.1016/j.bbrc.2021.04.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 11/18/2022]
Abstract
Synaptic transmission is mediated by neurotransmitters that are stored in synaptic vesicles (SV) and released at the synaptic active zone (AZ). While in recent years major progress has been made in unraveling the molecular machinery responsible for SV docking, fusion and exocytosis, the mechanisms governing AZ protein and SV trafficking through axons still remain unclear. Here, we performed stop-flow nerve ligation to examine axonal trafficking of endogenous AZ and SV proteins. Rat sciatic nerves were collected 1 h, 3 h and 8 h post ligation and processed for immunohistochemistry and electron microscopy. First, we followed the transport of an integral synaptic vesicle protein, SV2A and a SV-associated protein involved in SV trafficking, Rab3a, and observed that while SV2A accumulated on both sides of ligation, Rab3a was only noticeable in the proximal segment of the ligated nerve indicating that only SV trans-membrane protein SV2A displayed a bi-directional axonal transport. We then demonstrate that multiple AZ proteins accumulate rapidly on either side of the ligation with a timescale similar to that of SV2A. Overall, our data uncovers an unexpected robust bi-directional, coordinated -trafficking of SV and AZ proteins in peripheral nerves. This implies that pathological disruption of axonal trafficking will not only impair trafficking of newly synthesized proteins to the synapse but will also affect retrograde transport, leading to neuronal dysfunction and likely neurodegeneration.
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Affiliation(s)
- Judyta K Juranek
- Wallenberg Neuroscience Center, Lund University Biomedical Center, Lund, Sweden.
| | - Konark Mukherjee
- Fralin Biomedical Research Institute, Virginia Tech Carilion School of Medicine, Blacksburg, VA, USA
| | - Reinhard Jahn
- Dept. of Neurobiology, Max Planck Institute for Biophysical Chemistry, Goettingen, Germany
| | - Jia-Yi Li
- Wallenberg Neuroscience Center, Lund University Biomedical Center, Lund, Sweden.
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Piccolo is essential for the maintenance of mouse retina but not cochlear hair cell function. Aging (Albany NY) 2021; 13:11678-11695. [PMID: 33882456 PMCID: PMC8109093 DOI: 10.18632/aging.202861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/16/2021] [Indexed: 12/14/2022]
Abstract
Piccolo is a presynaptic protein with high conservation among different species, and the expression of Piccolo is extensive in vertebrates. Recently, a small fragment of Piccolo (Piccolino), arising due to the incomplete splicing of intron 5/6, was found to be present in the synapses of retinas and cochleae. However, the comprehensive function of Piccolo in the retina and cochlea remains unclear. In this study, we generated Piccolo knockout mice using CRISPR-Cas9 technology to explore the function of Piccolo. Unexpectedly, whereas no abnormalities were found in the cochlear hair cells of the mutant mice, significant differences were found in the retinas, in which two layers (the outer nuclear layer and the outer plexiform layer) were absent. Additionally, the amplitudes of electroretinograms were significantly reduced and pigmentation was observed in the fundoscopy of the mutant mouse retinas. The expression levels of Bassoon, a homolog of Piccolo, as well as synapse-associated proteins CtBP1, CtBP2, Kif3A, and Rim1 were down-regulated. The numbers of ribbon synapses in the retinas of the mutant mice were also reduced. Altogether, the phenotype of Piccolo-/- mice resembled the symptoms of retinitis pigmentosa (RP) in humans, suggesting Piccolo might be a candidate gene of RP and indicates Piccolo knockout mice are a good model for elucidating the molecular mechanisms of RP.
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Menéndez-Méndez A, Díaz-Hernández JI, Ortega F, Gualix J, Gómez-Villafuertes R, Miras-Portugal MT. Specific Temporal Distribution and Subcellular Localization of a Functional Vesicular Nucleotide Transporter (VNUT) in Cerebellar Granule Neurons. Front Pharmacol 2017; 8:951. [PMID: 29311945 PMCID: PMC5744399 DOI: 10.3389/fphar.2017.00951] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 12/15/2017] [Indexed: 12/14/2022] Open
Abstract
Adenosine triphosphate (ATP) is an important extracellular neurotransmitter that participates in several critical processes like cell differentiation, neuroprotection or axon guidance. Prior to its exocytosis, ATP must be stored in secretory vesicles, a process that is mediated by the Vesicular Nucleotide Transporter (VNUT). This transporter has been identified as the product of the SLC17A9 gene and it is prominently expressed in discrete brain areas, including the cerebellum. The main population of cerebellar neurons, the glutamatergic granule neurons, depends on purinergic signaling to trigger neuroprotective responses. However, while nucleotide receptors like P2X7 and P2Y13 are known to be involved in neuroprotection, the mechanisms that regulate ATP release in relation to such events are less clearly understood. In this work, we demonstrate that cerebellar granule cells express a functional VNUT that is involved in the regulation of ATP exocytosis. Numerous vesicles loaded with this nucleotide can be detected in these granule cells and are staining by the fluorescent ATP-marker, quinacrine. High potassium stimulation reduces quinacrine fluorescence in granule cells, indicating they release ATP via calcium dependent exocytosis. Specific subcellular markers were used to assess the localization of VNUT in granule cells, and the transporter was detected in both the axonal and somatodendritic compartments, most predominantly in the latter. However, co-localization with the specific lysosomal marker LAMP-1 indicated that VNUT can also be found in non-synaptic vesicles, such as lysosomes. Interestingly, the weak co-localization between VNUT and VGLUT1 suggests that the ATP and glutamate vesicle pools are segregated, as also observed in the cerebellar cortex. During post-natal cerebellar development, VNUT is found in granule cell precursors, co-localizing with markers of immature cells like doublecortin, suggesting that this transporter may be implicated in the initial stages of granule cell development.
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Affiliation(s)
- Aida Menéndez-Méndez
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
| | - Juan I Díaz-Hernández
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
| | - Felipe Ortega
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
| | - Javier Gualix
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
| | - Rosa Gómez-Villafuertes
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
| | - María T Miras-Portugal
- Department of Biochemistry and Molecular Biology, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain.,University Institute of Neurochemistry Research (IUIN), Complutense University of Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain
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