Definition of Munc13-homology-domains and characterization of a novel ubiquitously expressed Munc13 isoform

Munc13 proteins constitute a family of three highly homologous molecules (Munc13-1, Munc13-2 and Munc13-3). With the exception of a ubiquitously expressed Munc13-2 splice variant, Munc13 proteins are brain-specific. Munc13-1 has a central priming function in synaptic vesicle exocytosis from glutamatergic synapses. In order to identify Munc13-like proteins that may regulate secretory processes in non-glutamatergic neurons or non-neuronal cells, we developed protein profiles for two Munc13-homology-domains (MHDs). MHDs are present in a wide variety of proteins, some of which have previously been implicated in membrane trafficking reactions. Taking advantage of partial sequences in the human expressed sequence tag (EST) database, we characterized a novel, ubiquitously expressed, rat protein (Munc13-4) that belongs to a subfamily of Munc13-like molecules, in which the typical Munc13-like domain structure is conserved. Munc13-4 is predominantly expressed in lung where it is localized to goblet cells of the bronchial epithelium and to alveolar type II cells, both of which are cell types with secretory function. In the present study we identify a group of novel proteins, some of which may function in a Munc13-like manner to regulate membrane trafficking. The MHD profiles described in the present study are useful tools for the identification of Munc13-like proteins, that would otherwise have remained undetected.

Download Full-text

Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons

10.1101/175836 ◽

2017 ◽

Author(s):

Donovan Ventimiglia ◽

Cornelia I. Bargmann

Keyword(s):

Synaptic Vesicle ◽

Neuronal Cell ◽

Cell Types ◽

Snare Complex ◽

C Elegans ◽

Synaptic Vesicle Exocytosis ◽

High Calcium ◽

Vesicle Exocytosis ◽

Synaptic Dynamics

AbstractSynaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Exocytosis and retrieval each have two timescales in AWCON but one major timescale in ASH. Strong stimuli that elicit high calcium levels also increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.

Download Full-text

A Hint on the COVID-19 Risk: Population Disparities in Gene Expression of Three Receptors of SARS-CoV

10.20944/preprints202002.0408.v1 ◽

2020 ◽

Cited By ~ 11

Author(s):

Guoshuai Cai ◽

Xiang Cui ◽

Xia Zhu ◽

Jun Zhou

Keyword(s):

Gene Expression ◽

Bronchial Epithelium ◽

Cell Types ◽

Normal Lung ◽

Alveolar Type ◽

Significant Difference ◽

Former Smokers ◽

Novel Coronavirus ◽

Gender Groups ◽

Different Cell Types

The current spreading novel coronavirus SARS-CoV-2 is highly infectious and pathogenic and has attracted global attention. Recent studies have found that SARS-CoV-2 and SARS-CoV share around 80% of homology and use the same cell entry receptor, ACE2. These inspired us to study other receptors of SARS-CoV, which may be used for SARS-CoV-2 binding as well. In this study, we screened the gene expression of three receptors (ACE2, DC-SIGN and L-SIGN) in four datasets of normal lung tissue from lung adenocarcinoma patients and two single-cell RNA sequencing datasets from normal lung and bronchial epithelial cells separately. No significant difference in gene expression of these three receptors were found between gender groups (male vs female). We found higher gene expression of DC-SIGN in elder with age>60 and higher gene expression of L-SIGN in Caucasian than Asian. Similar to ACE2, we observed significantly higher DC-SIGN gene expression in the lungs of smokers, especially former smokers. However, smokers upregulate ACE2 and DC-SIGN gene expression in different cell types. In the whole lung, ACE2 is actively expressed in remodeled Alveolar Type II cells of former smokers, while DC-SIGN is largely expressed in monocytes of former smokers and dendritic cells of current smokers. In bronchial epithelium, no obvious gene expression of DC-SIGN and L-SIGN was observed while ACE2 was found to be actively expressed in goblet cells of current smokers and club cells of non-smokers. In conclusion, our findings may indicate that smokers, especially former smokers, and people over 60 have higher risk and are more susceptible to SARS-CoV-2 infection. Also, this study provides hints on possible SARS-CoV-2 pathogenicity mechanisms in lung infection.

Download Full-text

Secretory Granule Exocytosis

Physiological Reviews ◽

10.1152/physrev.00031.2002 ◽

2003 ◽

Vol 83 (2) ◽

pp. 581-632 ◽

Cited By ~ 562

Author(s):

Robert D. Burgoyne ◽

Alan Morgan

Keyword(s):

Secretory Granule ◽

Secretory Granules ◽

Physiological Role ◽

Cell Types ◽

Control Mechanisms ◽

Granule Exocytosis ◽

Synaptic Vesicle Exocytosis ◽

Wide Range ◽

Vesicle Exocytosis ◽

Protein Components

Regulated exocytosis of secretory granules or dense-core granules has been examined in many well-characterized cell types including neurons, neuroendocrine, endocrine, exocrine, and hemopoietic cells and also in other less well-studied cell types. Secretory granule exocytosis occurs through mechanisms with many aspects in common with synaptic vesicle exocytosis and most likely uses the same basic protein components. Despite the widespread expression and conservation of a core exocytotic machinery, many variations occur in the control of secretory granule exocytosis that are related to the specialized physiological role of particular cell types. In this review we describe the wide range of cell types in which regulated secretory granule exocytosis occurs and assess the evidence for the expression of the conserved fusion machinery in these cells. The signals that trigger and regulate exocytosis are reviewed. Aspects of the control of exocytosis that are specific for secretory granules compared with synaptic vesicles or for particular cell types are described and compared to define the range of accessory control mechanisms that exert their effects on the core exocytotic machinery.

Download Full-text

Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons

eLife ◽

10.7554/elife.31234 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 6

Author(s):

Donovan Ventimiglia ◽

Cornelia I Bargmann

Keyword(s):

Synaptic Vesicle ◽

Neuronal Cell ◽

Cell Types ◽

Snare Complex ◽

C Elegans ◽

Synaptic Vesicle Exocytosis ◽

High Calcium ◽

Vesicle Exocytosis ◽

Synaptic Dynamics

Synaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Strong stimuli that elicit high calcium levels increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.

Download Full-text

Synaptotagmin VII Regulates Ca2+-Dependent Exocytosis of Lysosomes in Fibroblasts

The Journal of Cell Biology ◽

10.1083/jcb.148.6.1141 ◽

2000 ◽

Vol 148 (6) ◽

pp. 1141-1150 ◽

Cited By ~ 206

Author(s):

Iñigo Martinez ◽

Sabyasachi Chakrabarti ◽

Turid Hellevik ◽

Jennifer Morehead ◽

Kimberly Fowler ◽

...

Keyword(s):

Synaptic Vesicle ◽

Rat Kidney ◽

Transmembrane Proteins ◽

Cell Types ◽

C2 Domains ◽

Synaptic Vesicle Exocytosis ◽

Vesicle Exocytosis ◽

Normal Rat ◽

Recombinant Fragments ◽

C2a Domain

Synaptotagmins (Syts) are transmembrane proteins with two Ca2+-binding C2 domains in their cytosolic region. Syt I, the most widely studied isoform, has been proposed to function as a Ca2+ sensor in synaptic vesicle exocytosis. Several of the twelve known Syts are expressed primarily in brain, while a few are ubiquitous (Sudhof, T.C., and J. Rizo. 1996. Neuron. 17: 379–388; Butz, S., R. Fernandez-Chacon, F. Schmitz, R. Jahn, and T.C. Sudhof. 1999. J. Biol. Chem. 274:18290–18296). The ubiquitously expressed Syt VII binds syntaxin at free Ca2+ concentrations ([Ca2+]) below 10 μM, whereas other isoforms require 200–500 μM [Ca2+] or show no Ca2+-dependent syntaxin binding (Li, C., B. Ullrich, Z. Zhang, R.G.W. Anderson, N. Brose, and T.C. Sudhof. 1995. Nature. 375:594–599). We investigated the involvement of Syt VII in the exocytosis of lysosomes, which is triggered in several cell types at 1–5 μM [Ca2+] (Rodríguez, A., P. Webster, J. Ortego, and N.W. Andrews. 1997. J. Cell Biol. 137:93–104). Here, we show that Syt VII is localized on dense lysosomes in normal rat kidney (NRK) fibroblasts, and that GFP-tagged Syt VII is targeted to lysosomes after transfection. Recombinant fragments containing the C2A domain of Syt VII inhibit Ca2+-triggered secretion of β-hexosaminidase and surface translocation of Lgp120, whereas the C2A domain of the neuronal- specific isoform, Syt I, has no effect. Antibodies against the Syt VII C2A domain are also inhibitory in both assays, indicating that Syt VII plays a key role in the regulation of Ca2+-dependent lysosome exocytosis.

Download Full-text

Faculty Opinions recommendation of STED microscopy reveals that synaptotagmin remains clustered after synaptic vesicle exocytosis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1032017.370874 ◽

2006 ◽

Author(s):

Lennart Brodin

Keyword(s):

Synaptic Vesicle ◽

Sted Microscopy ◽

Synaptic Vesicle Exocytosis ◽

Vesicle Exocytosis

Download Full-text

Faculty Opinions recommendation of Profilin2 contributes to synaptic vesicle exocytosis, neuronal excitability, and novelty-seeking behavior.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1090362.543612 ◽

2007 ◽

Author(s):

Carol Otey

Keyword(s):

Synaptic Vesicle ◽

Neuronal Excitability ◽

Novelty Seeking ◽

Synaptic Vesicle Exocytosis ◽

Seeking Behavior ◽

Vesicle Exocytosis

Download Full-text

Faculty Opinions recommendation of Tilting the balance between facilitatory and inhibitory functions of mammalian and Drosophila Complexins orchestrates synaptic vesicle exocytosis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1168432.630615 ◽

2009 ◽

Author(s):

Jakob Soerensen

Keyword(s):

Synaptic Vesicle ◽

Synaptic Vesicle Exocytosis ◽

Vesicle Exocytosis

Download Full-text

Genetic analysis of amyotrophic lateral sclerosis identifies contributing pathways and cell types

Science Advances ◽

10.1126/sciadv.abd9036 ◽

2021 ◽

Vol 7 (3) ◽

pp. eabd9036

Author(s):

Sara Saez-Atienzar ◽

Sara Bandres-Ciga ◽

Rebekah G. Langston ◽

Jonggeol J. Kim ◽

Shing Wan Choi ◽

...

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Membrane Trafficking ◽

Molecular Mechanisms ◽

Cell Types ◽

Polygenic Risk Score ◽

Genome Wide ◽

Genome Wide Data ◽

Data Driven Approach ◽

Single Nucleus ◽

Lateral Sclerosis

Despite the considerable progress in unraveling the genetic causes of amyotrophic lateral sclerosis (ALS), we do not fully understand the molecular mechanisms underlying the disease. We analyzed genome-wide data involving 78,500 individuals using a polygenic risk score approach to identify the biological pathways and cell types involved in ALS. This data-driven approach identified multiple aspects of the biology underlying the disease that resolved into broader themes, namely, neuron projection morphogenesis, membrane trafficking, and signal transduction mediated by ribonucleotides. We also found that genomic risk in ALS maps consistently to GABAergic interneurons and oligodendrocytes, as confirmed in human single-nucleus RNA-seq data. Using two-sample Mendelian randomization, we nominated six differentially expressed genes (ATG16L2, ACSL5, MAP1LC3A, MAPKAPK3, PLXNB2, and SCFD1) within the significant pathways as relevant to ALS. We conclude that the disparate genetic etiologies of this fatal neurological disease converge on a smaller number of final common pathways and cell types.

Download Full-text