Action of Clostridial Neurotoxins and Mechanism of the Membrane Fusion of Intracellular Transport Vesicles.

AbstractDirected transport of transmembrane proteins is generally believed to occur via intracellular transport vesicles. However, using single particle tracking in rat hippocampal neurons with a pH-sensitive quantum dot probe which specifically reports surface movement of receptors, we have identified a subpopulation of neuronal EphB2 receptors that exhibit directed motion between synapses within the plasma membrane itself. This receptor movement occurs independently of the cytoskeleton but is dependent on cholesterol and is regulated by neuronal activity.

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Reconstitution in vitro of a membrane-fusion event involved in constitutive exocytosis. A role for cytosolic proteins and a GTP-binding protein, but not for Ca2+

Biochemical Journal ◽

10.1042/bj2850383 ◽

1992 ◽

Vol 285 (2) ◽

pp. 383-385 ◽

Cited By ~ 6

Author(s):

J M Edwardson ◽

P U Daniels-Holgate

Keyword(s):

Membrane Fusion ◽

Binding Protein ◽

Fusion Event ◽

Gtp Binding Protein ◽

In Vitro System ◽

Cytosolic Proteins ◽

Golgi Transport ◽

Gtp Binding ◽

Transport Vesicles

The fusion of post-Golgi transport vesicles with the plasma membrane is perhaps the least well understood step in the network of intracellular membrane traffic. We have used an ‘in vitro’ system to study this membrane-fusion event. We show here that fusion requires the presence of cytosolic proteins, but not Ca2+, and is inhibited by the non-hydrolysable GTP analogue guanosine 5′-[gamma-thio]triphosphate, which indicates the involvement of a GTP-binding protein.

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Functional characterisation of tetanus and botulinum neurotoxins binding domains

Journal of Cell Science ◽

10.1242/jcs.112.16.2715 ◽

1999 ◽

Vol 112 (16) ◽

pp. 2715-2724 ◽

Cited By ~ 1

Author(s):

G. Lalli ◽

J. Herreros ◽

S.L. Osborne ◽

C. Montecucco ◽

O. Rossetto ◽

...

Keyword(s):

Intracellular Transport ◽

Specific Binding ◽

Dependent Manner ◽

Heavy Chains ◽

Binding Domains ◽

Functional Characterisation ◽

Clostridial Neurotoxins ◽

Botulinum Neurotoxins ◽

Carboxy Terminal ◽

Recombinant Fragments

Tetanus and botulinum neurotoxins constitute a family of bacterial protein toxins responsible for two deadly syndromes in humans (tetanus and botulism, respectively). They bind with high affinity to neurons wherein they cause a complete inhibition of evoked neurotransmitter release. Here we report on the cloning, expression and use of the recombinant fragments of the heavy chains of tetanus neurotoxin and botulinum neurotoxin serotypes A, B and E as tools to study the neurospecific binding of the holotoxins. We found that the recombinant 50 kDa carboxy-terminal domains of tetanus and botulinum neurotoxins alone are responsible for the specific binding and internalisation into spinal cord cells in culture. Moreover, we provide evidence that the recombinant fragments block the internalization of the parental holotoxins in a dose-dependent manner, as determined by following the neurotoxin-dependent cleavage of their targets VAMP/synaptobrevin and SNAP-25. In addition, the recombinant binding fragments cause a significant delay in the paralysis induced by the corresponding holotoxin on the mouse phrenic nerve-hemidiaphragm preparation. Taken together, these results show that the carboxy-terminal domain of tetanus and botulinum neurotoxins is necessary and sufficient for the binding and internalisation of these proteins in neurons and open the possibility to use them as tools for the functional characterisation of the intracellular transport of clostridial neurotoxins.

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Rab GDI: a solubilizing and recycling factor for rab9 protein.

Molecular Biology of the Cell ◽

10.1091/mbc.4.4.425 ◽

1993 ◽

Vol 4 (4) ◽

pp. 425-434 ◽

Cited By ~ 103

Author(s):

T Soldati ◽

M A Riederer ◽

S R Pfeffer

Keyword(s):

Complex Formation ◽

Intracellular Transport ◽

Rab Proteins ◽

Rab Protein ◽

Transport Vesicles ◽

Late Endosomes ◽

Geranylgeranyl Transferase ◽

Carboxy Terminal ◽

Golgi Network

Rab proteins are thought to function in the processes by which transport vesicles identify and/or fuse with their respective target membranes. The bulk of these proteins are membrane associated, but a measurable fraction can be found in the cytosol. The cytosolic forms of rab3A, rab11, and Sec4 occur as equimolar complexes with a class of proteins termed "GDIs," or "GDP dissociation inhibitors." We show here that the cytosolic form of rab9, a protein required for transport between late endosomes and the trans Golgi network, also occurs as a complex with a GDI-like protein, with an apparent mass of approximately 80 kD. Complex formation could be reconstituted in vitro using recombinant rab9 protein, cytosol, ATP, and geranylgeranyl diphosphate, and was shown to require an intact rab9 carboxy terminus, as well as rab9 geranylgeranylation. Monoprenylation was sufficient for complex formation because a mutant rab9 protein bearing the carboxy terminal sequence, CLLL, was prenylated in vitro by geranylgeranyl transferase I and was efficiently incorporated into 80-kD complexes. Purified, prenylated rab9 could also assemble into 80-kD complexes by addition of purified, rab3A GDI. Finally, rab3A-GDI had the capacity to solubilize rab9GDP, but not rab9GTP, from cytoplasmic membranes. These findings support the proposal that GDI proteins serve to recycle rab proteins from their target membranes after completion of a rab protein-mediated, catalytic cycle. Thus GDI proteins have the potential to regulate the availability of specific intracellular transport factors.

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A New Syntaxin Family Member Implicated in Targeting of Intracellular Transport Vesicles

Journal of Biological Chemistry ◽

10.1074/jbc.271.30.17961 ◽

1996 ◽

Vol 271 (30) ◽

pp. 17961-17965 ◽

Cited By ~ 101

Author(s):

Jason B. Bock ◽

Richard C. Lin ◽

Richard H. Scheller

Keyword(s):

Family Member ◽

Intracellular Transport ◽

Transport Vesicles

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Novel syntaxin homologue, Pep12p, required for the sorting of lumenal hydrolases to the lysosome-like vacuole in yeast.

Molecular Biology of the Cell ◽

10.1091/mbc.7.4.579 ◽

1996 ◽

Vol 7 (4) ◽

pp. 579-594 ◽

Cited By ~ 203

Author(s):

K A Becherer ◽

S E Rieder ◽

S D Emr ◽

E W Jones

Keyword(s):

Intracellular Transport ◽

Sequence Similarity ◽

Integral Membrane Protein ◽

Subcellular Fractionation ◽

Hydrophobic Region ◽

Significant Sequence Similarity ◽

Transport Vesicles ◽

Class D ◽

A Minor ◽

35 Kda Protein

pep12/vps6 mutants of Saccharomyces cerevisiae are defective in delivery of soluble vacuolar hydrolases to the vacuole. Morphological analysis by electron microscopy revealed that pep12 cells accumulate 40- to 50-nm vesicles. Furthermore, pep12 cells have enlarged vacuoles characteristic of class D pep/vps mutants. PEP12 encodes a protein of 288 amino acids that has a C-terminal hydrophobic region and shares significant sequence similarity with members of the syntaxin protein family. These proteins appear to participate in the docking and fusion of intracellular transport vesicles. Pep12p is the first member of the syntaxin family to be implicated in transport between the Golgi and the vacuole/lysosome. Pep12p-specific polyclonal antisera detected a 35-kDa protein that fractionated as an integral membrane protein. Subcellular fractionation experiments revealed that Pep12p was associated with membrane fractions of two different densities; the major pool (approximately 90%) of pep12p may associate with the endosome, while a minor pool (approximately 10%) cofractionated with the late Golgi marker Kex2p. These observations suggest that Pep12p may mediate the docking of Golgi-derived transport vesicles at the endosome.

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Tumor protein D54 defines a new class of intracellular transport vesicles

The Journal of Cell Biology ◽

10.1083/jcb.201812044 ◽

2019 ◽

Vol 219 (1) ◽

Cited By ~ 5

Author(s):

Gabrielle Larocque ◽

Penelope J. La-Borde ◽

Nicholas I. Clarke ◽

Nicholas J. Carter ◽

Stephen J. Royle

Keyword(s):

Membrane Trafficking ◽

Intracellular Transport ◽

Super Resolution ◽

Molecular Heterogeneity ◽

Rab Gtpases ◽

New Class ◽

Transport Vesicles ◽

Transport Vesicle ◽

Membrane Compartment ◽

Generic Class

Transport of proteins and lipids from one membrane compartment to another is via intracellular vesicles. We investigated the function of tumor protein D54 (TPD54/TPD52L2) and found that TPD54 was involved in multiple membrane trafficking pathways: anterograde traffic, recycling, and Golgi integrity. To understand how TPD54 controls these diverse functions, we used an inducible method to reroute TPD54 to mitochondria. Surprisingly, this manipulation resulted in the capture of many small vesicles (30 nm diameter) at the mitochondrial surface. Super-resolution imaging confirmed the presence of similarly sized TPD54-positive structures under normal conditions. It appears that TPD54 defines a new class of transport vesicle, which we term intracellular nanovesicles (INVs). INVs meet three criteria for functionality. They contain specific cargo, they have certain R-SNAREs for fusion, and they are endowed with a variety of Rab GTPases (16 out of 43 tested). The molecular heterogeneity of INVs and the diverse functions of TPD54 suggest that INVs have various membrane origins and a number of destinations. We propose that INVs are a generic class of transport vesicle that transfer cargo between these varied locations.

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Faculty Opinions recommendation of Tumor protein D54 defines a new class of intracellular transport vesicles.

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

10.3410/f.736836613.793567033 ◽

2019 ◽

Author(s):

Robert Parton

Keyword(s):

Intracellular Transport ◽

New Class ◽

Transport Vesicles

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Adaptins

Molecular Biology of the Cell ◽

10.1091/mbc.12.10.2907 ◽

2001 ◽

Vol 12 (10) ◽

pp. 2907-2920 ◽

Cited By ~ 288

Author(s):

Markus Boehm ◽

Juan S. Bonifacino

Keyword(s):

Arabidopsis Thaliana ◽

Intracellular Transport ◽

Adaptor Protein ◽

Fruit Fly ◽

C Elegans ◽

Transport Vesicles ◽

Intron Structure ◽

Related Proteins ◽

Selection Of ◽

Plant Arabidopsis Thaliana

Adaptins are subunits of adaptor protein (AP) complexes involved in the formation of intracellular transport vesicles and in the selection of cargo for incorporation into the vesicles. In this article, we report the results of a survey for adaptins from sequenced genomes including those of man, mouse, the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, the plant Arabidopsis thaliana, and the yeasts, Saccharomyces cerevisiae andSchizosaccharomyces pombe. We find that humans, mice, and Arabidopsis thaliana have four AP complexes (AP-1, AP-2, AP-3, and AP-4), whereas D. melanogaster,C. elegans, S. cerevisiae, and S. pombe have only three (AP-1, AP-2, and AP-3). Additional diversification of AP complexes arises from the existence of adaptin isoforms encoded by distinct genes or resulting from alternative splicing of mRNAs. We complete the assignment of adaptins to AP complexes and provide information on the chromosomal localization, exon-intron structure, and pseudogenes for the different adaptins. In addition, we discuss the structural and evolutionary relationships of the adaptins and the genetic analyses of their function. Finally, we extend our survey to adaptin-related proteins such as the GGAs and stonins, which contain domains homologous to the adaptins.

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Prm1 Targeting to Contact Sites Enhances Fusion during Mating in Saccharomyces cerevisiae

Eukaryotic Cell ◽

10.1128/ec.00116-10 ◽

2010 ◽

Vol 9 (10) ◽

pp. 1538-1548 ◽

Cited By ~ 10

Author(s):

Valerie N. Olmo ◽

Eric Grote

Keyword(s):

Saccharomyces Cerevisiae ◽

Plasma Membrane ◽

Membrane Fusion ◽

Intracellular Transport ◽

Plasma Membranes ◽

Yeast Cells ◽

Fusion Event ◽

Mating Activity ◽

Content Type ◽

Contact Sites

ABSTRACT Prm1 is a pheromone-regulated membrane glycoprotein involved in the plasma membrane fusion event of Saccharomyces cerevisiae mating. Although this function suggests that Prm1 should act at contact sites in pairs of mating yeast cells where plasma membrane fusion occurs, only a small percentage of the total Prm1 was actually detected on the plasma membrane. We therefore investigated the intracellular transport of Prm1 and how this transport contributes to cell fusion. Two Prm1 chimeras that were sorted away from the contact site had reduced fusion activity, indicating that Prm1 indeed functions at contact sites. However, most Prm1 is located in endosomes and other cytoplasmic organelles and is targeted to vacuoles for degradation. Mutations in a putative endocytosis signal in a cytoplasmic loop partially stabilized the Prm1 protein and caused it to accumulate on the plasma membrane, but this endocytosis mutant actually had reduced mating activity. When Prm1 was expressed from a galactose-regulated promoter and its synthesis was repressed at the start of mating, vanishingly small amounts of Prm1 protein remained at the time when the plasma membranes came into contact. Nevertheless, this stable pool of Prm1 was retained at polarized sites on the plasma membrane and was sufficient to promote plasma membrane fusion. Thus, the amount of Prm1 expressed in mating yeast is far in excess of the amount required to facilitate fusion.

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