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Introduction to botulinum toxin
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
Botulinum toxin is a proteolytic enzyme which functions by inhibiting the secretion of acetylcholine from afferent neurons at the neuromuscular junction. The toxin binds to the cell membrane of neurons which then form a vesicle around it to absorb it across the cell membrane through a process known as endocytosis. As the vesicle is taken through the cell membrane, the contents acidify, causing the vesicle to migrate further within the cell. Once the toxin is within the cytoplasm of an acetylcholine-secreting neurons, it cleaves soluble NSF attachment protein receptors, otherwise known as SNARE proteins. These proteins are essential in the exocytosis of vesicles and their contents from the presynaptic membrane into the presynaptic cleft. By irreversibly inhibiting the exocytosis of acetylcholine, botulinum toxin prevents neurons in the affected area from initiating movement at motor muscle endplates. In the realm of cosmetics, this prevents muscular movement and wrinkle formation.
Homeostasis of Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
The SNARE complex is formed by members of the synaptosomal-associated protein 25 (SNAP-25), vesicle-associated membrane protein (VAMP) and members of the syntaxins family. Interactions between these proteins create a four-helix bundle, formed by two helices of SNAP-25, one vesicular-transmembrane VAMP and one presynaptic plasma membrane syntaxin that brings together the vesicular and plasmatic membranes. Other proteins that interact with the SNARE complex include Munc-18, complexin, synaptophysin, and synaptotagmin [77]. In addition, synaptotagmin serves as a calcium sensor and regulates the SNARE zipping. The SM proteins are evolutionary conserved cytosolic proteins that serve as essential partners for SNARE proteins in fusion. Among these is Munc 18, which primarily interacts with syntaxin-1 and whose function is tightly regulated by calcium.
Orthopaedic Pharmacology
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Manoj Ramachandran, Daud Chou, Natasha Rahman
Botulinum toxin is a protein produced by Clostridium botulinum, which can be used as a very potent therapeutic neurotoxin causing muscle weakness. The toxin enters the axon terminals and degrades the SNAP-25 protein, a type of SNARE protein required for vesicle fusion. This prevents neurosecretory vesicles from docking with the nerve synapse plasma membrane and releasing their neurotransmitters. In orthopaedics, botulinum toxin is used in the treatment of movement disorders associated with injury or disease of the CNS including cerebral palsy and trauma.
The neurosciences at the Max Planck Institute for Biophysical Chemistry in Göttingen
Published in Journal of the History of the Neurosciences, 2023
The early 1990s were the “golden years” for the discovery of proteins, which play a decisive role in binding vesicles to the outer cell membrane and in the subsequent fusion and secretion (Südhof 2014). Three groups made significant contributions here, with different model systems and working methods. James E. Rothman and colleagues studied intracellular vesicle transport in a cell-free assay with the biochemical method. They found NSF, SNAP, and named the proteins that are involved in binding the vesicle to the cell membrane the SNARE complex (Söllner et al. 1993). Randy W. Schekman and his colleagues used genetic screens to study yeast mutants in which the secretion was impaired. They cloned the corresponding gene and discovered the biochemical reactions that play a role in secretion. Thomas C. Südhof, Pietro de Camilli, and Reinhard Jahn researched the proteins that control the fusion of the vesicles with the cell membrane in nerve cells, contributing to the release of neurotransmitters using biochemical, genetic, physiological, and electron-microscopic methods. All three groups discovered similar proteins and mechanisms, which shows that secretion is an evolutionarily old and conserved mechanism (Bennett and Scheller 1993).
Inhibiting extracellular vesicles formation and release: a review of EV inhibitors
Published in Journal of Extracellular Vesicles, 2020
Mariadelva Catalano, Lorraine O’Driscoll
When MVBs are formed, as mentioned above, they can either fuse with lysosomes or result in exosomes release via fusion with the cell membrane. Their transport within cells and towards the cell membrane is dependent on interaction with actin and microtubules of the cytoskeleton and is regulated by many proteins. Particularly important here is the GTPase family of Rab proteins, although their involvement seems to be somewhat cell specific. For example, both Rab27a and Rab27b have been shown to be involved in exosomes release from HeLa cells, i.e. Rab27b regulates the motility of MVBs towards the cell membrane and Rab27a promotes their fusion. However, Rab27 isoforms are not ubiquitous. Thus, other cell types seem to regulate exosomes release using different Rab proteins, such as Rab11 in K562 cells (bone marrow chronic myelogenous leukaemia cells) and Rab35 in Oli-neu cells (oligodendroglial cell lines) [18–20]. SNARE (Soluble NSF Attachment Protein REceptor) protein family members are also involved in orchestrating the final exosomes release in response to membrane fusion. This is achieved through the formation of a SNARE complex composed of three-fourth coiled-coil helices proteins. SNARE activity is partially controlled by the phosphorylation state of these proteins, which influences their localisation and their interaction with SNARE partners, thus contributing to regulated exosomes release [21–23].
Relationship between the effect of polyunsaturated fatty acids (PUFAs) on brain plasticity and the improvement on cognition and behavior in individuals with autism spectrum disorder
Published in Nutritional Neuroscience, 2022
Isabel Barón-Mendoza, Aliesha González-Arenas
Vesicle trafficking is mainly regulated by SNARE (Soluble NSF Attachment Protein) proteins [131]. SNARE proteins are at vesicle membranes (v-SNAREs) as in target membranes (t-SNAREs). v-SNARE and t-SNARE pairing promotes the fusion of membranes by using the energy released during the formation of a trans-SNARE complex, which consists of a four α helix beam that allows the narrow approaching of membranes for the beginning of the fusion [132]. The specificity of this fusion mechanism is supported by the vesicle addressing to the target membrane by Rab proteins. Rab proteins are monomeric GTPases, which in its GTP-bound active state guide a vesicle to a specific target membrane for its following fusion [133].