3fuq
Glycosylated SV2 and Gangliosides as Dual Receptors for Botulinum Neurotoxin Serotype F
Structural highlights
FunctionBXF_CLOBL Botulinum toxin causes flaccid paralysis by inhibiting neurotransmitter (acetylcholine) release from the presynaptic membranes of nerve terminals of the eukaryotic host skeletal and autonomic nervous system, with frequent heart or respiratory failure (PubMed:14423425). Precursor of botulinum neurotoxin F which may have 2 coreceptors; complex polysialylated gangliosides found on neural tissue and specific membrane-anchored proteins found in synaptic vesicles. Receptor proteins are exposed on host presynaptic cell membrane during neurotransmitter release, when the toxin heavy chain (HC) binds to them (PubMed:19476346, PubMed:19650874). Upon synaptic vesicle recycling the toxin is taken up via the endocytic pathway. When the pH of the toxin-containing endosome drops a structural rearrangement occurs so that the N-terminus of the HC forms pores that allows the light chain (LC) to translocate into the cytosol. Once in the cytosol the disulfide bond linking the 2 subunits is reduced and LC cleaves its target protein on synaptic vesicles, preventing their fusion with the cytoplasmic membrane and thus neurotransmitter release (By similarity). Requires complex gangliosides for full neurotoxicity (PubMed:19650874, PubMed:21483489). Electrical stimulation increases uptake of toxin, presumably by transiently exposing a receptor usually found in eukaryotic target synaptic vesicles (PubMed:19476346, PubMed:19650874). Blocks neurotransitter release by cleaving synaptobrevin-2/VAMP2 (PubMed:19476346). It is not clear whether a synaptic vesicle protein acts as its receptor; there is evidence for and against SV2 fulfilling this function (PubMed:19650874, PubMed:21483489, PubMed:19476346).[UniProtKB:P0DPI0][1] [2] [3] [4] Has protease activity (PubMed:19476346, PubMed:19543288). After translocation into the eukaryotic host cytosol, inhibits neurotransmitter release by acting as a zinc endopeptidase that catalyzes the hydrolysis of the '58-Gln-|-Lys-59' bond of synaptobrevin-2/VAMP2 and probably also the equivalent 'Gln-|-Lys' sites in VAMP1 and VAMP3 (PubMed:19476346, PubMed:19543288). Substrate specificity is conferred by multiple interactions of LC with substrate (PubMed:19543288).[UniProtKB:P30996][5] [6] Responsible for host epithelial cell transcytosis, host nerve cell targeting and translocation of light chain (LC) into host cytosol. Composed of 3 subdomains; the translocation domain (TD), and N-terminus and C-terminus of the receptor-binding domain (RBD). The RBD is responsible for the adherence of the toxin to the cell surface (PubMed:19476346, PubMed:19650874). The N-terminus of the TD wraps an extended belt around the perimeter of the LC, protecting Zn(2+) in the active site; it may also prevent premature LC dissociation from the translocation channel and protect toxin prior to translocation (By similarity). Isolated HC binds to host synaptosomes and neurons, significantly decreases uptake and toxicity of whole BoNT/F (PubMed:19476346, PubMed:19650874). Interferes with uptake of BoNT/E and to a lesser extent BoNT/C (PubMed:19650874). in vitro binds gangliosides GT1b, GD1b and GD1a (PubMed:19650874, PubMed:19476346, PubMed:21849494). Binds to synaptic vesicle glycoproteins SV2A, SV2B and SV2C which may serve as coreceptors with gangliosides (PubMed:19650874, PubMed:19476346). Interaction with SV2 proteins requires SV2 glycosylation (PubMed:19476346). However knockout SV2A/SV2B mice still cleave synaptobrevin, leaving the identification of its receptor unclear (PubMed:21483489).[UniProtKB:P0DPI0][7] [8] [9] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBotulinum neurotoxin causes rapid flaccid paralysis through the inhibition of acetylcholine release at the neuromuscular junction. The seven BoNT serotypes (A-G) have been proposed to bind motor neurons via ganglioside-protein dual receptors. To date, the structure-function properties of BoNT/F host receptor interactions have not been resolved. Here, we report the crystal structures of the receptor binding domains (HCR) of BoNT/A and BoNT/F and the characterization of the dual receptors for BoNT/F. The overall polypeptide fold of HCR/A is essentially identical to the receptor binding domain of the BoNT/A holotoxin, and the structure of HCR/F is very similar to that of HCR/A, except for two regions implicated in neuronal binding. Solid phase array analysis identified two HCR/F binding glycans: ganglioside GD1a and oligosaccharides containing an N-acetyllactosamine core. Using affinity chromatography, HCR/F bound native synaptic vesicle glycoproteins as part of a protein complex. Deglycosylation of glycoproteins using alpha(1-3,4)-fucosidase, endo-beta-galactosidase, and PNGase F disrupted the interaction with HCR/F, while the binding of HCR/B to its cognate receptor, synaptotagmin I, was unaffected. These data indicate that the HCR/F binds synaptic vesicle glycoproteins through the keratan sulfate moiety of SV2. The interaction of HCR/F with gangliosides was also investigated. HCR/F bound specifically to gangliosides that contain alpha2,3-linked sialic acid on the terminal galactose of a neutral saccharide core (binding order GT1b = GD1a >> GM3; no binding to GD1b and GM1a). Mutations within the putative ganglioside binding pocket of HCR/F decreased binding to gangliosides, synaptic vesicle protein complexes, and primary rat hippocampal neurons. Thus, BoNT/F neuronal discrimination involves the recognition of ganglioside and protein (glycosylated SV2) carbohydrate moieties, providing a structural basis for the high affinity and specificity of BoNT/F for neurons. Glycosylated SV2 and Gangliosides as Dual Receptors for Botulinum Neurotoxin Serotype F.,Fu Z, Chen C, Barbieri JT, Kim JJ, Baldwin MR Biochemistry. 2009 Jun 23;48(24):5631-41. PMID:19476346[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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