title: Synaptotagmins I and II mediate entry of botulinum neurotoxin B into cells.
abstract: Botulinum neurotoxins (BoNTs) cause botulism by entering neurons and cleaving proteins that mediate neurotransmitter release; disruption of exocytosis results in paralysis and death. The receptors for BoNTs are thought to be composed of both proteins and gangliosides; however, protein components that mediate toxin entry have not been identified. Using gain-of-function and loss-of-function approaches, we report here that the secretory vesicle proteins, synaptotagmins (syts) I and II, mediate the entry of BoNT/B (but not BoNT/A or E) into PC12 cells. Further, we demonstrate that BoNT/B entry into PC12 cells and rat diaphragm motor nerve terminals was activity dependent and can be blocked using fragments of syt II that contain the BoNT/B-binding domain. Finally, we show that syt II fragments, in conjunction with gangliosides, neutralized BoNT/B in intact mice. These findings establish that syts I and II can function as protein receptors for BoNT/B.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001905:Botulinum Toxins / Q000493:pharmacokinetics*; D019274:Botulinum Toxins, Type A; D001906:Botulism / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D005260:Female; D005732:Gangliosides / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D017434:Protein Structure, Tertiary; D051381:Rats; D050861:Synaptotagmin II; D050857:Synaptotagmins
chemical_list: D002135:Calcium-Binding Proteins; D005732:Gangliosides; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D050861:Synaptotagmin II; C494263:Syt2 protein, mouse; C494264:Syt2 protein, rat; C096323:rimabotulinumtoxinB; D050857:Synaptotagmins; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A