{"id":{"repo_id":"utswmed","oai_identifier":"oai:utswmed-ir.tdl.org:2152.5/893"},"canonical_url":"https://search.dev.ndltd.org/etd/utswmed/oai:utswmed-ir.tdl.org:2152.5/893","repository":{"repo_id":"utswmed","name":"University of Texas Southwestern Medical Center","base_url":"https://utswmed-ir.tdl.org/server/oai/request"},"display":{"title":"Structural and Functional Studies of Munc18 and SNARE Proteins","abstract":"Release of neurotransmitters is a tightly regulated process and a key event in interneuron communication. Release involves a series of steps, including vesicles docking to the active zone of the plasma membrane, priming to a readily releasable state, and Ca2+-triggered membrane fusion. These steps are tightly controlled by an intricate protein machinery. Essential components of this machinery are proteins from the Sec1/Munc18 (SM) and SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptors) families. SNAREs function by forming a four-helix bundle called SNARE complex; assembly of the SNARE complex brings two membranes together and is key for membrane fusion. The function of SM proteins is less clear. The neuronal SM proteins Munc18-1 was identified and linked to synaptic vesicle fusion due to its tight binding to syntaxin-1. The strict requirement of Munc18-1 for release is illustrated by the observation that, in mice, deletion of Munc18-1 abolished neurotransmitter release completely. Munc18-1 binds to the closed conformation of syntaxin-1 as well as to assembled SNARE complexes containing open syntaxin-1. Analysis of point mutations on Munc18-1 showed that binding of Munc18-1 to the Habc domain of open syntaxin-1 is critical for synaptic vesicle priming but not for the release step. The fact that Munc18-1 and complexin-1 could bind simultaneously to the SNARE complex suggested Munc18-1 remained bound to a macrocomplex that is poised for Ca2+ triggering of fusion. Analysis using diverse biophysical approaches revealed that Munc18-1 indeed binds to the C-terminus of the synaptobrevin SNARE motif and to the SNARE four-helix bundle. Both interactions have similar affinities and the N-terminal region of syntaxin-1 competes with the SNARE four-helix bundle and synaptobrevin for Munc18-1 binding, suggesting that the interaction between Munc18-1 and the SNARE four-helix bundle involves the same cavity of Munc18-1 that binds to syntaxin-1. To directly test Munc18-1’s role in fusion, I reconstituted v- and t-SNAREs into separate liposomes. Fusion between these proteoliposomes in the presence of Munc18-1 was monitored with a lipid mixing assay. Intriguingly, I found that enhanced lipid mixing caused by rat Munc18-1 alone was observed. Biochemistry studies showed that denaturation of rat Munc18-1 or squid Munc18-1 causes membrane lipid mixing in the absence of SNAREs proteins.","abstract_html":"Release of neurotransmitters is a tightly regulated process and a key event in interneuron communication. Release involves a series of steps, including vesicles docking to the active zone of the plasma membrane, priming to a readily releasable state, and Ca2+-triggered membrane fusion. These steps are tightly controlled by an intricate protein machinery. Essential components of this machinery are proteins from the Sec1/Munc18 (SM) and SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptors) families. SNAREs function by forming a four-helix bundle called SNARE complex; assembly of the SNARE complex brings two membranes together and is key for membrane fusion. The function of SM proteins is less clear. The neuronal SM proteins Munc18-1 was identified and linked to synaptic vesicle fusion due to its tight binding to syntaxin-1. The strict requirement of Munc18-1 for release is illustrated by the observation that, in mice, deletion of Munc18-1 abolished neurotransmitter release completely. Munc18-1 binds to the closed conformation of syntaxin-1 as well as to assembled SNARE complexes containing open syntaxin-1. Analysis of point mutations on Munc18-1 showed that binding of Munc18-1 to the Habc domain of open syntaxin-1 is critical for synaptic vesicle priming but not for the release step. The fact that Munc18-1 and complexin-1 could bind simultaneously to the SNARE complex suggested Munc18-1 remained bound to a macrocomplex that is poised for Ca2+ triggering of fusion. Analysis using diverse biophysical approaches revealed that Munc18-1 indeed binds to the C-terminus of the synaptobrevin SNARE motif and to the SNARE four-helix bundle. Both interactions have similar affinities and the N-terminal region of syntaxin-1 competes with the SNARE four-helix bundle and synaptobrevin for Munc18-1 binding, suggesting that the interaction between Munc18-1 and the SNARE four-helix bundle involves the same cavity of Munc18-1 that binds to syntaxin-1. To directly test Munc18-1’s role in fusion, I reconstituted v- and t-SNAREs into separate liposomes. Fusion between these proteoliposomes in the presence of Munc18-1 was monitored with a lipid mixing assay. Intriguingly, I found that enhanced lipid mixing caused by rat Munc18-1 alone was observed. Biochemistry studies showed that denaturation of rat Munc18-1 or squid Munc18-1 causes membrane lipid mixing in the absence of SNAREs proteins.","abstract_has_math":false,"creators":["Xu, Yi"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Rizo-Rey, José"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-08-26T17:35:42Z","date_published":"2011-08-26T17:35:42Z","updated_at":"2026-07-24T05:52:38Z","subjects":["SNARE Proteins","Munc18 Proteins","Nerve Tissue Proteins"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["759117590"],"render_values":[{"text":"759117590","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/2152.5/893","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Rizo-Rey, José"]},{"key":"dc:creator","label":"Author","values":["Xu, Yi"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-08-26T17:35:42Z","2011-08-10"]},{"key":"dc:type","label":"Dc Type","values":["Thesis","Text"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["SNARE Proteins","Munc18 Proteins","Nerve Tissue Proteins"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2152.5/893","759117590"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Release of neurotransmitters is a tightly regulated process and a key event in interneuron communication. Release involves a series of steps, including vesicles docking to the active zone of the plasma membrane, priming to a readily releasable state, and Ca2+-triggered membrane fusion. These steps are tightly controlled by an intricate protein machinery. Essential components of this machinery are proteins from the Sec1/Munc18 (SM) and SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptors) families. SNAREs function by forming a four-helix bundle called SNARE complex; assembly of the SNARE complex brings two membranes together and is key for membrane fusion. The function of SM proteins is less clear. The neuronal SM proteins Munc18-1 was identified and linked to synaptic vesicle fusion due to its tight binding to syntaxin-1. The strict requirement of Munc18-1 for release is illustrated by the observation that, in mice, deletion of Munc18-1 abolished neurotransmitter release completely. Munc18-1 binds to the closed conformation of syntaxin-1 as well as to assembled SNARE complexes containing open syntaxin-1. Analysis of point mutations on Munc18-1 showed that binding of Munc18-1 to the Habc domain of open syntaxin-1 is critical for synaptic vesicle priming but not for the release step. The fact that Munc18-1 and complexin-1 could bind simultaneously to the SNARE complex suggested Munc18-1 remained bound to a macrocomplex that is poised for Ca2+ triggering of fusion. Analysis using diverse biophysical approaches revealed that Munc18-1 indeed binds to the C-terminus of the synaptobrevin SNARE motif and to the SNARE four-helix bundle. Both interactions have similar affinities and the N-terminal region of syntaxin-1 competes with the SNARE four-helix bundle and synaptobrevin for Munc18-1 binding, suggesting that the interaction between Munc18-1 and the SNARE four-helix bundle involves the same cavity of Munc18-1 that binds to syntaxin-1. To directly test Munc18-1’s role in fusion, I reconstituted v- and t-SNAREs into separate liposomes. Fusion between these proteoliposomes in the presence of Munc18-1 was monitored with a lipid mixing assay. Intriguingly, I found that enhanced lipid mixing caused by rat Munc18-1 alone was observed. Biochemistry studies showed that denaturation of rat Munc18-1 or squid Munc18-1 causes membrane lipid mixing in the absence of SNAREs proteins."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Structural and Functional Studies of Munc18 and SNARE Proteins"]}]}],"canonical_facts":{"dc:contributor":["Rizo-Rey, José"],"dc:creator":["Xu, Yi"],"dc:date":["2011-08-26T17:35:42Z","2011-08-10"],"dc:description":["Release of neurotransmitters is a tightly regulated process and a key event in interneuron communication. Release involves a series of steps, including vesicles docking to the active zone of the plasma membrane, priming to a readily releasable state, and Ca2+-triggered membrane fusion. These steps are tightly controlled by an intricate protein machinery. Essential components of this machinery are proteins from the Sec1/Munc18 (SM) and SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptors) families. SNAREs function by forming a four-helix bundle called SNARE complex; assembly of the SNARE complex brings two membranes together and is key for membrane fusion. The function of SM proteins is less clear. The neuronal SM proteins Munc18-1 was identified and linked to synaptic vesicle fusion due to its tight binding to syntaxin-1. The strict requirement of Munc18-1 for release is illustrated by the observation that, in mice, deletion of Munc18-1 abolished neurotransmitter release completely. Munc18-1 binds to the closed conformation of syntaxin-1 as well as to assembled SNARE complexes containing open syntaxin-1. Analysis of point mutations on Munc18-1 showed that binding of Munc18-1 to the Habc domain of open syntaxin-1 is critical for synaptic vesicle priming but not for the release step. The fact that Munc18-1 and complexin-1 could bind simultaneously to the SNARE complex suggested Munc18-1 remained bound to a macrocomplex that is poised for Ca2+ triggering of fusion. Analysis using diverse biophysical approaches revealed that Munc18-1 indeed binds to the C-terminus of the synaptobrevin SNARE motif and to the SNARE four-helix bundle. Both interactions have similar affinities and the N-terminal region of syntaxin-1 competes with the SNARE four-helix bundle and synaptobrevin for Munc18-1 binding, suggesting that the interaction between Munc18-1 and the SNARE four-helix bundle involves the same cavity of Munc18-1 that binds to syntaxin-1. To directly test Munc18-1’s role in fusion, I reconstituted v- and t-SNAREs into separate liposomes. Fusion between these proteoliposomes in the presence of Munc18-1 was monitored with a lipid mixing assay. Intriguingly, I found that enhanced lipid mixing caused by rat Munc18-1 alone was observed. Biochemistry studies showed that denaturation of rat Munc18-1 or squid Munc18-1 causes membrane lipid mixing in the absence of SNAREs proteins."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2152.5/893","759117590"],"dc:language":["en"],"dc:subject":["SNARE Proteins","Munc18 Proteins","Nerve Tissue Proteins"],"dc:title":["Structural and Functional Studies of Munc18 and SNARE Proteins"],"dc:type":["Thesis","Text"]},"updated_at":"2026-07-24T05:52:38Z"}