scholarly journals A role for the syntaxin N-terminus

2009 ◽  
Vol 418 (1) ◽  
pp. e1-e3 ◽  
Author(s):  
Mary Munson ◽  
Nia J. Bryant
Keyword(s):  
Membrane Trafficking ◽  
Binding Mode ◽  
Detectable Effect ◽  
Binding Modes ◽  
Binding Interaction ◽  
Sm Proteins ◽  
Protein Receptor ◽  
Biochemical Journal ◽  
Sm Protein

Intracellular membrane fusion steps in eukaryotes require the syntaxin family of SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins. Syntaxins are regulated at several levels through interactions with regulatory proteins, including the SM (Sec1p/Munc18) proteins. Key to understanding this regulation is the characterization of different SM–syntaxin binding interactions at the molecular level and in terms of their contribution to function in vivo. The most conserved SM–syntaxin binding mode is through interaction of the syntaxin's extreme N-terminal peptide with a hydrophobic pocket on the surface of the SM protein. Surprisingly, mutant versions of two different SM proteins abrogated for this binding display no discernable phenotypes in vivo. In this issue of the Biochemical Journal, Johnson et al. demonstrate that loss of the N-terminal binding interaction between the syntaxin UNC-64 and the SM protein UNC-18 severely impairs neuromuscular synaptic transmission in Caenorhabditis elegans, resulting in an unco-ordinated phenotype. In contrast, loss of a second mode of SM–syntaxin binding has no detectable effect. Collectively, these results suggest that, although different membrane trafficking steps are all regulated by SM–syntaxin interactions using similar binding modes, they are differentially regulated, highlighting the need for careful dissection of the binding modes.

scholarly journals Characterization of two distinct binding modes between syntaxin 4 and Munc18c

2009 ◽  
Vol 419 (3) ◽  
pp. 655-660 ◽  
Author(s):  
Veronica Aran ◽  
Fiona M. Brandie ◽  
Alasdair R. Boyd ◽  
Theodoros Kantidakis ◽  
Elizabeth J. Rideout ◽  
...  
Keyword(s):  
Protein Function ◽  
Binding Mode ◽  
Binding Modes ◽  
Sm Proteins ◽  
Apparent Lack ◽  
Protein Receptor ◽  
Syntaxin 4 ◽  
Vacuolar Protein ◽  
Sm Protein

Interaction of SM (Sec1/Munc18) proteins with their cognate syntaxins represents an important regulatory mechanism of SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor)-mediated membrane fusion. Understanding the conserved mechanisms by which SM proteins function in this process has proved challenging, largely due to an apparent lack of conservation of binding mechanisms between different SM–syntaxin pairs. In the present study, we have identified a hitherto uncharacterized mode of binding between syntaxin 4 and Munc18c that is independent of the binding mode shown previously to utilize the N-terminal peptide of syntaxin 4. Our data demonstrate that syntaxin 4 and Munc18c interact via two distinct modes of binding, analogous to those employed by syntaxin 1a–Munc18a and syntaxin 16–Vps45p (vacuolar protein sorting 45). These data support the notion that all syntaxin/SM proteins bind using conserved mechanisms, and pave the way for the formulation of unifying hypotheses of SM protein function.

scholarly journals Spanning the gap: unraveling RSC dynamics in vivo

2021 ◽  
Author(s):  
Heinz Neumann ◽  
Bryan J. Wilkins
Keyword(s):  
Cell Cycle ◽  
Posttranslational Modifications ◽  
Transcriptional Activation ◽  
Binding Mode ◽  
Binding Modes ◽  
Binding Domains ◽  
Binding Interface ◽  
The Many ◽  
And Function

AbstractMultiple reports over the past 2 years have provided the first complete structural analyses for the essential yeast chromatin remodeler, RSC, providing elaborate molecular details for its engagement with the nucleosome. However, there still remain gaps in resolution, particularly within the many RSC subunits that harbor histone binding domains.Solving contacts at these interfaces is crucial because they are regulated by posttranslational modifications that control remodeler binding modes and function. Modifications are dynamic in nature often corresponding to transcriptional activation states and cell cycle stage, highlighting not only a need for enriched spatial resolution but also temporal understanding of remodeler engagement with the nucleosome. Our recent work sheds light on some of those gaps by exploring the binding interface between the RSC catalytic motor protein, Sth1, and the nucleosome, in the living nucleus. Using genetically encoded photo-activatable amino acids incorporated into histones of living yeast we are able to monitor the nucleosomal binding of RSC, emphasizing the regulatory roles of histone modifications in a spatiotemporal manner. We observe that RSC prefers to bind H2B SUMOylated nucleosomes in vivo and interacts with neighboring nucleosomes via H3K14ac. Additionally, we establish that RSC is constitutively bound to the nucleosome and is not ejected during mitotic chromatin compaction but alters its binding mode as it progresses through the cell cycle. Our data offer a renewed perspective on RSC mechanics under true physiological conditions.

scholarly journals The Sec1p/Munc18 protein Vps45p binds its cognate SNARE proteins via two distinct modes

2006 ◽  
Vol 173 (6) ◽  
pp. 927-936 ◽  
Author(s):  
Lindsay N. Carpp ◽  
Leonora F. Ciufo ◽  
Scott G. Shanks ◽  
Alan Boyd ◽  
Nia J. Bryant
Keyword(s):  
Crystal Structure ◽  
Membrane Trafficking ◽  
Protein Family ◽  
Snare Proteins ◽  
Outer Face ◽  
Sm Proteins ◽  
Hydrophobic Pocket ◽  
Second Mode ◽  
Sm Protein ◽  
Domain I

Sec1p/Munc18 (SM) proteins are essential for SNARE-mediated membrane trafficking. The formulation of unifying hypotheses for the function of the SM protein family has been hampered by the observation that two of its members bind their cognate syntaxins (Sxs) in strikingly different ways. The SM protein Vps45p binds its Sx Tlg2p in a manner analogous to that captured by the Sly1p–Sed5p crystal structure, whereby the NH2-terminal peptide of the Sx inserts into a hydrophobic pocket on the outer face of domain I of the SM protein. In this study, we report that although this mode of interaction is critical for the binding of Vps45p to Tlg2p, the SM protein also binds Tlg2p-containing SNARE complexes via a second mode that involves neither the NH2 terminus of Tlg2p nor the region of Vps45p that facilitates this interaction. Our findings point to the possibility that SM proteins interact with their cognate SNARE proteins through distinct mechanisms at different stages in the SNARE assembly/disassembly cycle.

Binding of UNC-18 to the N-terminus of syntaxin is essential for neurotransmission in Caenorhabditis elegans

2009 ◽  
Vol 418 (1) ◽  
pp. 73-80 ◽  
Author(s):  
James R. Johnson ◽  
Pawel Ferdek ◽  
Lu-Yun Lian ◽  
Jeff W. Barclay ◽  
Robert D. Burgoyne ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Membrane Fusion ◽  
Snare Complex ◽  
Binding Modes ◽  
Sm Proteins ◽  
Closed Conformation ◽  
Physiological Relevance ◽  
N Terminus

SNAREs (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptors) are widely accepted to drive all intracellular membrane fusion events. SM (Sec1/Munc18-like) proteins bind to SNAREs and this interaction may underlie their ubiquitous requirement for efficient membrane fusion. SM proteins bind to SNAREs in at least three modes: (i) to a closed conformation of syntaxin; (ii) to the syntaxin N-terminus; and (iii) to the assembled SNARE complex. Munc18-1 exhibits all three binding modes and recent in vitro reconstitution assays suggest that its interaction with the syntaxin N-terminus is essential for neuronal SNARE complex binding and efficient membrane fusion. To investigate the physiological relevance of these binding modes, we studied the UNC-18/UNC-64 SM/SNARE pair, which is essential for neuronal exocytosis in Caenorhabditis elegans. Mutations in the N-terminus of UNC-64 strongly inhibited binding to UNC-18, as did mutations targeting closed conformation binding. Complementary mutations in UNC-18 designed to selectively impair binding to either closed syntaxin or its N-terminus produced a similarly strong inhibition of UNC-64 binding. Therefore high-affinity UNC18/UNC-64 interaction in vitro involves both binding modes. To determine the physiological relevance of each mode, unc-18-null mutant worms were transformed with wild-type or mutant unc-18 constructs. The UNC-18(R39C) construct, that is defective in closed syntaxin binding, fully rescued the locomotion defects of the unc-18 mutant. In contrast, the UNC-18(F113R) construct, that is defective in binding to the N-terminus of UNC-64, provided no rescue. These results suggest that binding of UNC-18 to closed syntaxin is dispensable for membrane fusion, whereas interaction with the syntaxin N-terminus is essential for neuronal exocytosis in vivo.

scholarly journals Structure-based Functional Analysis Reveals a Role for the SM Protein Sly1p in Retrograde Transport to the Endoplasmic Reticulum

2005 ◽  
Vol 16 (9) ◽  
pp. 3951-3962 ◽  
Author(s):  
Yujie Li ◽  
Dieter Gallwitz ◽  
Renwang Peng
Keyword(s):  
Endoplasmic Reticulum ◽  
Mutational Analysis ◽  
Retrograde Transport ◽  
Snare Complex ◽  
Single Amino Acid ◽  
Temperature Sensitive ◽  
Sm Proteins ◽  
Sm Protein

Sec1p/Munc18 (SM) proteins are essential for membrane fusion events in eukaryotic cells. Here we describe a systematic, structure-based mutational analysis of the yeast SM protein Sly1p, which was previously shown to function in anterograde endoplasmic reticulum (ER)-to-Golgi and intra-Golgi protein transport. Five new temperature-sensitive (ts) mutants, each carrying a single amino acid substitution in Sly1p, were identified. Unexpectedly, not all of the ts mutants exhibited striking anterograde ER-to-Golgi transport defects. For example, in cells of the novel sly1-5 mutant, transport of newly synthesized lysosomal and secreted proteins was still efficient, but the ER-resident Kar2p/BiP was missorted to the outside of the cell, and two proteins, Sed5p and Rer1p, which normally shuttle between the Golgi and the ER, failed to relocate to the ER. We also discovered that in vivo, Sly1p was associated with a SNARE complex formed on the ER, and that in vitro, the SM protein directly interacted with the ER-localized nonsyntaxin SNAREs Use1p/Slt1p and Sec20p. Furthermore, several conditional mutants defective in Golgi-to-ER transport were synthetically lethal with sly1-5. Together, these results indicate a previously unrecognized function of Sly1p in retrograde transport to the endoplasmic reticulum.

scholarly journals SM protein Munc18-2 facilitates transition of Syntaxin 11-mediated lipid mixing to complete fusion for T-lymphocyte cytotoxicity

2017 ◽  
Vol 114 (11) ◽  
pp. E2176-E2185 ◽  
Author(s):  
Waldo A. Spessott ◽  
Maria L. Sanmillan ◽  
Margaret E. McCormick ◽  
Vineet V. Kulkarni ◽  
Claudio G. Giraudo
Keyword(s):  
Transmembrane Domain ◽  
Snare Complex ◽  
Complete Fusion ◽  
Sm Proteins ◽  
Granule Exocytosis ◽  
Cytolytic Granule ◽  
Syntaxin 11 ◽  
Sm Protein ◽  
Lytic Granule

The atypical lipid-anchored Syntaxin 11 (STX11) and its binding partner, the Sec/Munc (SM) protein Munc18-2, facilitate cytolytic granule release by cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Patients carrying mutations in these genes develop familial hemophagocytic lymphohistiocytosis, a primary immunodeficiency characterized by impaired lytic granule exocytosis. However, whether a SNARE such as STX11, which lacks a transmembrane domain, can support membrane fusion in vivo is uncertain, as is the precise role of Munc18-2 during lytic granule exocytosis. Here, using a reconstituted “flipped” cell–cell fusion assay, we show that lipid-anchored STX11 and its cognate SNARE proteins mainly support exchange of lipids but not cytoplasmic content between cells, resembling hemifusion. Strikingly, complete fusion is stimulated by addition of wild-type Munc18-2 to the assay, but not of Munc18-2 mutants with abnormal STX11 binding. Our data reveal that Munc18-2 is not just a chaperone of STX11 but also directly contributes to complete membrane merging by promoting SNARE complex assembly. These results further support the concept that SM proteins in general are part of the core fusion machinery. This fusion mechanism likely contributes to other cell-type–specific exocytic processes such as platelet secretion.

scholarly journals Mso1p Regulates Membrane Fusion through Interactions with the Putative N-Peptide–binding Area in Sec1p Domain 1

2010 ◽  
Vol 21 (8) ◽  
pp. 1362-1374 ◽  
Author(s):  
Marion Weber ◽  
Konstantin Chernov ◽  
Hilkka Turakainen ◽  
Gerd Wohlfahrt ◽  
Maria Pajunen ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Protein Interactions ◽  
Peptide Binding ◽  
Complex Function ◽  
Snare Complex ◽  
Targeted Mutagenesis ◽  
Rab Gtpase ◽  
Binding Modes ◽  
Sm Proteins ◽  
Sm Protein

Sec1p/Munc18 (SM) family proteins regulate SNARE complex function in membrane fusion through their interactions with syntaxins. In addition to syntaxins, only a few SM protein interacting proteins are known and typically, their binding modes with SM proteins are poorly characterized. We previously identified Mso1p as a Sec1p-binding protein and showed that it is involved in membrane fusion regulation. Here we demonstrate that Mso1p and Sec1p interact at sites of exocytosis and that the Mso1p–Sec1p interaction site depends on a functional Rab GTPase Sec4p and its GEF Sec2p. Random and targeted mutagenesis of Sec1p, followed by analysis of protein interactions, indicates that Mso1p interacts with Sec1p domain 1 and that this interaction is important for membrane fusion. In many SM family proteins, domain 1 binds to a N-terminal peptide of a syntaxin family protein. The Sec1p-interacting syntaxins Sso1p and Sso2p lack the N-terminal peptide. We show that the putative N-peptide binding area in Sec1p domain 1 is important for Mso1p binding, and that Mso1p can interact with Sso1p and Sso2p. Our results suggest that Mso1p mimics N-peptide binding to facilitate membrane fusion.

scholarly journals SNARE zippering requires activation by SNARE-like peptides in Sec1/Munc18 proteins

2018 ◽  
Vol 115 (36) ◽  
pp. E8421-E8429 ◽  
Author(s):  
Haijia Yu ◽  
Chong Shen ◽  
Yinghui Liu ◽  
Bridget L. Menasche ◽  
Yan Ouyang ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Lipid Bilayers ◽  
Fusion Reaction ◽  
Coiled Coil ◽  
Fusion Reactions ◽  
Sm Proteins ◽  
Close Proximity ◽  
Protein Receptors ◽  
Sm Protein

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) catalyze membrane fusion by forming coiled-coil bundles between membrane bilayers. The SNARE bundle zippers progressively toward the membranes, pulling the lipid bilayers into close proximity to fuse. In this work, we found that the +1 and +2 layers in the C-terminal domains (CTDs) of SNAREs are dispensable for reconstituted SNARE-mediated fusion reactions. By contrast, all CTD layers are required for fusion reactions activated by the cognate Sec1/Munc18 (SM) protein or a synthetic Vc peptide derived from the vesicular (v-) SNARE, correlating with strong acceleration of fusion kinetics. These results suggest a similar mechanism underlying the stimulatory functions of SM proteins and Vc peptide in SNARE-dependent membrane fusion. Unexpectedly, we identified a conserved SNARE-like peptide (SLP) in SM proteins that structurally and functionally resembles Vc peptide. Like Vc peptide, SLP binds and activates target (t-) SNAREs, accelerating the fusion reaction. Disruption of the t-SNARE–SLP interaction inhibits exocytosis in vivo. Our findings demonstrated that a t-SNARE–SLP intermediate must form before SNAREs can drive efficient vesicle fusion.

Role of Munc18-1 in synaptic vesicle and large dense-core vesicle secretion

2003 ◽  
Vol 31 (4) ◽  
pp. 848-850 ◽  
Author(s):  
R.F.G. Toonen
Keyword(s):  
Membrane Trafficking ◽  
Function Analysis ◽  
Dense Core Vesicle ◽  
Fusion Reactions ◽  
Sm Proteins ◽  
Positive Role ◽  
Protein Levels ◽  
Sm Protein ◽  
Vesicle Secretion

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex formation between a vesicle and the target membrane is a central aspect of probably all vesicle fusion reactions. The sec1/munc18 (SM) protein family is also involved in membrane trafficking and fusion events. However, in contrast with the consensus on SNARE protein function, analysis of SM proteins in different systems has produced different ideas about their exact role, their site of action and their relationship to SNARE proteins. Deletion of the SM protein involved in secretory vesicle release in mice, Munc18-1, results in a complete block of exocytosis. Manipulation of Munc18-1 protein levels in neurons and adrenal chromaffin cells argues for a positive role of this protein in vesicle secretion, as overexpression results in an increase in vesicle secretion. A decrease in Munc18-1 protein levels, on the other hand, leads to a decrease in vesicle secretion.

scholarly journals Binding Mode Exploration of B1 Receptor Antagonists’ by the Use of Molecular Dynamics and Docking Simulation—How Different Target Engagement Can Determine Different Biological Effects

2020 ◽  
Vol 21 (20) ◽  
pp. 7677
Author(s):  
Marica Gemei ◽  
Carmine Talarico ◽  
Laura Brandolini ◽  
Candida Manelfi ◽  
Lorena Za ◽  
...  
Keyword(s):  
Biological Effects ◽  
Critical Role ◽  
Binding Mode ◽  
Receptor Internalization ◽  
Mode Analysis ◽  
Binding Modes ◽  
Pharmacological Characterization ◽  
B1 Receptor

The kinin B1 receptor plays a critical role in the chronic phase of pain and inflammation. The development of B1 antagonists peaked in recent years but almost all promising molecules failed in clinical trials. Little is known about these molecules’ mechanisms of action and additional information will be necessary to exploit the potential of the B1 receptor. With the aim of contributing to the available knowledge of the pharmacology of B1 receptors, we designed and characterized a novel class of allosteric non-peptidic inhibitors with peculiar binding characteristics. Here, we report the binding mode analysis and pharmacological characterization of a new allosteric B1 antagonist, DFL20656. We analyzed the binding of DFL20656 by single point mutagenesis and radioligand binding assays and we further characterized its pharmacology in terms of IC50, B1 receptor internalization and in vivo activity in comparison with different known B1 antagonists. We highlighted how different binding modes of DFL20656 and a Merck compound (compound 14) within the same molecular pocket can affect the biological and pharmacological properties of B1 inhibitors. DFL20656, by its peculiar binding mode, involving tight interactions with N114, efficiently induced B1 receptor internalization and evoked a long-lasting effect in an in vivo model of neuropathic pain. The pharmacological characterization of different B1 antagonists highlighted the effects of their binding modes on activity, receptor occupancy and internalization. Our results suggest that part of the failure of most B1 inhibitors could be ascribed to a lack of knowledge about target function and engagement.

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