Actin remodeling in regulated exocytosis: toward a mesoscopic view

Cellular communication relies on fusion of secretory vesicles with the plasma membrane, following dynamic events that change the micro- and nanoscale environment of the approaching vesicles in the vicinity of docking sites. Visualization of fine cortical actin network structures and their interactions with vesicle and plasma membrane has recently been facilitated by the development of new imaging technologies. Consequently, a greater understanding is emerging of the role of the cortical actin network on controlling secretory vesicles as they undergo docking, priming, and fusion in exocytic hot spots. In this review, we propose a mechanistic framework underpinning the mesoscopic properties of the cortical actin and discuss how molecular coupling of these pleiotropic effects orchestrate every single step of regulated exocytosis

Need for speed: Super-resolving the dynamic nanoclustering of syntaxin-1 at exocytic fusion sites

Communication between cells relies on regulated exocytosis, a multi-step process that involves the docking, priming and fusion of vesicles with the plasma membrane, culminating in the release of neurotransmitters and hormones. Key proteins and lipids involved in exocytosis are subjected to Brownian movement and constantly switch between distinct motion states which are governed by short-lived molecular interactions. Critical biochemical reactions between exocytic proteins that occur in the confinement of nanodomains underpin the precise sequence of priming steps which leads to the fusion of vesicles. The advent of super-resolution microscopy techniques has provided the means to visualize individual molecules on the plasma membrane with high spatiotemporal resolution in live cells. These techniques are revealing a highly dynamic nature of the nanoscale organization of the exocytic machinery. In this review, we focus on soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) syntaxin-1, which mediates vesicular fusion. Syntaxin-1 is highly mobile at the plasma membrane, and its inherent speed allows fast assembly and disassembly of syntaxin-1 nanoclusters which are associated with exocytosis. We reflect on recent studies which have revealed the mechanisms regulating syntaxin-1 nanoclustering on the plasma membrane and draw inferences on the effect of synaptic activity, phosphoinositides, N-ethylmaleimide-sensitive factor (NSF), α-soluble NSF attachment protein (α-SNAP) and SNARE complex assembly on the dynamic nanoscale organization of syntaxin-1

Actin Remodeling in Regulated Exocytosis: Toward a Mesoscopic View.

Cellular communication relies on fusion of secretory vesicles with the plasma membrane, following dynamic events that change the micro- and nanoscale environment of the approaching vesicles in the vicinity of docking sites. Visualization of fine cortical actin network structures and their interactions with vesicle and plasma membrane has recently been facilitated by the development of new imaging technologies. Consequently, a greater understanding is emerging of the role of the cortical actin network on controlling secretory vesicles as they undergo docking, priming, and fusion in exocytic hot spots. In this review, we propose a mechanistic framework underpinning the mesoscopic properties of the cortical actin and discuss how molecular coupling of these pleiotropic effects orchestrate every single step of regulated exocytosis.status: publishe

A role for SNAREs in neuronal survival?

Read the full article Botulinum protease-cleaved snare fragments induce cytotoxicity in neuroblastoma cells' on page

Need for speed: Super-resolving the dynamic nanoclustering of syntaxin-1 at exocytic fusion sites

Communication between cells relies on regulated exocytosis, a multi-step process that involves the docking, priming and fusion of vesicles with the plasma membrane, culminating in the release of neurotransmitters and hormones. Key proteins and lipids involved in exocytosis are subjected to Brownian movement and constantly switch between distinct motion states which are governed by short-lived molecular interactions. Critical biochemical reactions between exocytic proteins that occur in the confinement of nanodomains underpin the precise sequence of priming steps which leads to the fusion of vesicles. The advent of super-resolution microscopy techniques has provided the means to visualize individual molecules on the plasma membrane with high spatiotemporal resolution in live cells. These techniques are revealing a highly dynamic nature of the nanoscale organization of the exocytic machinery. In this review, we focus on soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) syntaxin-1, which mediates vesicular fusion. Syntaxin-1 is highly mobile at the plasma membrane, and its inherent speed allows fast assembly and disassembly of syntaxin-1 nanoclusters which are associated with exocytosis. We reflect on recent studies which have revealed the mechanisms regulating syntaxin-1 nanoclustering on the plasma membrane and draw inferences on the effect of synaptic activity, phosphoinositides, N-ethylmaleimide-sensitive factor (NSF), α-soluble NSF attachment protein (α-SNAP) and SNARE complex assembly on the dynamic nanoscale organization of syntaxin-1. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.status: publishe

0730 Association Between Fruit Drink Intake and Healthy Sleep: An Examination of National Health Interview Survey data

Abstract Introduction Sugar-sweetened beverage (SSB) intake is associated with obesity, diabetes and metabolic syndrome risk. Harvard School of Public Health Beverage Guidelines ideally recommends zero intake of SSBs. SSBs include fruit drinks containing added sugar, and are often high calories, and low in nutritional value. Regular fruit drink intake may be an indicator of poor overall diet quality, which has been associated with sleep health. In this study, we assessed associations of fruit drink intake with healthy sleep. Methods Data from the present analysis came from the National Health Interview Survey [2000–2016] (N=57,252). The survey applies a stratified multistage sample survey of the resident civilian non-institutionalized US population. Respondents provided sociodemographic and physician-diagnosed chronic conditions. Self-reported sleep data was used to classify respondents based on sleep duration; insufficient sleepers were coded as (8hours /night, referenced to healthy sleepers (7–8 hours/night). Fruit drink frequency intake was classified as healthy (never or once monthly) compared to unhealthy fruit drink intake (daily or weekly). SPSS v 23 was used to conduct regression analysis to test our hypothesis. Results The average age of the sample was 39.96 ± 2.47 years. Of the sample 48.3% were male and 51.7% were female. The race composition was as follows: 76.6% white and 23.4% comprised all other minority groups. Results of the adjusted logistic regression analysis showed that insufficient sleepers had a 5% greater likelihood of consuming fruit drinks (OR = 1.05, 95% CI 1.01–1.10, p<.05). Long sleepers were 30% more likely to consume fruit drinks (OR = 1.30 95% CI 1.20–1.40, p<0.001). Analysis adjusted for age, sex, race/ethnicity, and BMI. Conclusion Long sleepers are more likely to be high fruit drink consumers. Fruit drink intake should be reduced as part of an overall diet regimen, which may also have implications for sleep health. Support (If Any) This research was supported by funding from the NIH (T32HL129953, RO1MD007716 and K07AG052685) and Dr. Williams was supported by NIH/NHLBI grant number K23HL125939

In vivo single-molecule tracking at the Drosophila presynaptic motor nerve terminal

An increasing number of super-resolution microscopy techniques are helping to uncover the mechanisms that govern the nanoscale cellular world. Single-molecule imaging is gaining momentum as it provides exceptional access to the visualization of individual molecules in living cells. Here, we describe a technique that we developed to perform single-particle tracking photo-activated localization microscopy (sptPALM) in Drosophila larvae. Synaptic communication relies on key presynaptic proteins that act by docking, priming, and promoting the fusion of neurotransmitter-containing vesicles with the plasma membrane. A range of protein-protein and protein-lipid interactions tightly regulates these processes and the presynaptic proteins therefore exhibit changes in mobility associated with each of these key events. Investigating how mobility of these proteins correlates with their physiological function in an intact live animal is essential to understanding their precise mechanism of action. Extracting protein mobility with high resolution in vivo requires overcoming limitations such as optical transparency, accessibility, and penetration depth. We describe how photoconvertible fluorescent proteins tagged to the presynaptic protein Syntaxin-1A can be visualized via slight oblique illumination and tracked at the motor nerve terminal or along the motor neuron axon of the third instar Drosophila larva