Measuring Ca2+-Induced Structural Changes in Lipid Monolayers: Implications for Synaptic Vesicle Exocytosis

Ghosh, Sajal K.; Castorph, Simon; Konovalov, Oleg; Salditt, Tim; Jahn, Reinhard; Holt, Matthew

doi:10.1016/j.bpj.2012.01.006

Cited by 19 publications

(16 citation statements)

References 38 publications

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“…Upon Ca 2+ injection we observed a fast fusion burst with a rise time faster than 100 msec 14,18 . In contrast, neuronal SNAREs alone produced only a lipid-mixing burst upon Ca 2+ -injection, but with little content mixing; the effect of Ca 2+ in this SNARE-only case is likely caused by PIP 2 in the acceptor vesicle membranes 33 . This example illustrates the importance of monitoring content mixing since lipid mixing can occur well before, or without, content mixing.…”

Section: Introductionmentioning

confidence: 75%

Studying calcium-triggered vesicle fusion in a single vesicle-vesicle content and lipid-mixing system

et al. 2012

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This Protocol describes a single vesicle-vesicle microscopy system to study Ca2+-triggered vesicle fusion. Donor vesicles contain reconstituted synaptobrevin and synaptotagmin-1. Acceptor vesicles contain reconstituted syntaxin and SNAP-25, and are tethered to a PEG-coated glass surface. Donor vesicles are mixed with the tethered acceptor vesicles and incubated for several minutes at zero Ca2+-concentration, resulting in a collection of single interacting vesicle pairs. The donor vesicles also contain two spectrally distinct fluorophores that allow simultaneous monitoring of temporal changes of the content and membrane. Upon Ca2+-injection into the sample chamber, our system therefore differentiates between hemifusion and complete fusion of interacting vesicle pairs and determines the temporal sequence of these events on a sub-hundred millisecond timescale. Other factors, such as complexin, can be easily added. Our system is unique by monitoring both content and lipid mixing, and by starting from a metastable state of interacting vesicle pairs prior to Ca2+-injection.

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Section: Introductionmentioning

confidence: 75%

Studying calcium-triggered vesicle fusion in a single vesicle-vesicle content and lipid-mixing system

et al. 2012

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“…To obtain further insight into these aspects of PGNP–SLB interactions, especially the extent of penetration of the PGNPs within the SLBs, let us turn our attention to the in situ XR and GID measurements performed on the DMPC SLB transferred at Π = 40 mN m −1 after they were incubated with Au‐PST3K and Au‐PST53K hydrophobic PGNPs (see methods) . Figure b shows XR (Fresnel normalized) data as a function of out of plane wave vector

q_{normalz} (= \frac{4 π}{λ_{x}} \sin α)

, collected on these SLBs before and after they were incubated with nanoparticles.…”

Section: Resultsmentioning

confidence: 99%

Plasmonic Lipid Bilayer Membranes for Enhanced Detection Sensitivity of Biolabeling Fluorophores

Bhattacharya

Indukuri

Begam

et al. 2015

Adv Funct Materials

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Plasmonics based sensing using the surface plasmon resonance of metal nanoparticles has been effectively demonstrated in various applications. Extending this methodology to cell and artificial lipid bilayer membranes would be extremely beneficial in enhancing the sensitivity of the detection of binding and cellular transport of molecules across such membranes. Here we demonstrate the creation of a artificial plasmonic biomembrane template and use it to demonstrate the enhanced detection sensitivity of certain widely used biomarker molecules. The efficacy of these templates are explained in terms of the ability of the hydrophobic polymer grafted gold nanoparticles, used, to organize, penetrate and fluidize the membranes. The enhancement of photoluminescence of the dye molecules used occurs over a reasonably large spectral range as compared to the plasmon resonance of gold nanoparticles. The results could, possibly, be extended to cellular membrane with relevant modifications, as well as to detection of any other biological molecules, appropriately labeled with fluorescent dye molecules and demonstrates the versatility of these plasmonic bio-inspired platforms as potential bio-chemical sensors.

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“…2C). The effect of Ca 2+ on PIP 2 -containing monolayers has also been investigated by X-ray reflectivity and grazing incidence X-ray diffraction (GIXD) (Ghosh et al, 2011; Ghosh et al, 2010; Ghosh et al, 2012) to determine the lateral structure of 5 mol% PIP 2 in a background of neutral PC (DOPC or DPPC) in a pH7.4 buffer with a physiological ionic strength. The X-ray studies reveal a homogeneous distribution of PIP 2 in DOPC multilamellar films since neither a second set of Bragg peaks from scattering nor splitting of the head-group electron density from its electron density profiles (EDPs) was evident at a relative humidity (RH) • 90% (Ghosh et al, 2011).…”

Section: Experimental Studies Of Cation-mediated Interactions Amonmentioning

confidence: 99%

“…Interestingly, two distinct lamellar phases, as indicated by two sets of Braggs peaks, are found for pure PIP2 from porcine brain throughout a wide range of relative humidity values in the same study. In a follow up study, the same group studies the condensing effect of Ca 2+ to PIP 2 -containing free-standing monolayers in a background of DPPC (Ghosh et al, 2012). As shown in Fig.…”

Section: Experimental Studies Of Cation-mediated Interactions Amonmentioning

confidence: 99%

Counterion-mediated cluster formation by polyphosphoinositides

Wang

Slochower

Janmey

2014

Chemistry and Physics of Lipids

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Polyphosphoinositides (PPI) and in particular PI(4,5)P2, are among the most highly charged molecules in cell membranes, are important in many cellular signaling pathways, and are frequently targeted by peripheral polybasic proteins for anchoring through electrostatic interactions. Such interactions between PIP2 and proteins containing polybasic stretches depend on the physical state and the lateral distribution of PIP2 within the inner leaflet of the cell's lipid bilayer. The physical chemical properties of PIP2 such as pH-dependent changes in headgroup ionization and area per molecule as determined by experiments together with molecular simulations that predict headgroup conformations at various ionization states have revealed the electrostatic properties and phase behavior of PIP2-containing membranes. This review focuses on recent experimental and computational developments in defining the physical chemistry of PIP2 and its interactions with counterions. Ca2+-induced changes in PIP2 charge, conformation, and lateral structure within the membrane are documented by numerous experimental and computational studies. A simplified electrostatic model successfully predicts the Ca2+-driven formation of PIP2 clusters but cannot account for the different effects of Ca2+ and Mg2+ on PIP2-containing membranes. A more recent computational study is able to see the difference between Ca2+ and Mg2+ binding to PIP2 in the absence of a membrane and without cluster formation. Spectroscopic studies suggest that divalent cation- and multivalent polyamine-induced changes in the PIP2 lateral distribution in model membrane are also different, and not simply related to the net charge of the counterion. Among these differences is the capacity of Ca2+ but not other polycations to induce nm scale clusters of PIP2 in fluid membranes. Recent super resolution optical studies show that PIP2 forms nanoclusters in the inner leaflet of a plasma membrane with a similar size distribution as those induced by Ca2+ in model membranes. The mechanisms by which PIP2 forms nanoclusters and other structures inside a cell remain to be determined, but the unique electrostatic properties of PIP2 and its interactions with multivalent counterions might have particular physiological relevance.

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Measuring Ca2+-Induced Structural Changes in Lipid Monolayers: Implications for Synaptic Vesicle Exocytosis

Cited by 19 publications

References 38 publications

Studying calcium-triggered vesicle fusion in a single vesicle-vesicle content and lipid-mixing system

Studying calcium-triggered vesicle fusion in a single vesicle-vesicle content and lipid-mixing system

Plasmonic Lipid Bilayer Membranes for Enhanced Detection Sensitivity of Biolabeling Fluorophores

Counterion-mediated cluster formation by polyphosphoinositides

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