The initial surface composition and topography modulate sphingomyelinase-driven sphingomyelin to ceramide conversion in lipid monolayers

Tullio, Luisina De; Maggio, Bruno; Härtel, Steffen; Jara, Jorge Jiménez de la; Fanani, María Laura

doi:10.1007/s12013-007-0001-1

Cited by 18 publications

(25 citation statements)

References 40 publications

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“…A detailed study of the time course of the SM degradation by SMase showed a correlation between the formation of Cer-enriched LC domains (immersed in a SM-enriched LE continuous phase) and the attainment of full catalytic capacity at the end of a lag period (18,19). Recently, we showed how the initial presence of Cer-enriched LC domains favors precatalytic steps of SMase activation in a way that is dependent on the amount of the lateral interface present (20). These results point out that, similar to PLA 2 , SMase action is also regulated by the presence of lateral membrane defects.…”

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confidence: 94%

Sphingomyelinase acts by an area-activated mechanism on the liquid-expanded phase of sphingomyelin monolayers

Tullio

Maggio

Fanani

2008

Journal of Lipid Research

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We describe the localization of Alexa-488-labeled SMase in SM/ceramide (Cer) lipid monolayers containing segregated liquid-condensed (LC) Cer-enriched domains surrounded by a continuous liquid-expanded (LE) SMenriched phase. Langmuir-Schaefer films were made in order to visualize the labeled enzyme. Independently of initial conditions Alexa-SMase is preferably localized in the SMenriched LE phase and it is not enriched at the domain boundaries. A novel mechanism is proposed for the action of SMase, which can also explain the regulatory effect of the surface topography on the enzyme activity. The homogeneous enzymatic generation of Cer in the LE phase leads to a meta-stable, kinetically trapped, supersaturated mixed monolayer. This effect acts as driving force for the segregation of the Cer-enriched domain following classical nucleation mechanisms. Accordingly, the number and size of Cer-enriched domains are determined by the extent of Cer supersaturation in the LE phase rather than by the SMase local activity. The kinetic barrier for nucleation, for which a compositional gap of at least 53 mol% of Cer is necessary to reach a thermodynamically stable LC phase, can explain the lag time to reaching full catalytic activity. Altogether, the data support an "area-activated mechanism," in which the enzyme is homogeneously active over the LE surface. Phospholipases are a group of mostly water-soluble enzymes, widely spread in nature, that perform their catalytic activity at an interface, owing to the insoluble nature of their substrates (1). Several studies have equated "membrane defects," such as those arising from the coexistence of lipid domains in different physical states, with enhanced catalytic activity (2-8). In 1990, it was reported that the liquidexpanded (LE), liquid-condensed (LC) lateral interfaces (lipid domain borders) in a one-component monolayer of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) act as starting points for Naja naja phospholipase A 2 (PLA 2 ) catalytic activity (9). Dahmen-Levison, Brezesinski, and Mohwald (10) showed in lipid monolayers that the fluorescent-labeled PLA 2 preferably accumulates at the LC-LE interface of domains. Those results support the socalled perimeter-activated or border-activated mechanism, in which the enzyme must have physical contact with the domain boundary/membrane defect in order to become fully active and exerts its major catalytic action adsorbed to these linear interfaces (11). However, more recent studies (12) have demonstrated that fluorescein-labeled PLA 2 from Crotalus atrox was homogeneously distributed in 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and DPPC giant unilamellar vesicles when the lipids were in the LE state and preferentially localized in the LE phase at temperatures corresponding to the gel-fluid phase coexistence. The homogeneous distribution of PLA 2 on the membrane surface would support a mechanism by which the enzyme is fully active over the whole fluid surface (area-activated mechanism) but cannot adequately explain...

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confidence: 94%

Sphingomyelinase acts by an area-activated mechanism on the liquid-expanded phase of sphingomyelin monolayers

Tullio

Maggio

Fanani

2008

Journal of Lipid Research

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“…Maggio, Fanani and coworkers have reported detailed fluorescence microscopy studies of the enzymatic generation of Cer in SM monolayers in the liquid-expanded (LE) phase at the air-water interface [9,51,[54][55][56]. Their work represents one of the most comprehensive examinations of the factors that influence membrane reorganization during and after SMase activity.…”

Section: Complex Morphologies For Sphingomyelin-ceramide Monolayersmentioning

confidence: 99%

“…The monolayer studies described above illustrate the complex interplay between monolayer morphology and enzyme activity and raise several mechanistic questions that have been addressed during the last two years [54][55][56]. The correlation between the formation of Cer-enriched domains and the development of full catalytic capacity at the end of the lag period was examined [56].…”

Section: Complex Morphologies For Sphingomyelin-ceramide Monolayersmentioning

confidence: 99%

“…The correlation between the formation of Cer-enriched domains and the development of full catalytic capacity at the end of the lag period was examined [56]. The transition from a precatalytic state to full catalytic capacity depended strongly on the extent of the interface between LE and LC phases, leading to the conclusion that the amount of lateral interface provided by the Cerrich domains is one of the main parameters that allows the enzyme to attain full activity.…”

Section: Complex Morphologies For Sphingomyelin-ceramide Monolayersmentioning

confidence: 99%

“…Several aspects of the SMase hydrolysis of SM monolayers suggest that enzymatic reaction leads to monolayer morphologies that are far from equilibrium [54][55][56]. These include the observation of different shapes and sizes for Cer-enriched domains prepared by direct mixing and enzyme action and the formation of a supersaturated Cerenriched phase during the initial lag period.…”

Section: Complex Morphologies For Sphingomyelin-ceramide Monolayersmentioning

confidence: 99%

See 2 more Smart Citations

Ceramide-enriched microdomains in planar membranes

Zou

Johnston

2010

Current Opinion in Colloid & Interface Science

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Composition-driven Surface Domain Structuring Mediated by Sphingolipids and Membrane-active Proteins

Maggio

Borioli

Boca

et al. 2007

Cell Biochem Biophys

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Biomembranes contain a wide variety of lipids and proteins within an essentially two-dimensional structure. The coexistence of such a large number of molecular species causes local tensions that frequently relax into a phase or compositional immiscibility along the lateral and transverse planes of the interface. As a consequence, a substantial microheterogeneity of the surface topography develops and that depends not only on the lipid-protein composition, but also on the lateral and transverse tensions generated as a consequence of molecular interactions. The presence of proteins, and immiscibility among lipids, constitute major perturbing factors for the membrane sculpturing both in terms of its surface topography and dynamics. In this work, we will summarize some recent evidences for the involvement of membrane-associated, both extrinsic and amphitropic, proteins as well as membrane-active phosphohydrolytic enzymes and sphingolipids in driving lateral segregation of phase domains thus determining long-range surface topography.

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The initial surface composition and topography modulate sphingomyelinase-driven sphingomyelin to ceramide conversion in lipid monolayers

Cited by 18 publications

References 40 publications

Sphingomyelinase acts by an area-activated mechanism on the liquid-expanded phase of sphingomyelin monolayers

Sphingomyelinase acts by an area-activated mechanism on the liquid-expanded phase of sphingomyelin monolayers

Ceramide-enriched microdomains in planar membranes

Composition-driven Surface Domain Structuring Mediated by Sphingolipids and Membrane-active Proteins

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