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Definition of Arabidopsis sterol-rich membrane microdomains by differential treatment with methyl-beta-cyclodextrin and quantitative proteomics.

Kierszniowska S, Seiwert B, Schulze WX - Mol. Cell Proteomics (2008)

Bottom Line: Among the sterol-dependent proteins we found an over-representation of glycosylphosphatidylinositol-anchored proteins.Predominantly proteins with signaling functions, such as receptor kinases, G-proteins, and calcium signaling proteins, were identified as variable members in plant lipid rafts, whereas cell wall-related proteins and specific proteins with unknown functions make up a core set of sterol-dependent plant plasma membrane proteins.This allows the plant to maintain a balance between static anchoring of cell shape forming elements and variable adjustment to changing external conditions.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany.

ABSTRACT
Plasma membranes are dynamic compartments with key functions in solute transport, cell shape, and communication between cells and the environment. In mammalian cells and yeast, the plasma membrane has been shown to be compartmented into so-called lipid rafts, which are defined by their resistance to treatment with non-ionic detergents. In plants, the existence of lipid rafts has been postulated, but the precise composition of this membrane compartment is still under debate. Here we were able to experimentally clearly distinguish (i) true sterol-dependent "raft proteins" and (ii) sterol-independent "non-raft" proteins and co-purifying "contaminants" in plant detergent-resistant membranes. We used quantitative proteomics techniques involving (15)N metabolic labeling and specific disruption of sterol-rich membrane domains by methyl-beta-cyclodextrin. Among the sterol-dependent proteins we found an over-representation of glycosylphosphatidylinositol-anchored proteins. A large fraction of these proteins has functions in cell wall anchoring. We were able to distinguish constant and variable components of plant sterol-rich membrane microdomains based on their responsiveness to the drug methyl-beta-cyclodextrin. Predominantly proteins with signaling functions, such as receptor kinases, G-proteins, and calcium signaling proteins, were identified as variable members in plant lipid rafts, whereas cell wall-related proteins and specific proteins with unknown functions make up a core set of sterol-dependent plant plasma membrane proteins. This allows the plant to maintain a balance between static anchoring of cell shape forming elements and variable adjustment to changing external conditions.

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A box plot of the deviations from the mean ratio change upon mβcd treatment for each protein in the functional categories “cell wall-related,” “lipid-modifying,” and “vesicle trafficking” as well as for signaling proteins in “receptor kinases,” “calcium signaling,” and “G-protein signaling” across four independent reciprocal experiments is shown. Proteins were classified according to the MapMan classification scheme for plant proteins (34).
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f6: A box plot of the deviations from the mean ratio change upon mβcd treatment for each protein in the functional categories “cell wall-related,” “lipid-modifying,” and “vesicle trafficking” as well as for signaling proteins in “receptor kinases,” “calcium signaling,” and “G-protein signaling” across four independent reciprocal experiments is shown. Proteins were classified according to the MapMan classification scheme for plant proteins (34).

Mentions: The identified proteins with signaling functions (receptor-like kinases, calcium signaling proteins, and G-protein signaling proteins) showed a larger experiment-to-experiment deviation from the mean ratio change upon mβcd treatment than did proteins in the functional category of cell wall, lipid-modifying, and vesicle trafficking (Fig. 6). Thus, the effect of mβcd on signaling proteins is significantly more variable for the different proteins within a functional category and independent experimental sets compared with the effect of mβcd on cell wall or lipid-modifying proteins. This is a strong indication for different classes of mβcd-responsive (i.e. sterol-dependent) proteins. We propose that the variability of the mβcd response among signaling proteins is an indication for a more variable and condition-dependent association of signaling proteins with sterol-rich membrane microdomains.


Definition of Arabidopsis sterol-rich membrane microdomains by differential treatment with methyl-beta-cyclodextrin and quantitative proteomics.

Kierszniowska S, Seiwert B, Schulze WX - Mol. Cell Proteomics (2008)

A box plot of the deviations from the mean ratio change upon mβcd treatment for each protein in the functional categories “cell wall-related,” “lipid-modifying,” and “vesicle trafficking” as well as for signaling proteins in “receptor kinases,” “calcium signaling,” and “G-protein signaling” across four independent reciprocal experiments is shown. Proteins were classified according to the MapMan classification scheme for plant proteins (34).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2667346&req=5

f6: A box plot of the deviations from the mean ratio change upon mβcd treatment for each protein in the functional categories “cell wall-related,” “lipid-modifying,” and “vesicle trafficking” as well as for signaling proteins in “receptor kinases,” “calcium signaling,” and “G-protein signaling” across four independent reciprocal experiments is shown. Proteins were classified according to the MapMan classification scheme for plant proteins (34).
Mentions: The identified proteins with signaling functions (receptor-like kinases, calcium signaling proteins, and G-protein signaling proteins) showed a larger experiment-to-experiment deviation from the mean ratio change upon mβcd treatment than did proteins in the functional category of cell wall, lipid-modifying, and vesicle trafficking (Fig. 6). Thus, the effect of mβcd on signaling proteins is significantly more variable for the different proteins within a functional category and independent experimental sets compared with the effect of mβcd on cell wall or lipid-modifying proteins. This is a strong indication for different classes of mβcd-responsive (i.e. sterol-dependent) proteins. We propose that the variability of the mβcd response among signaling proteins is an indication for a more variable and condition-dependent association of signaling proteins with sterol-rich membrane microdomains.

Bottom Line: Among the sterol-dependent proteins we found an over-representation of glycosylphosphatidylinositol-anchored proteins.Predominantly proteins with signaling functions, such as receptor kinases, G-proteins, and calcium signaling proteins, were identified as variable members in plant lipid rafts, whereas cell wall-related proteins and specific proteins with unknown functions make up a core set of sterol-dependent plant plasma membrane proteins.This allows the plant to maintain a balance between static anchoring of cell shape forming elements and variable adjustment to changing external conditions.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany.

ABSTRACT
Plasma membranes are dynamic compartments with key functions in solute transport, cell shape, and communication between cells and the environment. In mammalian cells and yeast, the plasma membrane has been shown to be compartmented into so-called lipid rafts, which are defined by their resistance to treatment with non-ionic detergents. In plants, the existence of lipid rafts has been postulated, but the precise composition of this membrane compartment is still under debate. Here we were able to experimentally clearly distinguish (i) true sterol-dependent "raft proteins" and (ii) sterol-independent "non-raft" proteins and co-purifying "contaminants" in plant detergent-resistant membranes. We used quantitative proteomics techniques involving (15)N metabolic labeling and specific disruption of sterol-rich membrane domains by methyl-beta-cyclodextrin. Among the sterol-dependent proteins we found an over-representation of glycosylphosphatidylinositol-anchored proteins. A large fraction of these proteins has functions in cell wall anchoring. We were able to distinguish constant and variable components of plant sterol-rich membrane microdomains based on their responsiveness to the drug methyl-beta-cyclodextrin. Predominantly proteins with signaling functions, such as receptor kinases, G-proteins, and calcium signaling proteins, were identified as variable members in plant lipid rafts, whereas cell wall-related proteins and specific proteins with unknown functions make up a core set of sterol-dependent plant plasma membrane proteins. This allows the plant to maintain a balance between static anchoring of cell shape forming elements and variable adjustment to changing external conditions.

Show MeSH