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Diversity of raft-like domains in late endosomes.

Sobo K, Chevallier J, Parton RG, Gruenberg J, van der Goot FG - PLoS ONE (2007)

Bottom Line: Late endosomes, the last sorting station in the endocytic pathway before lysosomes, are pleiomorphic organelles composed of tubular elements as well as vesicular regions with a characteristic multivesicular appearance, which play a crucial role in intracellular trafficking.Interestingly, these differentially localized domains vary in protein composition and physico-chemical properties.Implications of these findings for late endosomal functions are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.

ABSTRACT

Background: Late endosomes, the last sorting station in the endocytic pathway before lysosomes, are pleiomorphic organelles composed of tubular elements as well as vesicular regions with a characteristic multivesicular appearance, which play a crucial role in intracellular trafficking. Here, we have investigated whether, in addition to these morphologically distinguishable regions, late endosomal membranes are additionally sub-compartmentalized into membrane microdomains.

Methodology/principal findings: Using sub-organellar fractionation techniques, both with and without detergents, combined with electron microscopy, we found that both the limiting membrane of the organel and the intraluminal vesicles contain raft-type membrane domains. Interestingly, these differentially localized domains vary in protein composition and physico-chemical properties.

Conclusions/significance: In addition to the multivesicular organization, we find that late endosomes contain cholesterol rich microdomains both on their limiting membrane and their intraluminal vesicles that differ in composition and properties. Implications of these findings for late endosomal functions are discussed.

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Related in: MedlinePlus

Detection of two types of late endosomal DRMs.Late endosomes from BHK cells were submitted to solubilization in 1% Triton X-100 either at 4°C or at 37°C. The lysat was subsequently analyzed on an Optiprep gradient and 6 fractions were collected from the top. The total of each fraction was submitted to SDS-PAGE and Western blotting to detect flotillin-1 or to an aerolysin overlay to reveal GPI-anchored proteins.
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pone-0000391-g003: Detection of two types of late endosomal DRMs.Late endosomes from BHK cells were submitted to solubilization in 1% Triton X-100 either at 4°C or at 37°C. The lysat was subsequently analyzed on an Optiprep gradient and 6 fractions were collected from the top. The total of each fraction was submitted to SDS-PAGE and Western blotting to detect flotillin-1 or to an aerolysin overlay to reveal GPI-anchored proteins.

Mentions: Despite the rather harsh solubilization step (higher detergent to protein ratio than for the preparation of DRMs from whole cells), DRMs isolated from late endosomes contained 40% of the total organellar cholesterol. We therefore wondered whether these domains were particularly resistant to solubilization and therefore performed the solubilization at 37°C. This treatment led to the solubilization of GPI-anchored proteins, but interestingly not to that of flotillin-1 (Fig. 3), suggestive of a differential distribution. Whereas, GPI-anchored proteins and flotillin-1 could be part of the same domain, one being on the periphery and the other in the center, as proposed for prion protein and thy-1 [56], [57], they could also reside on spatially segregated domains. Since late endosomes contain internal vesicles, one attractive possibility is that GPI-anchored proteins and flotillin-1 differentially distribute to the internal and limiting membranes of the organelle.


Diversity of raft-like domains in late endosomes.

Sobo K, Chevallier J, Parton RG, Gruenberg J, van der Goot FG - PLoS ONE (2007)

Detection of two types of late endosomal DRMs.Late endosomes from BHK cells were submitted to solubilization in 1% Triton X-100 either at 4°C or at 37°C. The lysat was subsequently analyzed on an Optiprep gradient and 6 fractions were collected from the top. The total of each fraction was submitted to SDS-PAGE and Western blotting to detect flotillin-1 or to an aerolysin overlay to reveal GPI-anchored proteins.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1851096&req=5

pone-0000391-g003: Detection of two types of late endosomal DRMs.Late endosomes from BHK cells were submitted to solubilization in 1% Triton X-100 either at 4°C or at 37°C. The lysat was subsequently analyzed on an Optiprep gradient and 6 fractions were collected from the top. The total of each fraction was submitted to SDS-PAGE and Western blotting to detect flotillin-1 or to an aerolysin overlay to reveal GPI-anchored proteins.
Mentions: Despite the rather harsh solubilization step (higher detergent to protein ratio than for the preparation of DRMs from whole cells), DRMs isolated from late endosomes contained 40% of the total organellar cholesterol. We therefore wondered whether these domains were particularly resistant to solubilization and therefore performed the solubilization at 37°C. This treatment led to the solubilization of GPI-anchored proteins, but interestingly not to that of flotillin-1 (Fig. 3), suggestive of a differential distribution. Whereas, GPI-anchored proteins and flotillin-1 could be part of the same domain, one being on the periphery and the other in the center, as proposed for prion protein and thy-1 [56], [57], they could also reside on spatially segregated domains. Since late endosomes contain internal vesicles, one attractive possibility is that GPI-anchored proteins and flotillin-1 differentially distribute to the internal and limiting membranes of the organelle.

Bottom Line: Late endosomes, the last sorting station in the endocytic pathway before lysosomes, are pleiomorphic organelles composed of tubular elements as well as vesicular regions with a characteristic multivesicular appearance, which play a crucial role in intracellular trafficking.Interestingly, these differentially localized domains vary in protein composition and physico-chemical properties.Implications of these findings for late endosomal functions are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.

ABSTRACT

Background: Late endosomes, the last sorting station in the endocytic pathway before lysosomes, are pleiomorphic organelles composed of tubular elements as well as vesicular regions with a characteristic multivesicular appearance, which play a crucial role in intracellular trafficking. Here, we have investigated whether, in addition to these morphologically distinguishable regions, late endosomal membranes are additionally sub-compartmentalized into membrane microdomains.

Methodology/principal findings: Using sub-organellar fractionation techniques, both with and without detergents, combined with electron microscopy, we found that both the limiting membrane of the organel and the intraluminal vesicles contain raft-type membrane domains. Interestingly, these differentially localized domains vary in protein composition and physico-chemical properties.

Conclusions/significance: In addition to the multivesicular organization, we find that late endosomes contain cholesterol rich microdomains both on their limiting membrane and their intraluminal vesicles that differ in composition and properties. Implications of these findings for late endosomal functions are discussed.

Show MeSH
Related in: MedlinePlus