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Detergent-resistant membrane microdomains from Caco-2 cells do not contain caveolin
C Mirre1, L Monlauzeur, M Garcia
1Institut de Biologie du Développement de Marseille, Faculté des Sciences de Luminy, Marseille, France.
The American Journal of Physiology
|September 1, 1996
Summary
Detergent-resistant microdomains in Caco-2 cells share molecular traits with caveolae but lack caveolin and distinct structures. Caveolin is not essential for sorting glycosyl phosphatidylinositol-anchored proteins to the apical membrane.
Area of Science:
- Cell Biology
- Membrane Biology
- Biochemistry
Background:
- Detergent-resistant microdomains (DRMs) are membrane domains implicated in various cellular functions.
- Caveolae are specific types of DRMs, flask-shaped invaginations of the plasma membrane, typically rich in caveolin.
- The relationship between DRMs and caveolae, particularly in cell types lacking caveolin, remains incompletely understood.
Purpose of the Study:
- To investigate the relationship between detergent-resistant microdomains and caveolae in Caco-2 cells.
- To determine the molecular composition of DRMs in Caco-2 cells lacking caveolin.
- To assess the role of caveolin in the sorting of glycosyl phosphatidylinositol (GPI)-anchored proteins.
Main Methods:
- Western blotting and Northern blotting to detect caveolin expression.
- Immunoprecipitation assays to confirm caveolin presence.
- Electron microscopy to visualize membrane structures.
- Sucrose gradient ultracentrifugation to analyze DRM properties.
- Analysis of protein enrichment in DRMs.
Main Results:
- Caveolin was undetectable in Caco-2 cells, unlike in A431 cells.
- DRMs from Caco-2 and A431 cells exhibited similar morphological characteristics and buoyant densities.
- Caco-2 cell DRMs were enriched in GPI-anchored proteins, sucrase-isomaltase, and proteins typically found in caveolin-rich membranes.
- Morphologically identifiable caveolae were absent in Caco-2 cells but present in A431 cells.
- Caveolin was not required for the apical sorting of GPI-linked proteins in Caco-2 cells.
Conclusions:
- Detergent-resistant microdomains in Caco-2 cells possess a molecular composition similar to caveolin-rich microdomains but do not originate from morphologically identified caveolae.
- Caveolin is not a necessary component for the formation or function of these specific DRMs or for the apical localization of GPI-anchored proteins in Caco-2 cells.