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Caveolin 3, flotillin 1 and influenza virus hemagglutinin reside in distinct domains on the sarcolemma of skeletal myofibers.

Kaakinen M, Kaisto T, Rahkila P, Metsikkö K - Biochem Res Int (2012)

Bottom Line: Concomitantly, the water permeability of the sarcolemma increased significantly.These findings indicate that each raft protein exhibits a strictly defined distribution in the sarcolemma.Only the distribution of caveolin 3 that binds cholesterol was exclusively dependent on cholesterol environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, P.O. Box 5000, Aapistie 7, 90014 Oulu, Finland.

ABSTRACT
We examined the distribution of selected raft proteins on the sarcolemma of skeletal myofibers and the role of cholesterol environment in the distribution. Immunofluorescence staining showed that flotillin-1 and influenza hemagglutinin exhibited rafts that located in the domains deficient of the dystrophin glycoprotein complex, but the distribution patterns of the two proteins were different. Cholesterol depletion from the sarcolemma by means of methyl-β-cyclodextrin resulted in distorted caveolar morphology and redistribution of the caveolin 3 protein. Concomitantly, the water permeability of the sarcolemma increased significantly. However, cholesterol depletion did not reshuffle flotillin 1 or hemagglutinin. Furthermore, a hemagglutinin variant that lacked a raft-targeting signals exhibited a similar distribution pattern as the native raft protein. These findings indicate that each raft protein exhibits a strictly defined distribution in the sarcolemma. Only the distribution of caveolin 3 that binds cholesterol was exclusively dependent on cholesterol environment.

No MeSH data available.


Related in: MedlinePlus

Flotillin 1 resides in the DGC-deficient regions in structures near transverse tubule openings. A confocal section at the sarcolemma level indicates that flotillin 1 (a) appears as spots of irregular shape. Double staining for β-dystroglycan (b) and the merged image (c) show that dystroglycan and flotillin 1 do not colocalize. A confocal section at the sarcolemma level indicated that flotillin 1 (d) and DHPR (e) that mark transverse tubules are flanking each other, demonstrated in the merged image (f). A longitudinal confocal section in the middle of a myofiber indicates that flotillin 1 (g) exhibits intense staining that seems to be an extension of the DHPR staining (h) as demonstrated in the merged image (i). Immunoelectron microscopy for flotillin 1 in EDL section shows gold particles (arrowhead) in a structure beneath the sarcolemma near the transverse tubule neck (arrow) (j). Scale bars, 2 μm (a–i); 250 nm (j).
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fig1: Flotillin 1 resides in the DGC-deficient regions in structures near transverse tubule openings. A confocal section at the sarcolemma level indicates that flotillin 1 (a) appears as spots of irregular shape. Double staining for β-dystroglycan (b) and the merged image (c) show that dystroglycan and flotillin 1 do not colocalize. A confocal section at the sarcolemma level indicated that flotillin 1 (d) and DHPR (e) that mark transverse tubules are flanking each other, demonstrated in the merged image (f). A longitudinal confocal section in the middle of a myofiber indicates that flotillin 1 (g) exhibits intense staining that seems to be an extension of the DHPR staining (h) as demonstrated in the merged image (i). Immunoelectron microscopy for flotillin 1 in EDL section shows gold particles (arrowhead) in a structure beneath the sarcolemma near the transverse tubule neck (arrow) (j). Scale bars, 2 μm (a–i); 250 nm (j).

Mentions: The flotillin rafts are distinct from caveolae in mononucleated cells [20] in which the flotillin microdomains can exist in either flat or invaginated state [21]. Here, we examined whether flotillin 1 microdomains in skeletal muscle cells were distinct from the caveolae that contain cav 3. For this purpose, we performed double immunofluorescence staining for the two proteins in isolated myofibers that provide a view over the muscle cell surface. Figures 1(a)–1(c) show that flotillin 1 appeared as clusters at the A-band regions in the domains deficient of DGC. These domains are lacking cav 3 [4].


Caveolin 3, flotillin 1 and influenza virus hemagglutinin reside in distinct domains on the sarcolemma of skeletal myofibers.

Kaakinen M, Kaisto T, Rahkila P, Metsikkö K - Biochem Res Int (2012)

Flotillin 1 resides in the DGC-deficient regions in structures near transverse tubule openings. A confocal section at the sarcolemma level indicates that flotillin 1 (a) appears as spots of irregular shape. Double staining for β-dystroglycan (b) and the merged image (c) show that dystroglycan and flotillin 1 do not colocalize. A confocal section at the sarcolemma level indicated that flotillin 1 (d) and DHPR (e) that mark transverse tubules are flanking each other, demonstrated in the merged image (f). A longitudinal confocal section in the middle of a myofiber indicates that flotillin 1 (g) exhibits intense staining that seems to be an extension of the DHPR staining (h) as demonstrated in the merged image (i). Immunoelectron microscopy for flotillin 1 in EDL section shows gold particles (arrowhead) in a structure beneath the sarcolemma near the transverse tubule neck (arrow) (j). Scale bars, 2 μm (a–i); 250 nm (j).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3303869&req=5

fig1: Flotillin 1 resides in the DGC-deficient regions in structures near transverse tubule openings. A confocal section at the sarcolemma level indicates that flotillin 1 (a) appears as spots of irregular shape. Double staining for β-dystroglycan (b) and the merged image (c) show that dystroglycan and flotillin 1 do not colocalize. A confocal section at the sarcolemma level indicated that flotillin 1 (d) and DHPR (e) that mark transverse tubules are flanking each other, demonstrated in the merged image (f). A longitudinal confocal section in the middle of a myofiber indicates that flotillin 1 (g) exhibits intense staining that seems to be an extension of the DHPR staining (h) as demonstrated in the merged image (i). Immunoelectron microscopy for flotillin 1 in EDL section shows gold particles (arrowhead) in a structure beneath the sarcolemma near the transverse tubule neck (arrow) (j). Scale bars, 2 μm (a–i); 250 nm (j).
Mentions: The flotillin rafts are distinct from caveolae in mononucleated cells [20] in which the flotillin microdomains can exist in either flat or invaginated state [21]. Here, we examined whether flotillin 1 microdomains in skeletal muscle cells were distinct from the caveolae that contain cav 3. For this purpose, we performed double immunofluorescence staining for the two proteins in isolated myofibers that provide a view over the muscle cell surface. Figures 1(a)–1(c) show that flotillin 1 appeared as clusters at the A-band regions in the domains deficient of DGC. These domains are lacking cav 3 [4].

Bottom Line: Concomitantly, the water permeability of the sarcolemma increased significantly.These findings indicate that each raft protein exhibits a strictly defined distribution in the sarcolemma.Only the distribution of caveolin 3 that binds cholesterol was exclusively dependent on cholesterol environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, P.O. Box 5000, Aapistie 7, 90014 Oulu, Finland.

ABSTRACT
We examined the distribution of selected raft proteins on the sarcolemma of skeletal myofibers and the role of cholesterol environment in the distribution. Immunofluorescence staining showed that flotillin-1 and influenza hemagglutinin exhibited rafts that located in the domains deficient of the dystrophin glycoprotein complex, but the distribution patterns of the two proteins were different. Cholesterol depletion from the sarcolemma by means of methyl-β-cyclodextrin resulted in distorted caveolar morphology and redistribution of the caveolin 3 protein. Concomitantly, the water permeability of the sarcolemma increased significantly. However, cholesterol depletion did not reshuffle flotillin 1 or hemagglutinin. Furthermore, a hemagglutinin variant that lacked a raft-targeting signals exhibited a similar distribution pattern as the native raft protein. These findings indicate that each raft protein exhibits a strictly defined distribution in the sarcolemma. Only the distribution of caveolin 3 that binds cholesterol was exclusively dependent on cholesterol environment.

No MeSH data available.


Related in: MedlinePlus