Limits...
Endocytosis via caveolae: alternative pathway with distinct cellular compartments to avoid lysosomal degradation?

Kiss AL, Botos E - J. Cell. Mol. Med. (2009)

Bottom Line: Endocytosis--the uptake of extracellular ligands, soluble molecules, protein and lipids from the extracellular surface--is a vital process, comprising multiple mechanisms, including phagocytosis, macropinocytosis, clathrin-dependent and clathrin-independent uptake such as caveolae-mediated and non-caveolar raft-dependent endocytosis.The best-studied endocytotic pathway for internalizing both bulk membrane and specific proteins is the clathrin-mediated endocytosis.We are especially focussing on the intracellular route of caveolae and providing data supporting that caveolar endocytosis can join to the classical endocytotic pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Morphology and Developmental Biology, Semmelweis University, Budapest, Hungary. KissA@ana2.sote.hu

ABSTRACT
Endocytosis--the uptake of extracellular ligands, soluble molecules, protein and lipids from the extracellular surface--is a vital process, comprising multiple mechanisms, including phagocytosis, macropinocytosis, clathrin-dependent and clathrin-independent uptake such as caveolae-mediated and non-caveolar raft-dependent endocytosis. The best-studied endocytotic pathway for internalizing both bulk membrane and specific proteins is the clathrin-mediated endocytosis. Although many papers were published about the caveolar endocytosis, it is still not known whether it represents an alternative pathway with distinct cellular compartments to avoid lysosomal degradation or ligands taken up by caveolae can also be targeted to late endosomes/lysosomes. In this paper, we summarize data available about caveolar endocytosis. We are especially focussing on the intracellular route of caveolae and providing data supporting that caveolar endocytosis can join to the classical endocytotic pathway.

Show MeSH

Related in: MedlinePlus

Using Ruthenium red (Ru red) to label the cell surface, single vesicles (arrows) as well as caveolar clusters (arrowheads) are found to be Ru red-positive. This finding indicates that they are still in connection with the cell surface. Note that many of the vesicles deeper in the cytoplasm are also labelled with Ru red showing that they are still connected with the cell surface. The caveolar clusters (arrowheads) are often described as caveosomes. The Ru red staining clearly shows that many of them are not independent structures. pm: plasma membrane. Bars: 400 nm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4496137&req=5

fig03: Using Ruthenium red (Ru red) to label the cell surface, single vesicles (arrows) as well as caveolar clusters (arrowheads) are found to be Ru red-positive. This finding indicates that they are still in connection with the cell surface. Note that many of the vesicles deeper in the cytoplasm are also labelled with Ru red showing that they are still connected with the cell surface. The caveolar clusters (arrowheads) are often described as caveosomes. The Ru red staining clearly shows that many of them are not independent structures. pm: plasma membrane. Bars: 400 nm.

Mentions: There are data, however, showing that ligands internalized by cavolae can be driven to the classical endocytotic organelles. Cholera toxin entering the cells by caveolar endocytosis passes through early endosomes and accumulates in the Golgi complex [70]. It was also shown that under normal conditions, caveolae carrying SV40 virus particles can transiently interact with early endosomes [71, 72]. The existence of two caveolar trafficking routes involving caveosomes and early endosomes raises the questions whether caveosomes are independent structures or the downstream caveosomes interact with the classical endocytotic compartments. When we studied caveolar internalization in HepG2 cells, we found that many of these caveosome-like multi-caveolar complexes were connected with the cell surface by a narrow tubular plasma membrane invaginations (Fig. 2B and C), but some of them seemed to be independent structures in the cytoplasm. When Ruthenium red (Ru red) – an electron dense dye – was used to label the cell surface, many of these structures were Ru red–positive (Fig. 3A–C) indicating that they were still connected with the cell surface. These results support the idea that a significant portion of these multi-caveolar complexes described as caveosomes are not independent structures.


Endocytosis via caveolae: alternative pathway with distinct cellular compartments to avoid lysosomal degradation?

Kiss AL, Botos E - J. Cell. Mol. Med. (2009)

Using Ruthenium red (Ru red) to label the cell surface, single vesicles (arrows) as well as caveolar clusters (arrowheads) are found to be Ru red-positive. This finding indicates that they are still in connection with the cell surface. Note that many of the vesicles deeper in the cytoplasm are also labelled with Ru red showing that they are still connected with the cell surface. The caveolar clusters (arrowheads) are often described as caveosomes. The Ru red staining clearly shows that many of them are not independent structures. pm: plasma membrane. Bars: 400 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4496137&req=5

fig03: Using Ruthenium red (Ru red) to label the cell surface, single vesicles (arrows) as well as caveolar clusters (arrowheads) are found to be Ru red-positive. This finding indicates that they are still in connection with the cell surface. Note that many of the vesicles deeper in the cytoplasm are also labelled with Ru red showing that they are still connected with the cell surface. The caveolar clusters (arrowheads) are often described as caveosomes. The Ru red staining clearly shows that many of them are not independent structures. pm: plasma membrane. Bars: 400 nm.
Mentions: There are data, however, showing that ligands internalized by cavolae can be driven to the classical endocytotic organelles. Cholera toxin entering the cells by caveolar endocytosis passes through early endosomes and accumulates in the Golgi complex [70]. It was also shown that under normal conditions, caveolae carrying SV40 virus particles can transiently interact with early endosomes [71, 72]. The existence of two caveolar trafficking routes involving caveosomes and early endosomes raises the questions whether caveosomes are independent structures or the downstream caveosomes interact with the classical endocytotic compartments. When we studied caveolar internalization in HepG2 cells, we found that many of these caveosome-like multi-caveolar complexes were connected with the cell surface by a narrow tubular plasma membrane invaginations (Fig. 2B and C), but some of them seemed to be independent structures in the cytoplasm. When Ruthenium red (Ru red) – an electron dense dye – was used to label the cell surface, many of these structures were Ru red–positive (Fig. 3A–C) indicating that they were still connected with the cell surface. These results support the idea that a significant portion of these multi-caveolar complexes described as caveosomes are not independent structures.

Bottom Line: Endocytosis--the uptake of extracellular ligands, soluble molecules, protein and lipids from the extracellular surface--is a vital process, comprising multiple mechanisms, including phagocytosis, macropinocytosis, clathrin-dependent and clathrin-independent uptake such as caveolae-mediated and non-caveolar raft-dependent endocytosis.The best-studied endocytotic pathway for internalizing both bulk membrane and specific proteins is the clathrin-mediated endocytosis.We are especially focussing on the intracellular route of caveolae and providing data supporting that caveolar endocytosis can join to the classical endocytotic pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Morphology and Developmental Biology, Semmelweis University, Budapest, Hungary. KissA@ana2.sote.hu

ABSTRACT
Endocytosis--the uptake of extracellular ligands, soluble molecules, protein and lipids from the extracellular surface--is a vital process, comprising multiple mechanisms, including phagocytosis, macropinocytosis, clathrin-dependent and clathrin-independent uptake such as caveolae-mediated and non-caveolar raft-dependent endocytosis. The best-studied endocytotic pathway for internalizing both bulk membrane and specific proteins is the clathrin-mediated endocytosis. Although many papers were published about the caveolar endocytosis, it is still not known whether it represents an alternative pathway with distinct cellular compartments to avoid lysosomal degradation or ligands taken up by caveolae can also be targeted to late endosomes/lysosomes. In this paper, we summarize data available about caveolar endocytosis. We are especially focussing on the intracellular route of caveolae and providing data supporting that caveolar endocytosis can join to the classical endocytotic pathway.

Show MeSH
Related in: MedlinePlus