Dictionary - Cell: Vesicles (endosome) - The Human Protein Atlas

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On the welcome page of the dictionary, four major sections are shown: Normal tissues, Cancer, Cell structure and Protein expression. Below the image of each section are links to introductory texts for i) normal tissue histology, ii) hallmarks of cancer, and iii) cell structure overview. For the cancer-section there is also a link to current cancer statistics (incidence, survival, etc) for Sweden and the rest of the world. Below the Protein expression section there is a list of genes with links to examples of different protein expression patterns. Within each section there are direct links to histology descriptions of different tissue types and tumor forms as well as descriptions of cell structures.

For the 'Tissue & cell types' and 'Tumors' sections, tissue-slides stained with hematoxylin and eosin (HE) are shown at three different levels of magnification. On the top level, an overview of the whole tissue-sample is shown with boxes in black indicating where zoomed-in representative parts of the tissue are available for viewing. Clicking on these boxes will zoom in on that part to show tissue structures, cells and features in greater detail. Throughout these sections, arrows indicate relevant tissue structures, cell-types and other features.

For the 'Cell structure' section, immunofluorescent images of formaldehyde-fixed cell lines are shown. The various cell structures that are demonstrated are always shown in the green channel using an antibody found in the Human Protein Atlas. The antibody name is linked to the subcellular location summary page of the target gene. The other channels: nucleus, microtubules and endoplasmic reticulum, are always shown in the blue, red and yellow channels, respectively. The channels can be toggled on and off by clicking on the respective coloured button above the image. When applicable, the immunofluorescent images are complemented by immunohistochemically stained cells where the location of the particular cell structure is shown in brown.

For the 'Protein expression' section, tissue slides representing both normal and cancer tissue have been stained using immunohistochemistry to visualize various protein expression patterns. Antibodies have been selected to demonstrate the expression patterns of well-known proteins and to reflect antibodies used in clinical diagnostics to determine the nature of a given cancer. For certain antibodies the corresponding protein expression pattern is shown in both normal and cancer tissues. For each exemplified protein there is a short descriptive text including also the clinical usefulness of the corresponding antibody.

A common feature for all sections is that a general descriptive text about the tissue, tumor-type, cell structure or protein/antibody is provided when browsing a particular topic.

Dictionary > Cell structure > Vesicles (endosome)

Staining of endosome in human cell line U-2 OS

Vesicles

Vesicle is a collective term for a number of different, small membrane-bound organelles. They are often involved in the intracellular transport of proteins and membranes between organelles and in the release of substances to the outside of the cells, or have specialized metabolic functions. Four examples of vesicles that are commonly found in the human cell are listed below.

Endosomes are the main organelles for sorting material that has been taken up from the exterior of the cell by the plasma membrane (endocytosis). The endosomes can then either recycle its contents by bringing it back to the plasma membrane or degrade it by fusing with a lysosome.

Lysosomes are filled with hydrolytic enzymes and are responsible for degrading molecules within the cell. They can fuse with late endosomes, creating so-called endolysosomes, which degrade the material within the endosome.

Peroxisomes contain enzymes that are linked to various metabolic pathways. Especially the breakdown of fatty acids is one of their major functions. Peroxisomes are also the organelle where hydrogen peroxide is degraded and used for other biochemical reactions, e.g. the oxidation of phenols or alcohol.

Lipid droplets are specialized organelles for the cellular storage of neutral lipids. They are of various size and have a unique structure consisting of a hydrophobic core containing the lipids, and a surrounding phospholipid monolayer with attached proteins.

Immunofluorescent staining

Vesicle staining can usually be seen as small, bright dots or circles. It is difficult to identify a type of vesicle solely based on the staining pattern, however they vary in their size, number, and distribution within the cytoplasm: endosomes are usually located close to the nucleus and the Golgi apparatus. Lysosomes are also often located close to the Golgi apparatus, but they are larger and more densely stained. Peroxisomes are spread throughout the cell and are sometimes elongated. Staining of lipid droplet proteins results in a typical ring-like pattern.

Although the staining pattern can indicate toward a type of vesicle, there is no certainty without further validation by other methods like co-localization with typical marker proteins. Therefore, the annotation "vesicles" in the Human Protein Atlas does not distinguish between the different types of vesicles.