Human Osteosarcoma Epithelial Cells with DsRed ER

The endoplasmic reticulum (ER) is one of three components of the GERL system, the Golgi apparatus and the lysosomes being the others. All 3 have key roles in the function of the cell. The ER is a membrane-bound organelle of labyrinthine, interconnected flattened sacs or tubules that runs through the cytoplasm. The Golgi apparatus is composed of membrane-bound stacks of cisternae and packages molecules like proteins into vesicles for secretion around the cell. Lysosomes are organelles found in the cytoplasm of most cells and possess powerful digestive enzymes such as lysozymes. In the digital video presented above, human osteosarcoma epithelial cells (U2OS line) are expressing a fusion of DsRed2 fluorescent protein to an endoplasmic reticulum targeting signal.

Proteins synthesized within the endoplasmic reticulum (ER) are transported to the Golgi apparatus. Portions of the ER are pinched off, forming transport vesicles which carry their load of proteins to this destination. The membrane of the transport vesicle fuses with the membrane of the Golgi apparatus, merging their contents. Further steps of glycosylation—the addition of saccharides to proteins and lipids—may occur within the Golgi apparatus. The exact pattern of glycosylation determines the final destination of the proteins. In the digital video presented above, human osteosarcoma epithelial cells (U2OS line) are expressing a fusion of DsRed2 fluorescent protein to an endoplasmic reticulum targeting signal.

The endoplasmic reticulum (ER) is responsible for the production of the protein and lipid components of most of the cell’s organelles. The ER contains numerous folds but the membrane forms a single sheet enclosing a single closed sac and this internal space is called the ER lumen. Most secreted and membrane proteins of eukaryotic cells undergo maturation steps in the lumen which is part of the same compartment as the nuclear envelope—the double membrane of the nucleus that encloses genetic material in eukaryotic cells. In the digital video presented above, human osteosarcoma epithelial cells (U2OS line) are expressing a fusion of DsRed2 fluorescent protein to an endoplasmic reticulum targeting signal.