Recycling of Membranes
The living organism plasma membrane needs transport vesicles for synthesis, maintenance, and various physiological functions of the cell, which are dynamic structures and are constantly formed at the specific region of endoplasmic reticulum and Golgi complex membrane. The vesicles may be uncoated or coated vesicles depending on their outer components. The coated vesicles have COPI, COPII, or clathrin coat proteins on the outer side of vesicles. The mechanism of transport may be secretary, called exocytosis or the freight is internalized by endocytosis. The pathogenic viruses like influenza virus and bacterial toxins like shiga toxins also depend on clathrin-coated vesicles for their internalization into host cell. When clathrin coat is removed from vesicles after endocytosis, the vesicle is called early endosomes, whose function is to sort out all the receptors, proteins, and other molecules of the freight. The internalization of freight of molecules may also be mediated by tubular or ring-shaped membrane endosomes, depending on small GTP binding protein cyclin-dependent kinase (CDC42), ADP-ribosylation factor 1 (ARF1), GTPase regulator associated with focal adhesion kinase 1(GTPase activating protein for Rho, GRAF1), cholesterol, and actin. Recently identified exomer protein complex is a putative coat and freight adapter like AP2, which directly transports freight molecules from trans-Golgi network to plasma membrane in response to environment stress in cell cycle-dependent manner. Exocytosis is an important mechanism for neurotransmitters release for communication at synapse. The mechanism of various type vesicles formation, recycling, and their role in transport has been discussed in this chapter.
- Fang Q, Lindau M (2014) How could SNARE proteins open a fusion pore? Physiology 29(4):278–285Google Scholar
- Fang Q, Zhao Y, Lindau M (2013) Juxtamembrane tryptophans of synaptobrevin 2 control the process of membrane fusion. FEBS Lett 587:67–72. https://doi.org/10.1016/j.febslet.2012.11.002
- Ungermann C, Langosch D (2005) Functions of SNAREs in intracellular membrane fusion and lipid bilayer mixing. J Cell Sci 118:3819–3828Google Scholar