Introduction

SNAREs are proteins that are found on membranes in the cell, including intracellular organelle membranes, vesicles membranes and the plasma membrane.  They are involved in membrane trafficking, they mediate the fusion of membranes.

Eukaryotic cells have numerous intracellular compartments(Golgi, Lysosome, Endoplasmic reticulum (ER), Mitochondria, Endosomes) which carry out different functions in the cell. They need to be able to communicate with one another and this is carried out by intracellular vesicular traffic. The cell also needs to be able to communicate with its environment by taking up substance (endocytosis) and secreting substances (exocytosis), again this is carried out by vesicular traffic.The two pathways for membrane trafficking include:

• Biosynthetic/Secretory pathway - proteins cotranslated from the rough endoplasmic reticulum into the golgi can have postranslational modifications added as they progress through the golgi as can other molecelues produced in the cell. Molecules can then be stored until they are packaged into vesicles for release by exocytosis. There are two components to this part of the pathway regulated secretion and constitutive secretion.
• Endocytic pathways - this takes substances up from the exterior of the cell by endocytosis most often by clathrin coated pits. But there are other types of endocytosis including pinocyctosis,phagocytosis, receptor mediated endocytosis and caveolae.

   herkules.oulu.fi/isbn9514252764/html/c299.html Follow this link to view an overview of both of these pathways.

The vesicles need to fuse to the correct target in order for membrane trafficking to be successful and to maintain organelle compertment specificity, the fusion and the specificity of the fusion is the role of SNARES which requires additional proteins called Rabs.

The first video below gives a breif overview of endocytosis and exocytosis.

The second video gives an overview of protein trafficking through the cell.

The above video on protein trafficking has commentary in english and russian, a version with just english commentary can be found on you tube but it was imcompatible with this website so could not be displayed.