On releasing tension

摘要

Like life, cells are subject to continuous change. Nothing in the vicinity of a cell remains still - unless death has interrupted its course. And the same goes for the inside of each cell. All sorts of molecules are being shuttled from one part to another, after having been created or on their way to being degraded. The cell membrane is also a very dynamic and supple structure, with molecules wandering through it constantly. One means of transport for shifting molecules around are known as endosomes. Endosomes are formed by the invagination of one part of the cell membrane - like a bubble budding towards the inside of the cell - which is then cleaved and able to float free in the cell's cytoplasm. Invagination then occurs on the surface of the endosomes themselves to form even smaller bubbles - or vesicles - that are in turn also set free. Like endosomes, these inner vesicles are a means of molecular transport too. It's a sort of Russian doll experience... The art of invagination per se may sound simple but it involves a lot of imagination on behalf of biology. Recently, scientists discovered a protein coined Snf7 that is providing hints as to how endosome invagination may occur, and the subsequent creation of vesicles.