Identifying a key growth factor in cell proliferation
Mitochondria are well known for their role as powerhouses in our cells, using respiration to release the energy in the food we eat and trapping that energy in the molecule adenosine triphosphate, or ATP. In two companion papers published this week in Cell, MIT researchers reveal why proliferating cells — including those in tumors — require mitochondrial respiration. While there are other ways to make ATP, cells can’t proliferate without access to electron acceptors provided by respiration. For proliferating cells, there must be plenty of aspartate present to create all of the new cell’s RNA and DNA, as well as its proteins. Aspartate is an amino acid, one of the fundamental building blocks of proteins, but unlike the others it is not readily available in the bloodstream — indeed, it seems the body may actively limit blood levels of the amino acid — so each mammalian cell has to make its own....