ras proteins: biological effects and biochemical targets (review)

Ras genes are an ubiquitous eukaryotic gene family. Since their discovery as the cellular homologues of the transforming genes of Harvey and Kirsten retroviruses, ras genes have been presumed to play a role in growth control, mainly because of their potential to induce uncontrolled cell proliferation. This notion is strongly supported by recent evidence indicating that ras mutations may be causative or closely linked to the onset of some types of human tumors. However, the mechanism of action of ras proteins in mammalian cells is poorly understood. Using the microinjection technique as a biological assay for ras proteins, it has been possible to address several important questions concerning cellular and biochemical aspects of ras function. When introduced into living cells by microinjection, purified ras proteins can induce cell proliferation, neuronal differentiation, oocyte maturation, and exocytotic degranulation. On the biochemical level, microinjection studies indicated that ras proteins can induce specific alterations in phospholipid metabolism.