p21ras: an oncoprotein functioning in growth factor-induced signal transduction.
p21ras is a small GTPase that functions as a molecular switch in intracellular signal transduction pathways activated by a large variety of growth factors. In 50% of colorectal tumours, one of the genes for p21ras is mutated resulting in a constitutive active protein. Recently, progress has been made in the elucidation of the signalling pathways in which p21ras is involved. After a ligand binds to growth factor receptors, in particular receptor tyrosine kinases, a guanine nucleotide exchange factor is activated, which results in p21ras in the GTP-bound form. This GTP-bound form of p21ras interacts with the protein kinase raf1 and induces the activation of a kinase cascade, resulting in various cellular responses. This kinase cascade is part of an integrated network of both positive and negative signalling events.
Bos
J L
JL
Laboratory for Physiological Chemistry, Universiteit Utrecht, The Netherlands.
D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006133:Growth Substances / Q000502:physiology*; D006801:Humans; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
D006133:Growth Substances; D020794:Receptor Protein-Tyrosine Kinases; D015689:Oncogene Protein p21(ras)