Ras protein signal transduction

Definition

Target type: biologicalprocess

An intracellular signaling cassette in which a small monomeric GTPase of the Ras subfamily relays a signal. [GOC:bf]

Ras proteins are small GTPases that act as molecular switches in signal transduction pathways. They cycle between an inactive GDP-bound state and an active GTP-bound state. In their active state, Ras proteins activate downstream effector proteins, including kinases, adaptor proteins, and exchange factors, that relay signals to various cellular processes, such as proliferation, differentiation, and survival.

The Ras signaling pathway is initiated by the binding of a growth factor or other extracellular ligand to its receptor tyrosine kinase (RTK) on the cell surface. This binding triggers a cascade of phosphorylation events that activate the Ras guanine nucleotide exchange factor (GEF), which in turn promotes the exchange of GDP for GTP on Ras, activating the protein.

Once activated, Ras binds to and activates downstream effector proteins, such as the Raf kinase. Raf is a serine/threonine kinase that activates the MEK (MAPK/ERK kinase) kinase, which in turn activates the ERK (extracellular signal-regulated kinase) kinase. ERK phosphorylates various transcription factors, such as Elk-1 and c-Jun, leading to the activation of gene expression.

The Ras signaling pathway is tightly regulated to prevent uncontrolled cell growth. This regulation is achieved through the action of GTPase-activating proteins (GAPs) that promote the hydrolysis of GTP to GDP, deactivating Ras. Additionally, negative feedback loops within the pathway also contribute to its regulation.

Mutations in Ras genes are commonly found in human cancers. These mutations often lead to the production of constitutively active Ras proteins that are unable to be deactivated. This results in uncontrolled cell growth and tumor formation.

In summary, the Ras protein signal transduction pathway is a complex signaling cascade that plays a critical role in regulating cell growth and proliferation. This pathway is highly regulated and mutations in Ras genes can lead to cancer. The pathway involves a series of protein interactions and phosphorylation events that ultimately lead to the activation of transcription factors and the regulation of gene expression.'
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Proteins (23)

Compounds (3,282)