Final answer:
Receptor tyrosine kinases regulate Ras proteins via GTPase-activating proteins and guanine nucleotide-exchange factors, triggering a cascade leading to cellular responses. Activated Ras participates in the MAP kinase pathway, affecting gene expression and cell division. Mutations in Ras can result in uncontrolled proliferation and cancer.
Step-by-step explanation:
The correct relationship between receptor tyrosine kinases (RTKs) and Ras proteins is that tyrosine kinase dimers use GTPase-activating proteins (GAPs) and guanine nucleotide-exchange factors (GNRFs, commonly referred to as GEFs) to regulate Ras proteins. This relationship is a crucial component in the signaling pathway of cell proliferation and differentiation. When a ligand binds to the receptor tyrosine kinase, it causes the receptor to dimerize and autophosphorylate its tyrosine residues. This phosphorylation creates binding sites for proteins with Src homology 2 (SH2) domains and starts a cascade of downstream signaling events. One key event is the activation of Ras—a small GTPase protein. The activated Ras protein then initiates the MAP kinase cascade, ultimately resulting in cellular responses such as gene expression, metabolism, and cell division changes.
One well-known example of receptor tyrosine kinase signaling involves epidermal growth factor receptor (EGFR), where its defects are linked to various neuromuscular diseases. Furthermore, mutations in Ras that affect its GTPase activity lead to the protein's inability to hydrolyze GTP, thus contributing to uncontrolled cell proliferation, a hallmark of cancer development. In summary, RTKs are upstream of Ras in the signaling pathway, and the activation of RTKs leads to the regulated activation of Ras and downstream effectors.