Fibroblast growth factor receptors (FGFRs) are transmembrane proteins that regulate cellular processes such as cell proliferation and differentiation. The extracellular domains of FGFR proteins bind specifically to signaling molecules called fibroblast growth factors. The intracellular domains of FGFR proteins function as protein kinases, enzymes that transfer phosphate groups from ATP to protein substrates.
FGFR activation occurs when binding by fibroblast growth factors causes FGFR proteins in the plasma membrane to become closely associated with each other. The association of two FGFR proteins stimulates protein kinase activity, which triggers the activation of intracellular signaling pathways.
A simplified model of FGFR activation is represented in Figure 1.
Which of the following changes in the FGFR signaling pathway is most likely to result in uncontrolled cell proliferation?
answer choices
The irreversible association of FGFR proteins
The loss of the FGFR protein kinase function
A decrease in the intracellular concentration of ATP
A decrease in the extracellular concentrations of fibroblast growth factors
