Question

In certain cancers, the GTPase activity of the RAS G-protein is inhibited. This means that the RAS protein can no longer hydrolyze GTP into GDP. What effect would this have on downstream cellular events?

Short answer

As a downstream cellular event malignancy will be more prominent.

Step-by-step solution

Introduction

In RAS signalling pathway Binding of epidermal growth factor (EGF) to EGF receptor activates SOS that binds RAS with GTP. Then RAF is activated that later again activates MEK ,which phosphorylates ERK. ERK phosphorylates various substrates that help in cell proliferation, growth, migration and differentiaton. RAS proteins are controlled by its GTPase activity. When it is bound to GTP it becomes active and if GTP is hydrolyzed to GDP , then the switch is turned 'off' (inactive form). So, , if the GTPase activity of the RAS G-protein is inhibited , it will become permanently active.

Explanation

The Extracellular-signal-regulated kinase (ERK) pathway will be permanently activated if the RAS switch is permanently turned 'on'. As a result, there will be increased cell proliferation, migration, adhesion, differentiation and angiogenesis. Apoptosis will also be inhibited and it may lead to tumerogenesis.