Isoprenylcysteine-binding pocket in G-protein effectors

Isoprenylcysteine-binding pockets are specialized hydrophobic cavities within certain proteins that recognize the lipid-modified C-terminus of G-proteins (Chandra et al., 2012). These pockets are found in effectors and chaperones such as Phosphodiesterase 6 delta (PDE6δ), Rho GDP-dissociation inhibitors (RhoGDIs), and Galectins (Zimmermann et al., 2013). The primary biological role of these pockets is to facilitate the intracellular transport, membrane localization, and signaling scaffold assembly of prenylated small GTPases, including Ras, Rho, and Rab families (UniProt O43924). In the context of oncology, the PDE6δ pocket is a critical target because it chaperones farnesylated KRAS to the plasma membrane, where it drives cell proliferation (Zimmermann et al., 2013). Small molecule inhibitors like Deltarasin bind to these pockets, effectively displacing the G-protein and preventing its membrane association, which leads to the inhibition of downstream signaling pathways like MAPK/ERK (Papke et al., 2016). This approach offers a therapeutic window for treating KRAS-mutant cancers that have historically been difficult to target directly. Beyond cancer, these pockets are involved in various signaling cascades that regulate cell polarity and vesicular transport. Therapeutic development focuses on high-affinity ligands that can selectively block these pockets without affecting the broader lipid metabolism of the cell.

Other names

Prenyl-binding pocketFarnesyl-binding pocketGeranylgeranyl-binding pocketPDE6D hydrophobic pocketIsoprenyl-binding site

Competitive inhibition of the interaction between the isoprenylated (farnesylated or geranylgeranylated) C-terminus of small GTPases and the hydrophobic binding pocket of chaperone or effector proteins, such as PDE6δ (Zimmermann et al., 2013). This displacement prevents the proper intracellular trafficking and membrane localization of the G-protein, thereby attenuating its ability to engage downstream signaling effectors (Papke et al., 2016).