Protacs: Chimeric molecules that target proteins to the Skp1–Cullin–F box complex for ubiquitination and degradation

TLDR

Ubiquitin-dependent proteolysis regulates intracellular protein levels, with the Skp1–Cullin–F-box (SCF) complex being a key ubiquitin ligase. The study aimed to engineer a system that directs a target protein to the SCF complex for ubiquitination and degradation. They designed Protac‑1, a chimeric molecule linking an IκBα phosphopeptide (recognized by β‑TRCP) to ovalicin, thereby recruiting MetAP‑2 to the SCF complex. Protac‑1 successfully tethered MetAP‑2 to SCF β‑TRCP, leading to its ubiquitination and degradation, demonstrating a proof‑of‑concept for conditional protein inactivation and therapeutic targeting.

Abstract

The intracellular levels of many proteins are regulated by ubiquitin-dependent proteolysis. One of the best-characterized enzymes that catalyzes the attachment of ubiquitin to proteins is a ubiquitin ligase complex, Skp1-Cullin-F box complex containing Hrt1 (SCF). We sought to artificially target a protein to the SCF complex for ubiquitination and degradation. To this end, we tested methionine aminopeptidase-2 (MetAP-2), which covalently binds the angiogenesis inhibitor ovalicin. A chimeric compound, protein-targeting chimeric molecule 1 (Protac-1), was synthesized to recruit MetAP-2 to SCF. One domain of Protac-1 contains the IκBα phosphopeptide that is recognized by the F-box protein β-TRCP, whereas the other domain is composed of ovalicin. We show that MetAP-2 can be tethered to SCF β -TRCP , ubiquitinated, and degraded in a Protac-1-dependent manner. In the future, this approach may be useful for conditional inactivation of proteins, and for targeting disease-causing proteins for destruction.