CRL3mediated

CRL3-mediated refers to protein ubiquitination carried out by Cullin-3–based E3 ubiquitin ligase complexes. These are modular enzymes composed of a Cul3 scaffold, a RING finger protein (RBX1), an E2 conjugating enzyme, and a set of substrate receptors that determine which proteins are targeted for ubiquitination. The entire complex is regulated by post-translational modifications and by the availability of substrate receptors, enabling selective control over substrate turnover.

Substrate receptors are typically BTB-domain–containing proteins, including KEAP1, KLHL family members, and SPOP. KEAP1 recruits NRF2 to CRL3 for ubiquitination under normal conditions, restricting NRF2 activity; upon oxidative stress, NRF2 is stabilized and activates protective gene expression. Other receptors regulate diverse substrates: KLHL3 targets WNK kinases, influencing ion transport and blood pressure; KLHL12 participates in turnover of Dishevelled in Wnt signaling; SPOP targets various transcriptional regulators and coactivators, with implications in cancer when mutated.

Regulation of CRL3 activity involves neddylation of Cul3, which enhances ligase activity, and deneddylation by the COP9 signalosome, which resets the complex. The dynamics of substrate receptor expression and turnover, as well as phosphorylation of substrates, can modulate substrate recognition. Pharmacological inhibition of NEDD8 activation (for example, pevonedistat) blocks CRL function and is being explored in cancer therapy.

Biological significance: CRL3-mediated ubiquitination controls development, stress responses, metabolism, and signaling pathways. Dysregulation of CRL3, especially the KEAP1–NRF2 axis, is linked to cancer and chemoresistance. Ongoing research continues to identify additional BTB-domain receptors and substrates, expanding understanding of proteostasis and cellular signaling networks.