KEAP1 (kelch like ECH associated protein 1; HGNC:23177, NCBI Gene ID 9817) is a human locus mapped to chromosome band 19p13.2 that encodes homodimeric cytosolic BTB-Kelch substrate adaptor & cysteine redox sensor KEAP1 (624 aa; 70 kDa). KEAP1 acts in basal Cullin-3 (CUL3) ubiquitylation of NFE2L2 (NRF2) vs. Cys151/Cys273/Cys288 electrophilic modification unleashing NRF2, together with NFE2L2 / NRF2 (Master Antioxidant Transcription Factor Regulated by KEAP1), Glutathione Antioxidant Pathway, and Actin Cytoskeleton (Anchors Cytosolic KEAP1). Encodes the cysteine-rich cytosolic redox sensor and Cullin-3 E3 ubiquitin ligase adaptor KEAP1 that gates NRF2 antioxidant signaling.
Basal Cullin-3 (CUL3) ubiquitylation of NFE2L2 (NRF2) vs. Cys151/Cys273/Cys288 electrophilic modification unleashing NRF2
Clinical / Therapeutic Role
Direct covalent target of dimethyl fumarate, omaveloxolone & sulforaphane; somatically inactivated in ~20% of non-small-cell lung cancers
Gene Structure & Expression
Genomic Organization & Cytogenetic Locus: 6-exon gene on chromosome 19p13.2 encoding a 624-amino-acid polypeptide containing 27 highly reactive cysteine residues distributed across three functional domains: an N-terminal Broad-Complex, Tramtrack, and Bric-a-Brac (BTB) homodimerization and CUL3-binding domain (containing the primary electrophile sensor Cys151), a central Intervening Region (IVR, containing stress sensors Cys273 and Cys288), and a C-terminal six-bladed beta-propeller Double-Glycine Repeat / Kelch domain.
Cellular & Tissue Expression Profile: Ubiquitously expressed in the cytoplasm (tethered to the perinuclear actin cytoskeleton) of all human epithelial, endothelial, metabolic, and neural cells.
Molecular Function & Pathways
Biochemical & Physiological Mechanism: Operates via a "hinge-and-latch" conformational cycle: one homodimer of KEAP1 uses its two C-terminal Kelch beta-propeller domes to simultaneously grab the high-affinity ETGE motif ("hinge") and low-affinity DLG motif ("latch") within the Neh2 domain of a single NFE2L2 (NRF2) molecule, positioning seven lysine residues between them for polyubiquitylation by the CUL3-RBX1 E3 ligase; when oxidative stress, endogenous fumarate/itaconate, or electrophilic drugs alkylate Cys151 (or Cys226/613/622/624 for H2O2 and Cys273/288 for alkenals), KEAP1 changes conformation so NRF2 cannot be ubiquitylated or released—saturating existing KEAP1 dimers and allowing newly translated NRF2 to enter the nucleus; selective autophagy adaptor p62 (SQSTM1, phosphorylated at Ser349) also competitively displaces the NRF2 DLG latch to target KEAP1 for autophagic degradation.
Clinical & Therapeutic Significance
Human Genetic Variants & Disease Phenotypes: Homozygous Keap1 knockout in mice causes lethal postnatal hyperkeratosis of the esophagus and forestomach due to constitutive unchecked Nrf2 activity (completely rescued by simultaneous Nfe2l2 deletion); in human lung adenocarcinoma and squamous cell carcinoma, somatic loss-of-function mutations in KEAP1 are among the top driver events promoting metabolic reprogramming and resistance to ferroptosis and immunotherapy.
Therapeutic & Clinical Pharmacology: Cys151 in the BTB domain of KEAP1 is the direct covalent target of FDA-approved omaveloxolone (Skyclarys) and dimethyl fumarate (Tecfidera), while non-covalent small molecules and cyclic peptides that competitively occupy the C-terminal Kelch beta-propeller dome to displace the NRF2 ETGE/DLG motifs are in clinical development for chronic kidney disease, pulmonary inflammation, and neurodegeneration.