| DHCR24, also known as Seladin-1, functions as 3β-hydroxysterol Δ24-reductase within the final step of the cholesterol biosynthesis pathway, converting desmosterol to cholesterol while exhibiting dual roles in lipid metabolism and oxidative stress defense as a flavin adenine dinucleotide-dependent oxidoreductase. DHCR24 localizes to the endoplasmic reticulum with a conserved reductase domain featuring catalytic histidine and tyrosine residues essential for sterol substrate binding and hydride transfer from NADPH cofactor. Acute oxidative stress triggers rapid transcriptional upregulation of DHCR24 through SREBP-mediated cholesterol sensing, elevating cellular cholesterol pools that rigidify plasma membranes and limit reactive oxygen species influx while simultaneously scavenging hydrogen peroxide via direct nucleophilic attack by conserved cysteine residues in the active site. Chronic stress exposure, conversely, downregulates DHCR24 expression, reducing p53 stabilization through enhanced ubiquitination and proteasomal degradation that attenuates DNA damage responses and promotes prosurvival shifts toward glycolysis over oxidative phosphorylation. Interaction with APP processing machinery modulates Aβ generation by altering membrane cholesterol composition that influences γ-secretase cleavage efficiency, while reductase activity integrates with Ras-ERK signaling to induce oncogene-driven senescence through ROS accumulation and p21 activation. DHCR24 maintains axonal integrity and synaptic plasticity by sustaining cholesterol supply for myelin sheath formation and neurotransmitter vesicle trafficking, with peak expression in brain regions vulnerable to neurodegeneration. Recessive mutations abolish reductase function, leading to desmosterol accumulation characteristic of desmosterolosis, while haploinsufficiency associates with Alzheimer's vulnerability through impaired amyloid clearance. |
Lane 1: 293, Lane 2: HepG2, Lane 3: K562, Lane 4: NIH/3T3
