Study On DhHP-6’s Structural Characterization And The Mechanisms Of Extending Lifespan In Caenorhabditis Elegans

DhHP-6is composed of a deuterohemin prosthetic group bonded to six aminoacid residues (β-AlaHisThrValGluLys). A key feature in the active-site structure ofheme proteins is the presence of a basic amino acid side chain axially ligated to theiron center of the cofactor, on the side opposite to which the catalytic reaction occurs.The effect of strain in the axial coordination of imidazole to the deuteroheme has beenstudied in the chelate complexes DhHP-6, DhAP-6and PoHP-6. The spectral, bindingand catalytic properties of DhHP-6are significantly different from those of DhAP-6and PoHP-6. These differences are determined by some local structural changesaround the deuteroheme which are generated by binding properties of axial imidazolechelated deuterohemin complexes. The bonding interaction between the axialimidazoleand the iron(III) center in strained chelated deuterohemin complexes ofDhHP-6increase both the affinity for a fifth axial ligand catalytic activity of thecomplex in the peroxidative reaction. So only DhHP-6could efficiently catalyzesubstrate oxidations using hydrogen peroxide (H2O2) as a peroxidases.Previous studies have demonstrated that DhHP-6provides longevity and increasesstress resistance in Caenorhabditis elegans. SIR-2.1gene and transcription factorabnormal Dauer formation (DAF-16) play critical roles in determining C. eleganslifespan. DhHP-6was speculated to reduce the ROS level and extend the lifespan of C.elegans via SIR-2.1-and DAF-16-mediated signaling pathway. We defined the rolesof SIR2.1gene and DAF-16in longevity and the effects of DhHP-6on DAF-16activation using WT, DAF-16mutant, DAF-16::GFP, and SOD-3::GFP strains andRNAi for SIR-2.1and L4440. Niacin Amide (NAM) or SIR-2.1RNAi blocked thelongevity effect of DhHP-6via SIR2.1pathway inhibition. DhHP-6did not extend the lifespan of the DAF-16mutant C. elegans. Further studies demonstrated thatDhHP-6induces nuclear translocalization and activation of DAF-16. Nucleartranslocalization of DAF-16was not mediated by SIR-2.1, while the activation ofDAF-16depends on SIR-2.1expression. Results suggest that DhHP-6extends thelifespan of C. elegans via SIR2.1and DAF-16pathway, and that DhHP-6triggersDAF-16nuclear translocalization and activation. Our findings provide novel insighton the longevity effect of DhHP-6.