Lipid-derived electrophiles induce covalent modification and aggregation of Cu,Zn-superoxide dismutase in a hydrophobicity-dependent manner

Abstract

Lipid peroxidation generates a huge number of reactive electrophilic aldehyde products.These reactive aldehydes can modify macromolecules such as proteins, resulting in loss of function and/or aggregation. The accumulation of Cu,Zn-superoxide dismutase (SOD1) aggregates is associated with familial cases of amyotrophic lateral sclerosis (ALS). Recent studies have shown that lipid and its oxidized derivatives may play a role in this process. Here we aimed to compare and characterize the ability of lipid-derived electrophiles with different hydrophobicities to induce SOD1 modification and aggregation in vitro. SOD1 was incubated with 4-hydroxy-2-hexenal (HHE), 4-hydroxy-2-nonenal (HNE), 2-hexen-1-al (HEX), 2,4-nonadienal (NON), 2,4-decadienal (DEC) or secosterol aldehydes (Seco-A or Seco-B) at 37°C for 24 h. Size exclusion chromatography analysis showed that hydrophobic aldehydes markedly enhances apo-SOD1 aggregation. More importantly, aggregation level was positively correlated to calculated aldehyde hydrophobicities (LogP). Protein sequencing by LC-MS/MS showed that aldehydes covalently modifies SOD1 at aggregation prone regions. For instance, specific lysine residues located mainly nearby the dimer interface (K3, K9) and at the electrostatic loop (K122, K128, K136) were ubiquitously modified by all aldehydes. The a,b-unsaturated aldehydes also promoted modifications on histidine and cysteine residues, with H120 and C6 being the most commonly modified residues. Overall, our data suggest that electrophile`s hydrophobicity is a critical factor that strongly influences protein aggregation propensity.

Activation of the Nrf2 Pathway as a Therapeutic Strategy for ALS Treatment

“…In addition, the GSSG/GSH ratio, another indicator of OS, has been reported to be increased in ALS mouse models [ 29 ] and ALS patients [ 18 , 20 ]. Interestingly, lipid peroxidation has been shown to promote superoxide dismutase 1 (SOD1) aggregation, which is involved in some familial forms of ALS and could contribute to the pathology [ 30 ].…”