出版社:American Society for Biochemistry and Molecular Biology
摘要:Electronegative low density lipoprotein (LDL–) formation that structurally resembles LDL– isolated from plasma was evaluated after LDL treatment with snake venom phospholipase A2 (PLA2). PLA2 treatment of LDL increased its electrophoretic mobility in proportion to the amount of LDL– formed without evidence of lipid peroxidation. These changes dose-dependently correlated with the degree of phospholipid hydrolysis. Strong immunoreactivity of LDL– subfraction from plasma and PLA2-treated LDL (PLA2-LDL) to amyloid oligomer-specific antibody was observed. Higher ß-strand structural content and unfolding proportionate to the loss of -helical structure of apolipoprotein B-100 (apoB-100) of LDL– isolated from both native and PLA2-LDLs was demonstrated by circular dichroism (CD) spectropolarimetry. These structural changes resembled the characteristics of some oxidatively modified LDLs and soluble oligomeric aggregates of amyloidogenic proteins. PLA2-LDL was also more susceptible to nitration by peroxynitrite, likely because of exposure of otherwise inaccessible hydrophilic and hydrophobic domains arising from apoB-100 unfolding. This was also demonstrated for plasma LDL–. In contrast, PLA2-LDL was more resistant to copper-mediated oxidation that was reversed upon the addition of small amounts of unsaturated fatty acids.
The observed similarities between PLA2-LDL–-derived LDL– and plasma LDL– implicate a role for secretory PLA2 in producing modified LDL– that is facilitated by unfolding of apoB-100.
Abbreviations: Aß, amyloid ß; apoB-100, apolipoprotein B-100; CD, circular dichroism; LDL–, electronegative low density lipoprotein; MDA, malondialdehyde; nLDL, normal LDL subfraction devoid of LDL–; REM, relative electrophoretic mobility; sPLA2, secretory phospholipase A2; tLDL, total LDL