2 research outputs found
Molecular Structures of Isolevuglandin-Protein Cross-Links
Isolevuglandins (isoLGs) are stereo
and structurally isomeric γ-ketoaldehydes
produced through free radical-induced oxidation of arachidonates.
Some isoLG isomers are also generated through enzymatic cyclooxygenation.
Post-translational modification of proteins by isoLGs is associated
with loss-of-function, cross-linking and aggregation. We now report
that a low level of modification by one or two molecules of isoLG
has a profound effect on the activity of a multi subunit protease,
calpain-1. Modification of one or two key lysyl residues apparently
suffices to abolish catalytic activity. Covalent modification of calpain-1
led to intersubunit cross-linking. Hetero- and homo-oligomers of the
catalytic and regulatory subunits of calpain-1 were detected by SDS–PAGE
with Western blotting. <i>N</i>-Acetyl-glycyl-lysine methyl
ester and β-amyloid(11–17) peptide EVHHQKL were used
as models for characterizing the cross-linking of protein lysyl residues
resulting from adduction of iso[4]ÂLGE<sub>2</sub>. Aminal, bispyrrole,
and trispyrrole cross-links of these two peptides were identified
and fully characterized by mass spectrometry. Aminal and bispyrrole
dimers were both detected. Furthermore, a complex mixture of derivatives
of the bispyrrole cross-link containing one or more additional atoms
of oxygen was found. Interesting differences are evident in the predominant
cross-link type generated in the reaction of iso[4]ÂLGE<sub>2</sub> with these peptides. More aminal cross-links versus bispyrrole are
formed during the reaction of the dipeptide with iso[4]ÂLGE<sub>2</sub>. In contrast, more bispyrrole versus aminal cross-links are formed
during the reaction of EVHHQKL with iso[4]ÂLGE<sub>2</sub>. It is tempting
to speculate that the EVHHQKL peptide–pyrrole modification
forms noncovalent aggregates that favor the production of covalent
bispyrrole cross-links because β-amyloid(11–17) tends
to spontaneously oligomerize
Detection and Biological Activities of Carboxyethylpyrrole Ethanolamine Phospholipids (CEP-EPs)
Oxidation of docosahexaenoate phospholipids
produces 4-hydroxy-7-oxo-hept-5-eonyl
phospholipids (HOHA-PLs) that react with protein lysyl ε-amino
residues to generate 2-ω-carboxyethylpyrrole (CEP) derivatives,
endogenous factors that induce angiogenesis in the retina and tumors.
It seemed likely, but remained unproven, that HOHA-PLs react with
ethanolamine phospholipids (EPs) <i>in vivo</i> to generate
CEP-EPs. We now show that CEP-EPs are present in human blood at 4.6-fold
higher levels in age-related macular degeneration plasma than in normal
plasma. We also show that CEP-EPs are pro-angiogenic, inducing tube
formation by human umbilical vein endothelial cells by activating
Toll-like receptor 2. CEP-EP levels may be a useful biomarker for
clinical assessment of AMD risk and CEP-associated tumor progression
and a tool for monitoring the efficacy of therapeutic interventions