title: Protein-protein interaction heterogeneity of plasma apolipoprotein A1 in nephrotic syndrome.
abstract: Apolipoprotein A1 (apoA1) is a component of the high density lipoproteins (HDL) that regulates the transport of cholesterol between the liver and peripheral cells and modulates the removal of any excess of cholesterol from membranes. Any variation in apoA1 composition may modify the plasma lipid profile and be involved in atherogenesis. We investigated apoA1 composition in plasma of 6 children with nephrotic syndrome, a condition characterized by high levels of cholesterol in plasma and by a high risk to develop atherosclerosis. Non-denaturing two-dimensional electrophoresis (Nat/SDS-PAGE), mass spectrometry, western blot and pull down experiments were done to characterize proteins and define putative interactions. ApoA1 was resolved in 12 variants, 6 of which had a slightly lower molecular weight (18-19 KDa) and migrated on the same axes of the β chain of haptoglobin (Hp). Low molecular weight apoA1 were observed in carriers of different Hp haplotypes (including one homozygous for the rare ββα1α1) ruling out any contaminant effect of co-migration of apoA1 with Hp α2 chain. Overall, apoA1 isoforms were much more present in plasma of nephrotic patients compared to a normal profile. These findings show that apoA1 plasma in nephrotic syndrome is heterogeneous in terms of molecular weight. Low molecular weight fragments lack internal structural domains and likely form macro-aggregates with Hp. Fragmentation and transport of apoA1 may be involved in the general disorder of lipid metabolism that characterizes nephrotic syndrome.
authors.affiliation: Divisione di Nefrologia e Laboratorio di Fisiopatologia dell'Uremia, G. Gaslini Children's Hospital, Genova, Italia.
authors.forename: Laura
authors.initials: L
authors.lastname: Santucci
authors.forename: Giovanni
authors.initials: G
authors.lastname: Candiano
authors.forename: Andrea
authors.initials: A
authors.lastname: Petretto
authors.forename: Barbara
authors.initials: B
authors.lastname: Pavone
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bruschi
authors.forename: Rosanna
authors.initials: R
authors.lastname: Gusmano
authors.forename: Giorgio
authors.initials: G
authors.lastname: Federici
authors.forename: Andrea
authors.initials: A
authors.lastname: Urbani
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Ghiggeri
mesh_terms: D000293:Adolescent; D000328:Adult; D016632:Apolipoprotein A-I / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D015153:Blotting, Western; D002648:Child; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D009404:Nephrotic Syndrome / Q000097:blood*; D011485:Protein Binding; D055815:Young Adult
chemical_list: D016632:Apolipoprotein A-I