Exposure of HL-60 human leukaemic cells to 4-hydroxynonenal promotes the formation of adduct(s) with alpha-enolase devoid of plasminogen binding activity

HNE (4-hydroxynonenal), the major product of lipoperoxidation, easily reacts with proteins through adduct formation between its three main functional groups and lysyl, histidyl and cysteinyl residues of proteins. HNE is considered to be an ultimatemediator of toxic effects elicited by oxidative stress. It can be detected in several patho-physiological conditions, in which it affects cellular processes by addition to functional proteins. We demonstrated in the present study, by MS and confirmed by immunoblotting experiments, the formation of HNE–α enolase adduct(s) in HL-60 human leukaemic cells. α-Enolase is a multifunctional protein that acts as a glycolytic enzyme, transcription factor [MBP-1 (c-myc binding protein-1)] and plasminogen receptor. HNE did not affect α-enolase enzymatic activity, expression or intracellular localization, and did not change the expression and localization ofMBP-1 either. Confocal and electronicmicroscopy results confirmed the plasma membrane, cytosolic and nuclear localization of α-enolase in HL-60 cells and demonstrated that HNE was colocalized with α-enolase at the surface of cells early after its addition. HNE caused a dose- and time-dependent reduction of the binding of plasminogen to α-enolase. As a consequence, HNE reduced adhesion of HL-60 cells to HUVECs (human umbilical vein endothelial cells). These results could suggest a new role for HNE in the control of tumour growth and invasion.