Mechanismus der UCP-Aktivierung durch reaktive Aldehyde

Free radicals (ROS) have been implicated in aetiology of many pathological states such as metabolic, cardiovascular and inflammatory failures. Understanding ROS action mechanisms is crucial for the development of potent therapeutic strategies in the treatment of these diseases. Uncoupling proteins (UCP) are thought to be involved in ROS regulation by transporting protons through the inner mitochondrial membrane, thereby diminishing transmembrane potential. On the other side, they are proposed to be regulated by ROS. In our previous project (Po-524/3, German Research Foundation) we have shown, that reactive aldehyde, 4-hydroxy-2-nonenal (HNE), leads to the increase of UCP1 activity only if fatty acids (FA) are present. The main goal of the present project is the evaluation of mechanisms leading to FAmediated uncoupling protein activation in the presence of HNE. We will test two main hypotheses concerning the main mechanism of the proton transport mediated by HNE: (i) reactive aldehyde influences lipid membrane parameters, leading to the facilitation of fatty acid transport (e.g. membrane fluidity, dipole or surface membrane potential) or/and (ii) HNE binding to the protein leads to the transient proton channel formation due to conformational change of protein. We use two different experimental systems, bilayer lipid membranes reconstituted with uncoupling proteins and primary neuronal cell cultures, which are supposed to complement each other. We will investigate the influence of other biologically important reactive aldehydes such as malondialdehyde, 4-oxo-2-nonenal and 4-oxo-2-hexenal on the protein transport function and evaluate possible mechanisms. From the results obtained we expect to gain mechanistic insight into the controversially discussed regulation of UCP1 and UCP2 by HNE and other reactive aldehydes, which is important for drug design.

Zentrum für Biologische Wissenschaften