Elucidating the mechanism of transendothelial fatty acid transport

• Applicant: Professor Dr. Joachim Füllekrug
• Subject Area: Cell Biology ; Biochemistry
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389324783

Fatty acids and the lipids made from them are essential components of every cellular form of life. Exogenous fatty acids are taken up by transport across the plasma membrane, and this is usually followed very soon by their esterification with coenzyme A. This "activation" of fatty acids is indispensable for their further metabolism. In our published preliminary work we have characterized several membrane proteins involved in cellular fatty acid uptake, especially putative transporter proteins (FATPs and CD36) and fatty acyl-CoA ligases. Now we would like to use the developed molecular tools thereby to address the most urgent open questions in this still very controversial field of research, in particular the relationship between fatty acid transport and metabolism. The model system is going to be peripheral microvascular endothelial cells which are distinguished by a high capacity for fatty acid uptake and transport.The overall key question of this proposal is: Which is the molecular mechanism for the favored transport of fatty acids across the endothelium as opposed to their metabolism by the endothelial cells? Driving forces for the transport of fatty acids are in principle: regulation by fatty acid transport proteins, concentration differences between luminal and abluminal endothelial plasma membrane, higher velocity of transport as compared to metabolism, and the protection of non-esterified fatty acids against the cytosolically oriented CoA ligases. These hypotheses will be examined by the work program, and correlated to each other. The expression level of the candidate proteins is going to be modified by retrovirus mediated RNA interference or overexpression respectively. Immortalized as well as primary cultures of endothelial cells will be differentiated on permeable filters to be able to measure fatty acid transport and metabolism simultaneously. The focused project aims derived from the hypotheses are:1. Elucidation of the mechanism of action of the FATP transporters.2. Identification of the underlying dominant determinants for the high velocity of fatty acid transport as compared to endothelial metabolism.3. Investigation if cytosolic proteins or caveolae protect non-esterified fatty acids from the metabolic enzymes.Summarizing, endothelial cells are a unique model system which are excellently suited to answer basic and important questions regarding cellular fatty acid transport. We assume that our results will also be relevant for the transport across the blood brain barrier as well as for the understanding of widespread lipid associated metabolic diseases.

• DFG Programme: Research Grants