Beyond the Identification of Transcribed
Functional and Expression Analysis
11th Annual Workshop
November 9-12, 2001
Department of Biochemistry and Molecular Biology
University of Debrecen, Medical and Health Science Center
98 Nagyerdei krt.
presenter: Laszlo Nagy
Laszlo Nagy, Attila Szanto and Istvan Szatmari
Department of Biochemistry and Molecular Biology, University of Debrecen, Nagyerdei krt. 98, DEBRECEN, Hungary H-4012
Nuclear hormone receptor are ligand activated transcription factors. We are trying to understand how these receptors modulate cellular differentiation and function and what is their contribution to diseases such as atherosclerosis and immune response. Since the receptors transcriptional activity can be regulated (switched on) by small lipid soluble molecules they are excellent targets of global expression profiling.
We have been using real time quantitative PCR for absolute transcript number determination and DNA microarrays for global transcription profiling to determine receptor levels, target genes profiles and to identify components of the genetic programs of receptor activation
A group of receptors such as PPARs (Peroxisome Proliferator Activated Receptor) and LXR (Liver X Receptor) can be activated by modified fatty acids and cholesterol molecules, respectively. Using natural and synthetic ligands we have characterized the role of these receptors in myeloid cell differentiation, lipid metabolism and dendritic cell differentiation.
We have found that oxidatively modified LDL (Low Density Lipoprotein) induces and activates PPARg in monocytes leading to macrophage differentiation, expression of the scavenger receptor CD36 and increased lipid uptake. This process operates as a positive feed back loop and contributes to foam cell formation. PPARg also increases lipid efflux from macrophages through induction of LXRa, a receptor activated by oxysterols. This leads to the increased expression of the transporter ABC1 (ATP Binding Cassette) and cholesterol efflux from macrophages. Our results suggest the existence of a transcriptional cascade and a complex and complementary role for PPARg and LXRa as key regulators of a coordinated cellular responses to oxidatively modified LDL in macrophages. Recently, we have also found that key components of this cascade also exist in maturing/differentiating antigen presenting cells (dendritic cells) of myeloid origin. The role of these transcriptional networks in normal cell function and diseases and their potential for therapeutic utilization will be discussed.