Cellular lipid binding proteins: expression, function, and nutritional regulation ¹

Abstract

The membrane transport and cytosolic solubilization of hydrophobic ligands, including sterols, fatty acids, retinoids, and certain hydrophobic carcinogens, are facilitated by a group of similar low molecular weight proteins: plasma membrane transport protein, fatty acid binding proteins, sterol carrier protein, and retinoid binding proteins. The cellular content of these proteins, which establishes the capacity of a cell to utilize the various ligands, is determined by events regulating transcription and translation, e.g., the mRNA abundance of liver- and gut-type FABPs is increased by dietary fat, and translation of hepatic FABP appears to be stimulated by insulin. Functions attributable to these lipid binding proteins remain unclear, but data are presented that indicate physiological roles in 1) fatty acid transport, esterification, and oxidation, 2) steroidogenesis, and 3) retinoid uptake, retinaldehyde reduction, and retinol esterification. An exciting and novel prospect for cellular trafficking proteins is the role they may play in regulating gene expression. In this respect, cellular lipid binding proteins, e.g., retinoid binding proteins, may deliver their ligands to nuclear trans-acting proteins, and thereby modulate genes coding for key proteins involved in lipid metabolism or differentiation. Even though the functions of these proteins still need to be unequivocally established, it is clear that they are important in the overall homeostasis of lipid metabolism.

Gene Expression Profiling in Daphnia magna Part I: Concentration-Dependent Profiles Provide Support for the No Observed Transcriptional Effect Level

“…The downregulation of two of these genes, cellulase and preamylase, was confirmed by q-RT-PCR (see Table S4 in the Supporting Information). Genes involved in other areas of digestion were downregulated by metal exposure including trypsin, whose primary function is in protein digestion, and fatty-acid binding proteins, whose expression is linked to lipid intake in other animals (14). There are several possible mechanisms that could explain the decreased expression of these three classes of related genes.…”

cDNA Cloning and Characterization of a cis-Retinol/3α-Hydroxysterol Short-chain Dehydrogenase

“…2 These observations indicate that SDRs have considerable roles in retinoid metabolism, just as they have in steroid hormone metabolism. Thus, steroids and retinoids seem to share families of metabolic enzymes, ligandactivated receptors (2,3,6), and cellular binding-proteins (46,47).…”

Intracellular Lipid-Binding Proteins and Their Genes

“…In contrast, a high-fat meal results in a nearly twofold increase in liver FABP and intestinal FABP (4,81). In cell culture systems, free fatty acids upregulate liver FABP expression (19). In addition, long-chain fatty acids rapidly induce the expression of adipocyte LBP in a variety of preadipocyte cell lines (24).…”