CYTOPLASMIC FATTY-ACID BINDING-PROTEIN - SIGNIFICANCE FOR INTRACELLULAR-TRANSPORT OF FATTY-ACIDS AND PUTATIVE ROLE ON SIGNAL TRANSDUCTION PATHWAYS

The cellular transport of long-chain fatty acid moieties is thought to be mediated by a plasmalemmal and a cytoplasmic fatty acid binding protein (FABP(PM) and FABP(C), respectively) and a cytoplasmic acyl-coenzyme A binding protein (ACBP). Their putative main physiological significance is the assurance that long-chain fatty acids and derivatives, either in transit through membranes or present in intracellular compartments, are largely complexed to proteins. FABP(C) distinguishes from the other proteins in that distinct types of FABP(C) exist and that these are found in a variety of tissues in remarkable abundance, with some cells containing more than one type in addition, liver type FABP(C) binds not only fatty acids, but also several other hydrophobic ligands, including heme, bilirubin, prostaglandin E1 and lipoxygenase metabolites of arachidonic acid. Calculations made for rat cardiomyocytes reveal that the presence of FABP(C) substantially enhances the cytoplasmic solubility as well as the maximal diffusional flux of fatty acids in these cells. Apart from this putative function in the bulk transport of ligands, FABP(C) may also function in the fine-tuning of cellular events by modulating the metabolism of hydrophobic compounds implicated in the regulation of cell growth and differentiation.