8.A.33 The Fatty Acid Binding Protein (FABP) Family
The fatty acid-binding protein (FABP) plays an important role in uptake of long-chain fatty acids (LCFA) and energy metabolism by eukaryotic cells. Infection of liver cells with chlamydial organisms promotes fatty acid uptake by the infected cells, suggesting that LCFA may benefit chlamydial growth. Introduction of FABP into the liver cells not only enhanced fatty acid uptake, but also increased chlamydial intravacuolar replication and maturation. The FABP-enhanced chlamydial intracellular growth was dependent on the host cell uptake of fatty acids. These results demonstrated that C. trachomatis can productively infect liver cells and utilize FABP-transported LCFA for its own biosynthesis (Wang et al., 2007).
Cytosolic FABP or lipocalin is ~130aas long with two hydrophobic peaks that could bind fatty acids and/or interact with membranes. The 3d-structure has been determined by X-ray crystalography and NMR. The protein binds stearic acid with highest affinity. Affinity decreases with decreasing chain length or introduction of unsaturation (Sugenthaler et al., 1994). FABP may function in keratinocyte differentiation.
The endocannabinoids (anandamide, AEA, and 2-arachidonoyl glycerol, 2-AG) are non-charged lipids that readily cross lipid membranes, but are water immiscible. The FABPs act as carriers to solubilize and transport endocannabinoids through the aqueous cytoplasm. The FABPs that function in this capacity include FABP1, FABP3, FABP5 and FABP7 (Murillo-Rodriguez et al. 2017).