Fatty acid-binding protein

About: Fatty acid-binding protein is a research topic. Over the lifetime, 1721 publications have been published within this topic receiving 81530 citations. The topic is also known as: FABP.

Cytoplasmic transport of lipids: Role of binding proteins

Abstract: After entering the cell, small molecules must penetrate the cytoplasm before they are metabolized, excreted or can convey information to the cell nucleus. Without efficient cytoplasmic transport, most such molecules would efflux back from the cell before they could reach their targets. Conversely, intracellular lipids generated by hydrolysis of triglycerides, phospholipids and other esters must be transported away from their site of formation to prevent toxic accumulation. Intracellular movement of all molecules is slowed by molecular crowding, tortuosity, and the greater viscosity of the cytosol relative to water. However, lipids and other amphipathic molecules are further slowed by their tendency to bind to cytoplasmic membranes. Cytoplasmic binding proteins reduce membrane binding by increasing the aqueous solubility of their ligands. These aqueous carriers catalyze the transport of lipid molecules across hydrophilic water layers just as plasma membrane carriers catalyze the transport of hydrophilic molecules across the hydrophobic membrane core. They even display the principal features of carrier-mediated transport, including saturation, mutual competition, and countertransport. Higher concentrations of cytoplasmic binding proteins are associated with more rapid cytoplasmic transport of longchain fatty acids. Available data suggest that substantial intracellular concentration gradients of fatty acids should exist, and that these gradients may help determine which metabolic pathway the fatty acid enters. Thus, cytoplasmic carrier proteins may help regulate the uptake and metabolism of fatty acids and other lipid molecules.

Transport and Utilization of Lipids in Insect Flight Muscles

Abstract: In migrating lepidopteran and orthopteran insects, lipid is the preferred fuel for sustained flight activity. Diacylglycerol is delivered by lipophorin to the flight muscle and hydrolyzed to free fatty acid and glycerol. After penetrating the plasma membrane by an unknown mechanism, fatty acids are bound by the intracellular fatty acid binding protein (FABP) and transported through the cytosol. After their conversion to acyl-CoA esters, the fatty acids enter the mitochondrial matrix via the carnitine shuttle for subsequent β-oxida- tion. This article reviews the current knowledge of lipid metabolism in insect flight muscle, with particular emphasis on the structure and function of FABP and its expression during locust development and flight. comp biochem physiol 117B;4:475-482, 1997. © 1997 Elsevier Science Inc. Insects that engage in migratory flight activity usually de- to their CoA-esters that enter the β-oxidation pathway. pend on lipids as an energy source for the flight muscle. This brief description highlights both the parallels and Lipid utilization during sustained flight has been extensively differences in lipid metabolizing pathways in insects and studied in lepidopteran and orthopteran species. The pro- vertebrates. Extended activity in vertebrate red muscle is cesses involved in lipid release from the fat body and their fueled by β-oxidation of fatty acid as well. In the circulatory transport through the aqueous hemolymph have been de- system, proteins are also responsible for the transport of the scribed in detail in the reviews by Goldsworthy et al., van hydrophobic lipids, either triacylglycerol or free fatty acid. der Horst and van Marrewijk and Chino elsewhere in this Triglycerides are complexed in a large lipoprotein (very- issue. Upon stimulation by adipokinetic hormone, diacyl- low-density lipoprotein, VLDL), whereas free fatty acids are glycerol (DAG) is released from fat body into the hemo- transported by serum albumin, an abundant blood protein lymph, where it associates with the core high-density that has several high affinity and many additional low affin- lipophorin (HDLp) particle and free apolipophorin III ity binding sites for fatty acids (28). Free fatty acid is the (apoLp-III) to form a DAG-enriched low-density lipopro- only lipid that can enter the muscle cell; most muscles tein molecule. Low-density lipophorin (LDLp) delivers therefore rely on albumin to deliver the needed fatty acid, DAG to the flight muscle. DAG is hydrolyzed outside of but heart muscle in particular can also obtain its fatty acid the muscle cell, giving rise to free fatty acid, glycerol, the from the VHDL particle. To release fatty acid from the pro- DAG-depleted HDLp particle and free apoLp-III. Except tein, triacylglycerol must be first hydrolyzed by the action for the fatty acid, all these components are hydrophilic and of a membrane-bound lipoprotein lipase (for a review, see remain initially in the hemolymph. Fatty acids, however, (35)). are imported directly into the muscle cell. Once inside, the The fate of fatty acids within the muscle cell is similar hydrophobic fatty acid molecules must move through the in both insects and vertebrates. One important difference, aqueous cytosol. They are activated by coenzyme A and however, is that the metabolic activity and hence the rate

Expression of fatty acid-binding proteins in adult hippocampal neurogenic niche of postischemic monkeys

Abstract: Intracellular fatty acid (FA) chaperones known as FA-binding proteins (FABPs) are a group of molecules known to participate in cellular metabolic processes such as lipid storage, membrane synthesis, and β-oxidation or to coordinate transcriptional programs. However, their role in adult neurogenesis still remains obscure. The FABPs expressed in the central nervous system (CNS) are heart-type (FABP3), epidermal-type (FABP5), and brain-type (FABP7). These three FABPs possess a differential affinity for polyunsaturated fatty acids (PUFAs). Recently, we reported that GPR40, a receptor for free FAs and particularly for PUFAs, is expressed in the CNS of adult monkeys and upregulated after transient global brain ischemia in the hippocampal subgranular zone (SGZ), a neurogenic niche in adulthood. The SGZ showed a peak proliferation of progenitor cells and maximal expression of GPR40 during the second week after ischemia. As both FABPs and GPR40 might be closely related to the adult neurogenesis, here, we studied the expression of FABP 3, 5, and 7 in the SGZ, comparing normal and postischemic adult monkeys. Immunoblotting revealed that FABP5 and FABP7, but not FABP3, were significantly increased on day 15 after ischemia when compared with the nonischemic control. Immunohistochemistry showed that FABP5 was almost undetectable in the control SGZ but was abundant on day 15 after ischemia. FABP 3, 5, and 7 were expressed in S-100β-positive astrocytes and nestin-positive neural progenitors. However, only FABP 5 and 7 were found in bromodeoxyuridine (BrdU)-positive newly generated cells. FABPs were most frequently coexpressed with the S-100β-positive astrocytes, whereas βIII-tubulin-or polysialylated neural cell-adhesion molecule (PSA-NCAM)-positive newborn neurons in the vicinity of the astrocytes expressed none of the three FABPs. These results support a role of astrocyte- and/or neural progenitor-derived FABPs as components of the molecular machine regulating the progenitor cell niche in the adult primate brain.