FABP1

Last updated
FABP1
Protein FABP1 PDB 2f73.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases FABP1 , FABPL, L-FABP, fatty acid binding protein 1
External IDs OMIM: 134650 MGI: 95479 HomoloGene: 1106 GeneCards: FABP1
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001443

NM_017399

RefSeq (protein)

NP_001434

NP_059095

Location (UCSC) Chr 2: 88.12 – 88.13 Mb Chr 6: 71.18 – 71.18 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

FABP1 is a human gene coding for the protein product FABP1 (Fatty Acid-Binding Protein 1). It is also frequently known as liver-type fatty acid-binding protein (LFABP).

FABP1 is primarily expressed in the liver where it is involved in the binding, transport and metabolism of long-chain fatty acids (LCFAs), endocannabinoids, phytocannabinoids (and less so for synthetic cannabinoid receptor (CBR) agonists and antagonists) and other hydrophobic molecules. [5] [6] [7] [8] Altered expression of the protein has been linked to metabolic conditions including obesity. [9]

Discovery

The fatty acid-binding proteins (FABPs) were initially discovered in 1972 with experiments using 14C labelled oleate to identify the presence of a soluble fatty acid carrier in the enterocyte responsible for intestinal absorption of (LCFAs). [10] Since then, ten members of the FABP family have been identified on the human genome. Nine are well established (FABP1-9) with a recently discovered tenth (FABP12). [7] Each FABP corresponds to particular organs/tissue around the body where they play a role in fatty-acid uptake, transport and metabolism. [10]

Gene location

The human FABP1 gene is located on the short (p) arm of chromosome 2 from base pair 88,122,982 to base pair 88,128,131. [11]

Protein structure

FABP1 has been found to have a unique structure compared to other members of the FABP family, allowing it to bind multiple ligands simultaneously. [12] It also has a larger solvent-accessible core compared to other FABPs allowing more diverse substrate binding. [7] The “portal hypothesis” has been proposed to explain the binding process of FABPs. [7] It has been suggested that fatty acids enter the solvent-accessible area of the protein through a dynamic region consisting of α-helix II and turns between βC-βD and βE-βF loops. [13] The fatty acid is then bound in the protein cavity for transport. [13]

Function

The FABPs are a family of small, highly conserved cytoplasmic proteins involved in the binding of LCFAs. FABP1 is expressed abundantly in the human liver where it accounts for 7-11% of the total cytosolic protein, and can also be found in the intestine, kidney, pancreas stomach and lung. [7] [14] FABP1 is unique in the wider range of other hydrophobic ligands it can bind including bilirubin, monoglycerides, bile acids and fatty acyl CoA. [15] [16] [17] [18] It has been proposed that FABP1 plays a significant role in preventing cytotoxicity by binding heme, fatty acids and other molecules that are potentially toxic when unbound. [12]

Mutations

On exon 3 of the human FABP1 gene an Thr to Ala substitution has been identified leading to a T94A missense mutation. [19] Carriers of this particular single nucleotide polymorphism (SNP) exhibit higher baseline plasma-free fatty acid levels, lower BMI and a smaller waist circumference. [19] The T94A mutant has also been associated with metabolic syndrome conditions, cardiovascular disease and T2DM. [19]

Protein expression

Suppression

Studies with mice to determine the effect of suppressing the FABP1 gene have been performed. When provided with high-fat or high-cholesterol based diets those with suppressed FABP1 expression demonstrated a significant impact on metabolic regulation and weight gain. [20] [21] [22] [23]

Increased levels in obesity

A study in Chinese young adults indicates a strong relationship between serum FABP1 levels and lipid profile, body measurements and homeostatic parameters. [9] Increased BMI and insulin resistance in subjects demonstrated higher serum FABP1 with a particular correlation in subjects with central adiposity. [9] This elevation is suggested to occur as a compensatory up-regulation of the protein in an attempt to counter the high metabolic stress associated with obesity. Alternately obesity may in fact lead the human body to develop resistance to the actions of FABP1 leading to the compensatory up-regulation. [9]

Disease marker

Evaluation of increased levels of urinary and serum FABP1 have also shown to be effective markers in the detection of intestinal ischaemia, progressive end-stage renal failure and ischaemic damage caused by renal transplantation or cardiac bypass surgery. [24] [25] [26]

Related Research Articles

<span class="mw-page-title-main">Anandamide</span> Chemical compound (fatty acid neurotransmitter)

Anandamide (ANA), also known as N-arachidonoylethanolamine (AEA), an N-acylethanolamine (NAE), is a fatty acid neurotransmitter. Anandamide was the first endocannabinoid to be discovered: it participates in the body's endocannabinoid system by binding to cannabinoid receptors, the same receptors that the psychoactive compound THC in cannabis acts on. Anandamide is found in nearly all tissues in a wide range of animals. Anandamide has also been found in plants, including small amounts in chocolate. The name 'anandamide' is taken from the Sanskrit word ananda, which means "joy, bliss, delight", plus amide.

<span class="mw-page-title-main">Cannabinoid receptor</span> Group of receptors to cannabinoid compounds

Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system of vertebrates– a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains. Cannabinoid receptors are activated by three major groups of ligands: endocannabinoids; phytocannabinoids ; and synthetic cannabinoids. All endocannabinoids and phytocannabinoids are lipophilic.

<span class="mw-page-title-main">Peroxisome proliferator-activated receptor</span> Group of nuclear receptor proteins

In the field of molecular biology, the peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes. PPARs play essential roles in the regulation of cellular differentiation, development, and metabolism, and tumorigenesis of higher organisms.

<span class="mw-page-title-main">CYP2E1</span> Protein-coding gene in the species Homo sapiens

Cytochrome P450 2E1 is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. This class of enzymes is divided up into a number of subcategories, including CYP1, CYP2, and CYP3, which as a group are largely responsible for the breakdown of foreign compounds in mammals.

In chemistry, de novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation. For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as formate and aspartate. Methionine, on the other hand, is needed in the diet because while it can be degraded to and then regenerated from homocysteine, it cannot be synthesized de novo.

<span class="mw-page-title-main">Fatty-acid amide hydrolase 1</span>

Fatty-acid amide hydrolase 1 or FAAH-1(EC 3.5.1.99, oleamide hydrolase, anandamide amidohydrolase) is a member of the serine hydrolase family of enzymes. It was first shown to break down anandamide (AEA), an N-acylethanolamine (NAE) in 1993. In humans, it is encoded by the gene FAAH. FAAH also regulate the contents of NAE's in Dictyostelium discoideum, as they modulate their NAE levels in vivo through the use of a semispecific FAAH inhibitor.

<span class="mw-page-title-main">Apolipoprotein C-III</span> Protein-coding gene in the species Homo sapiens

Apolipoprotein C-III also known as apo-CIII, and apolipoprotein C3, is a protein that in humans is encoded by the APOC3 gene. Apo-CIII is secreted by the liver as well as the small intestine, and is found on triglyceride-rich lipoproteins such as chylomicrons, very low density lipoprotein (VLDL), and remnant cholesterol.

<span class="mw-page-title-main">Hepatic lipase</span> Mammalian protein found in Homo sapiens

Hepatic lipase (HL), also called hepatic triglyceride lipase (HTGL) or LIPC (for "lipase, hepatic"), is a form of lipase, catalyzing the hydrolysis of triacylglyceride. Hepatic lipase is coded by chromosome 15 and its gene is also often referred to as HTGL or LIPC. Hepatic lipase is expressed mainly in liver cells, known as hepatocytes, and endothelial cells of the liver. The hepatic lipase can either remain attached to the liver or can unbind from the liver endothelial cells and is free to enter the body's circulation system. When bound on the endothelial cells of the liver, it is often found bound to heparan sulfate proteoglycans (HSPG), keeping HL inactive and unable to bind to HDL (high-density lipoprotein) or IDL (intermediate-density lipoprotein). When it is free in the bloodstream, however, it is found associated with HDL to maintain it inactive. This is because the triacylglycerides in HDL serve as a substrate, but the lipoprotein contains proteins around the triacylglycerides that can prevent the triacylglycerides from being broken down by HL.

<span class="mw-page-title-main">Fatty acid-binding protein</span>

The fatty-acid-binding proteins (FABPs) are a family of transport proteins for fatty acids and other lipophilic substances such as eicosanoids and retinoids. These proteins are thought to facilitate the transfer of fatty acids between extra- and intracellular membranes. Some family members are also believed to transport lipophilic molecules from outer cell membrane to certain intracellular receptors such as PPAR. The FABPs are intracellular carriers that “solubilize” the endocannabinoid anandamide (AEA), transporting AEA to the breakdown by FAAH, and compounds that bind to FABPs block AEA breakdown, raising its level. The cannabinoids are also discovered to bind human FABPs that function as intracellular carriers, as THC and CBD inhibit the cellular uptake and catabolism of AEA by targeting FABPs. Competition for FABPs may in part or wholly explain the increased circulating levels of endocannabinoids reported after consumption of cannabinoids. Levels of fatty-acid-binding protein have been shown to decline with ageing in the mouse brain, possibly contributing to age-associated decline in synaptic activity.

<span class="mw-page-title-main">Peroxisome proliferator-activated receptor alpha</span> Nuclear receptor protein found in humans

Peroxisome proliferator-activated receptor alpha (PPAR-α), also known as NR1C1, is a nuclear receptor protein functioning as a transcription factor that in humans is encoded by the PPARA gene. Together with peroxisome proliferator-activated receptor delta and peroxisome proliferator-activated receptor gamma, PPAR-alpha is part of the subfamily of peroxisome proliferator-activated receptors. It was the first member of the PPAR family to be cloned in 1990 by Stephen Green and has been identified as the nuclear receptor for a diverse class of rodent hepatocarcinogens that causes proliferation of peroxisomes.

<span class="mw-page-title-main">Sterol regulatory element-binding protein 1</span> Protein-coding gene in the species Homo sapiens

Sterol regulatory element-binding transcription factor 1 (SREBF1) also known as sterol regulatory element-binding protein 1 (SREBP-1) is a protein that in humans is encoded by the SREBF1 gene.

<span class="mw-page-title-main">FABP2</span> Protein-coding gene in the species Homo sapiens

Fatty acid-binding protein 2 (FABP2), also known as Intestinal-type fatty acid-binding protein (I-FABP), is a protein that in humans is encoded by the FABP2 gene.

α-Parinaric acid Chemical compound

α-Parinaric acid is a conjugated polyunsaturated fatty acid. Discovered by Tsujimoto and Koyanagi in 1933, it contains 18 carbon atoms and 4 conjugated double bonds. The repeating single bond-double bond structure of α-parinaric acid distinguishes it structurally and chemically from the usual "methylene-interrupted" arrangement of polyunsaturated fatty acids that have double-bonds and single bonds separated by a methylene unit (−CH2−). Because of the fluorescent properties conferred by the alternating double bonds, α-parinaric acid is commonly used as a molecular probe in the study of biomembranes.

Sterol O-acyltransferase is an intracellular protein located in the endoplasmic reticulum that forms cholesteryl esters from cholesterol.

<span class="mw-page-title-main">FABP5</span> Protein-coding gene in the species Homo sapiens

Fatty acid-binding protein, epidermal is a protein that in humans is encoded by the FABP5 gene.

<span class="mw-page-title-main">FABP7</span> Protein-coding gene in the species Homo sapiens

Fatty acid binding protein 7, brain, is a human gene.

<span class="mw-page-title-main">FABP6</span> Mammalian protein found in Homo sapiens

Fatty acid binding protein 6, ileal (gastrotropin), also known as FABP6, is a protein which in humans is encoded by the FABP6 gene.

<span class="mw-page-title-main">Heart-type fatty acid binding protein</span> Protein-coding gene in the species Homo sapiens

Heart-type fatty acid binding protein (hFABP) also known as mammary-derived growth inhibitor is a protein that in humans is encoded by the FABP3 gene.

Endocannabinoid reuptake inhibitors (eCBRIs), also called cannabinoid reuptake inhibitors (CBRIs), are drugs which limit the reabsorption of endocannabinoid neurotransmitters by the releasing neuron.

The endocannabinoid transporters (eCBTs) are transport proteins for the endocannabinoids. Most neurotransmitters are water-soluble and require transmembrane proteins to transport them across the cell membrane. The endocannabinoids on the other hand, are non-charged lipids that readily cross lipid membranes. However, since the endocannabinoids are water immiscible, protein transporters have been described that act as carriers to solubilize and transport the endocannabinoids through the aqueous cytoplasm. These include the heat shock proteins (Hsp70s) and fatty acid-binding proteins for anandamide (FABPs). FABPs such as FABP1, FABP3, FABP5, and FABP7 have been shown to bind endocannabinoids. FABP inhibitors attenuate the breakdown of anandamide by the enzyme fatty acid amide hydrolase (FAAH) in cell culture. One of these inhibitors (SB-FI-26), isolated from a virtual library of a million compounds, belongs to a class of compounds that act as an anti-nociceptive agent with mild anti-inflammatory activity in mice. These truxillic acids and their derivatives have been known to have anti-inflammatory and anti-nociceptive effects in mice and are active components of a Chinese herbal medicine used to treat rheumatism and pain in human. The blockade of anandamide transport may, at least in part, be the mechanism through which these compounds exert their anti-nociceptive effects.

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Further reading