scholarly journals Unconventional secretion of FABP4 by endosomes and secretory lysosomes

2017 ◽  
Vol 217 (2) ◽  
pp. 649-665 ◽  
Author(s):  
Julien Villeneuve ◽  
Laia Bassaganyas ◽  
Sebastien Lepreux ◽  
Marioara Chiritoiu ◽  
Pierre Costet ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Fatty Acid Binding Protein ◽  
Multivesicular Bodies ◽  
Fatty Acid Binding ◽  
Chloroquine Treatment ◽  
Wide Range ◽  
Unconventional Secretion ◽  
Extracellular Form ◽  
Secretory Lysosomes ◽  
Recent Demonstration

An appreciation of the functional properties of the cytoplasmic fatty acid binding protein 4 (FABP4) has advanced with the recent demonstration that an extracellular form secreted by adipocytes regulates a wide range of physiological functions. Little, however, is known about the mechanisms that mediate the unconventional secretion of FABP4. Here, we demonstrate that FABP4 secretion is mediated by a membrane-bounded compartment, independent of the conventional endoplasmic reticulum–Golgi secretory pathway. We show that FABP4 secretion is also independent of GRASP proteins, autophagy, and multivesicular bodies but involves enclosure within endosomes and secretory lysosomes. We highlight the physiological significance of this pathway with the demonstration that an increase in plasma levels of FABP4 is inhibited by chloroquine treatment of mice. These findings chart the pathway of FABP4 secretion and provide a potential therapeutic means to control metabolic disorders associated with its dysregulated secretion.

scholarly journals The binding of cholesterol and bile salts to recombinant rat liver fatty acid-binding protein

1996 ◽  
Vol 320 (3) ◽  
pp. 729-733 ◽  
Author(s):  
Alfred E. A. THUMSER ◽  
David C. WILTON
Keyword(s):  
Fatty Acid ◽  
Bile Salts ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Physiological Role ◽  
Lipid Binding ◽  
Liver Fatty Acid ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Wide Range

The physiological role of liver fatty acid-binding protein (L-FABP) has yet to be clarified. An important feature of this member of the family of intracellular lipid-binding proteins is the wide range of compounds that have been identified as potential physiological ligands. By using recombinant L-FABP, the binding of cholesterol, bile salts and their derivatives has been investigated under conditions that allow a direct comparison of the binding affinities of these ligands for fatty acids. The results demonstrate an inability of L-FABP to bind cholesterol, although the anionic derivative, cholesteryl sulphate, will bind under similar assay conditions. Of the bile salts examined, lithocholate and taurolithocholate sulphate showed the greatest binding to L-FABP. It is proposed that an important function of L-FABP is to bind certain physiological amphipathic anions, thus preventing the ‘free’ concentrations of these compounds from exceeding their critical micelle concentration, which could result in cell damage.

scholarly journals Effect on ligand binding of arginine mutations in recombinant rat liver fatty acid-binding protein

1994 ◽  
Vol 297 (1) ◽  
pp. 103-107 ◽  
Author(s):  
A E Thumser ◽  
C Evans ◽  
A F Worrall ◽  
D C Wilton
Keyword(s):  
Fatty Acid ◽  
Ligand Binding ◽  
Rat Liver ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Liver Fatty Acid ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Wide Range ◽  
Arginine Residues

Rat liver fatty acid-binding protein is able to accommodate a wide range of non-polar anions in addition to long-chain fatty acids. The two arginine residues of rat liver fatty acid-binding protein, Arg122 and Arg126, have been mutated and the effect of mutation on ligand binding investigated. No significant decrease in affinity for the fluorescent fatty acid analogue, 11-(5-dimethylaminonaphthalenesulphonyl amino)undecanoic acid, or oleate was observed. However, the apparent affinity for oleoyl-CoA was slightly increased with the mutations Ala122 and Gln122 such that oleoyl-CoA rather than oleate became the preferred ligand for these mutants. Small changes in protein stability were observed with the Arg122 mutations. The lack of notable ionic involvement of the conserved internal residue Arg122 in ligand binding is consistent with the hypothesis that the mode of ligand binding in liver fatty acid-binding protein is markedly different from that of other members of this lipid-binding protein family.

scholarly journals The binding of natural and fluorescent lysophospholipids to wild-type and mutant rat liver fatty acid-binding protein and albumin

1995 ◽  
Vol 307 (1) ◽  
pp. 305-311 ◽  
Author(s):  
A E A Thumser ◽  
D C Wilton
Keyword(s):  
Fatty Acid ◽  
Rat Liver ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Liver Fatty Acid ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Kd Values ◽  
Fluorescence Characteristics ◽  
Wide Range

Rat liver fatty acid-binding protein (FABP) is able to bind a wide range of non-polar anionic ligands, including lysophospholipids. In order to understand the nature of lysophospholipid interactions with liver FABP, the binding of natural lysophospholipids and two fluorescent analogues, N-(5-dimethylaminonaphthalenesulphonyl)-1-palmitoyl-sn-glycero-3- phosphoethanolamine (dansyl lysoPE) and 1-(O-[11-(5-dimethylaminonaphthalene-sulphonyl)amino]undecyl)-sn-glycero -3- phosphocholine (dansyl-C11-lysoPAF), has been investigated. The results confirmed the ability of liver FABP to bind lysophospholipids with KD values in the range of 1-2 microM, and a 1:1 binding stoichiometry was indicated. Binding of fluorescent lysophospholipids was enhanced with the FABP mutant, R122Q, possibly due to increased flexibility of the binding cavity as a result of reduced hydrogen-bonding constraints. The fluorescent lysophospholipids also bound to albumin, with KD values in the range 0.1-1.0 microM, and could be displaced by oleic acid. The fluorescence characteristics of the dansyl lysophospholipid analogue dansyl-C11-lyso-PAF suggested that this probe binds to the same site(s) on albumin as the fluorescent fatty acid probe 11-(5-dimethylaminonaphthalene-sulphonylamino)-undecanoic acid (DAUDA).

scholarly journals Unconventional Secretion of Adipocyte Fatty Acid Binding Protein 4 Is Mediated By Autophagic Proteins in a Sirtuin-1–Dependent Manner

Diabetes ◽  
2019 ◽  
Vol 68 (9) ◽  
pp. 1767-1777 ◽  
Author(s):  
Ajeetha Josephrajan ◽  
Ann V. Hertzel ◽  
Ellie K. Bohm ◽  
Michael W. McBurney ◽  
Shin-Ichiro Imai ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Sirtuin 1 ◽  
Dependent Manner ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Unconventional Secretion ◽  
Autophagic Proteins

scholarly journals Unconventional Secretion of Adipocyte Fatty Acid Binding Protein (FABP4) by Adipocytes

2018 ◽  
Vol 32 (S1) ◽  
Author(s):  
Ajeetha Josephrajan ◽  
Ann V. Hertzel ◽  
Douglas Mashek ◽  
Do‐Hyung Kim ◽  
Shin‐Ichiro Imai ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Unconventional Secretion

scholarly journals Studies on fatty acid-binding proteins. The binding properties of rat liver fatty acid-binding protein

1987 ◽  
Vol 247 (2) ◽  
pp. 485-488 ◽  
Author(s):  
T C Wilkinson ◽  
D C Wilton
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rat Liver ◽  
Fatty Acid Binding Protein ◽  
Unsaturated Fatty Acids ◽  
Binding Protein ◽  
Liver Fatty Acid ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Wide Range

1. The fluorescent fatty acid probe 11-(dansylamino)undecanoic acid binds to rat liver fatty acid-binding protein with a 1:1 stoichiometry. 2. The binding of the fluorescent probe is competitive with long-chain fatty acids. 3. Binding displacement studies were performed with a wide range of fatty acids and other ligands and identified C16 and C18 fatty acids as the preferred fatty acids for rat liver fatty acid-binding protein. No preference was observed for unsaturated fatty acids within this group. 4. Fatty acyl-CoA binds less well than the corresponding fatty acid.

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