Lipid-binding Protein Research Articles

Phosphorylation cycling of Annexin A2 Tyr23 is critical for calcium-regulated exocytosis in neuroendocrine cells

Annexin A2 (AnxA2) is a calcium and lipid binding protein involved in neuroendocrine secretion. We have previously demonstrated that AnxA2 participates in the formation and/or stabilization of lipid microdomains required for structural and spatial organization of the exocytotic machinery in chromaffin cells. However, the regulation of AnxA2 is not fully understood. Numerous phosphorylation sites have been identified in the amino-terminal domain of AnxA2. Phosphorylation of Ser25 and Tyr23 are well established and confirmed to be functionally significant. In particular, phosphorylation of Tyr23 by the tyrosine kinase pp60Src reduces the binding of AnxA2 to both actin filaments and the plasma membrane, two major actors of exocytosis, thus, we examined whether AnxA2 was phosphorylated on Tyr23 during exocytosis. Using immunolabelling and a biochemical approach, we found that nicotine stimulation triggered the phosphorylation of Anx A2 on Tyr23. The expression of two AnxA2 mutants carrying phosphorylation deficient (Y23A) or phosphomimetic (Y23E) mutations reduced the number exocytotic sites. Furthermore, expression of AnxA2-Y23A inhibited the formation of lipid microdomains, whereas the expression of AnxA2-Y23E altered actin filaments associated with docked granules. These results suggest that phosphorylation/dephosphorylation switch at Tyr23 in AnxA2 is critical for calcium-regulated exocytosis in neuroendocrine cells. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Determining the Lipid-Binding Specificity of SMP Domains: An ERMES Subunit as a Case Study.

Membrane contact sites between the endoplasmic reticulum (ER) and mitochondria function as a central hub for the exchange of phospholipids and calcium. The yeast Endoplasmic Reticulum-Mitochondrion Encounter Structure (ERMES) complex is composed of five subunits that tether the ER and mitochondria. Three ERMES subunits (i.e., Mdm12, Mmm1, and Mdm34) contain the synaptotagmin-like mitochondrial lipid-binding protein (SMP) domain. The SMP domain belongs to the tubular lipid-binding protein (TULIP) superfamily, which consists of ubiquitous lipid scavenging and transfer proteins. Herein, we describe the methods for expression and purification of recombinant Mdm12, a bona fide SMP-containing protein, together with the subsequent identification of its bound phospholipids by high-performance thin-layer chromatography (HPTLC) and the characterization of its lipid exchange and transfer functions using lipid displacement and liposome flotation in vitro assays with liposomes as model biological membranes. These methods can be applied to the study and characterization of novel lipid-binding and lipid-transfer proteins.

In Vitro Assays to Measure the Membrane Tethering and Lipid Transport Activities of the Extended Synaptotagmins.

The three extended synaptotagmins (E-Syts) are endoplasmic reticulum (ER)-localized membrane proteins that mediate tethering of the ER to the plasma membrane (PM) via C2 domain-dependent interactions regulated by Ca2+ and/or PI(4,5)P2. The E-Syts also contains a Synaptotagmin-like Mitochondrial lipid-binding Protein (SMP) domain, a lipid-harboring module through which they mediate lipid transport between the two adjacent membranes. Here, we describe in vitro liposome-based methods to study the membrane tethering and lipid transport functions of E-Syt1. Its membrane tethering activity is monitored through a turbidity-based assay, and its lipid transport property is analyzed via fluorescence resonance energy transfer (FRET)-based assay. These in vitro methods have enabled us to gain insight into the mechanism of action and regulation of E-Syt1, such as the role of Ca2+ in releasing E-Syt1 from an autoinhibitory conformation. The same methods could be adapted to the study of other lipid transport proteins that function at membrane contact sites.

Inhibiting Stearoyl-CoA Desaturase Ameliorates α-Synuclein Cytotoxicity

The lack of disease-modifying treatments for neurodegenerative disease stems in part from our rudimentary understanding of disease mechanisms and the paucity of targets for therapeutic intervention. Here we used an integrated discovery paradigm to identify a new therapeutic target for diseases caused by α-synuclein (α-syn), a small lipid-binding protein that misfolds and aggregates in Parkinson's disease and other disorders. Using unbiased phenotypic screening, we identified a series of compounds that were cytoprotective against α-syn-mediated toxicity by inhibiting the highly conserved enzyme stearoyl-CoA desaturase (SCD). Critically, reducing the levels of unsaturated membrane lipids by inhibiting SCD reduced α-syn toxicity in human induced pluripotent stem cell (iPSC) neuronal models. Taken together, these findings suggest that inhibition of fatty acid desaturation has potential as a therapeutic approach for the treatment of Parkinson's disease and other synucleinopathies.

SEC14L2, a lipid-binding protein, regulates HCV replication in culture with inter- and intra-genotype variations

The lipid-binding protein, SEC14L2, is crucial for the efficient viral replication of clinical hepatitis C virus (HCV) isolates in cell culture. Given the role of SEC14L2 in HCV replication, we aimed to study a large number of HCV positive sera carrying genotypes 1-4, to identify viral factors associated with efficient replication in culture. Additionally, we investigated whether 13 single nucleotide polymorphisms (SNPs) of SEC14L2 have an impact on RNA replication of naturally occurring HCV isolates. We generated Huh-7.5 cell lines overexpressing SEC14L2 or 13 coding SNPs and tested 73 different HCV positive sera for in vitro replication. Furthermore, we genotyped a cohort of 262 patients with chronic HCV for the common SNP (rs757660) and investigated its effect on the clinical phenotype. HCV isolates from genotype 1, 2, 3 and 4 replicate in Huh-7.5 cells overexpressing SEC14L2. Interestingly, only subgenomic replicons from genotypes 1 and 3 showed enhanced replication whereas genotypes 2 and 4 remained unaffected. Furthermore, replication was independent of viral load. Importantly, all tested SNPs supported HCV RNA replication in vitro, while 1 SNP was associated with decreased SEC1L2 expression and viral RNA. All SNPs exhibited comparable cellular cholesterol and vitamin E abundance in naïve Huh-7.5 cells. This large screen of natural HCV isolates of 4 genotypes underscores the relevance of SEC14L2 as an in vitro HCV host factor. Additionally, SEC14L2 variants appear to recapitulate the wild-type enhancement of HCV replication. Variant rs191341134 showed a decreased effect due to lowered stability, whereas variant rs757660, a high prevalence mutant, showed a similar phenotype to the wild-type. Until the year 2015, consistent replication of patient-derived isolates of hepatitis C virus (HCV) in an in vitro model remained a limitation in HCV research. In 2015 a group of authors identified a protein named SEC14L2 that enabled the replication of HCV isolates in cell culture. We performed a large screen encompassing 73 isolates of 4 different HCV genotypes. Additionally, we replaced the natural SEC14L2 with 13 different mutants to test if the protein variation significantly altered its HCV replication enhancing functions. We showed that different genotypes of HCV react differently to the presence of this protein and the variants of the protein mimic the behavior of the wild-type.

Identification and characterization of the promoter of a gene expressing mainly in the tapetum tissue of cotton (Gossypium hirsutum L.)

Anther and tapetum-specific genes are important for understanding male gametophyte development, as well as for their use in the development of barnase/barstar-gene based male sterility and restorer system for hybrid seed production. An essential component of the system is the availability of tapetum-specific promoters. In the present study, anther-specific genes were identified in cotton using microarray-based differential expression analysis, some of which show expression specific to the anthers at a stage where tapetum tissue was fully developed. Validation of the identified genes using RT-PCR and in situ hybridization identified one novel gene (AEG—Anther Expressing Gene) encoding a putative lipid binding protein as having a tapetum-specific expression. Further, three paralogs of the gene were identified in the cotton genome out of which the gene AEG1 (Anther Expressing Gene1) was found to express in the tapetum layer. Analysis of transgenic plants developed in cotton using 1.5 Kb promoter region of the of AEG1 gene fused upstream to the reporter gene β-glucuronidase revealed a broad window of expression of the AEG1 promoter in the tapetum tissue from the tetrad stage of anthers till the degeneration of the tapetum cells. Low levels of expression were also observed in the root tissues. Expression was not observed in the stem and leaves. The broad window of expression of AEG1 promoter in the tapetum tissue makes it a suitable candidate for the expression of the barstar gene for effective fertility restoration in the barnase/barstar system.

25-hydroxycholesterol down-regulates oxysterol binding protein like 2 (OSBPL2) via the p53/SREBF2/NFYA signaling pathway

Oxysterol Binding Protein Like 2 (OSBPL2) is a lipid-binding protein implicated in various cellular processes. Previous studies have shown that depression of OSBPL2 significantly increases the level of cellular 25-hydroxycholesterol (25-OHC) which regulates the expression of lipid-metabolism-related genes. However, whether 25-OHC can regulate the expression of OSBPL2 remains unanswered. This study aimed to explore the molecular mechanism of 25-OHC regulating the expression of OSBPL2. Using dual-luciferase reporter assay, we found a decrease of nuclear transcription factor Y subunit alpha (NFYA) bound with OSBPL2 promoter when HeLa cells were treated with 25-OHC. Furthermore, transcriptome sequencing and RNA interference results revealed that the p53/sterol regulatory element binding transcription factor 2 (SREBF2) signaling pathway was involved in the NFYA-dependent transcription of OSBPL2 induced by 25-OHC. Based on these results, we concluded that pleomorphic adenoma gene 1 (PLAG1) and NFYA participated in the basal transcription of OSBPL2 and that 25-OHC decreased the transcription of OSBPL2 via the p53/SREBF2/NFYA signaling pathway. 25-OHC will accumulate over time in OSBPL2 knockdown cells. These results may provide a new insight into the deafness caused by OSBPL2 mutation.

PHBV/PLA/Col-Based Nanofibrous Scaffolds Promote Recovery of Locomotor Function by Decreasing Reactive Astrogliosis in a Hemisection Spinal Cord Injury Rat Model.

Biomaterials are used to aid in the regeneration of damaged tissue and in promotion of axonal guidance following spinal cord injury (SCI). In the present study, electrospun composite poly(hydroxybutyrate-cohydroxyvalerate) (PHBV), poly(lactic acid) (PLA), and collagen (Col) nanofibrous scaffolds were applied to determine their roles in neural regeneration and recovery in a rat model of SCI. The morphological and chemical properties of the electrospun scaffolds were investigated. The growth and proliferation of astrocytes on the scaffolds were assessed by MTT assay. The differentiation and gene expression of astrocytes on the scaffolds were measured by immunofluorescence and quantitative real-time polymerase chain reaction (q-PCR) assays. In a rat spinal cord hemisection model with 3-mm defects, 80 Sprague-Dawley rats were randomly divided into five groups: Sham group, SCI group, SCI+PHBV/PLA group, SCI+PHBV/PLA/Col (70:30) group, and SCI+PHBV/PLA/Col (50:50) group. The Basso-Beattie-Bresnahan (BBB) scores were evaluated every week postsurgery, and (immuno) histological and protein analyses were performed on specimens at 8 weeks. PHBV/PLA/Col scaffolds strongly inhibited the activation of astrocytes without decreasing their proliferation. qPCR assays revealed significant increases in the expression of brain lipid-binding protein (BLBP), glutamate transporter 1 (GLT-1) and S100 calcium-binding protein B (S100-β), but decreases in the expression of glial fibrillary acidic protein (GFAP), chondroitin sulphate sulfate proteoglycan (CSPG), neurocan, and phosphacan in the PHBV/PLA/Col scaffold group. In a series of in vivo experiments, PHBV/PLA/Col scaffold-treated SCI groups showed significant reductions in the numbers of CD68- and GFAP-immunopositive astrocytes within the interface of the remodeled tissue layer, but increased expression of NF-200 in residual neurons with better locomotor functional recovery. However, there were no significant differences between the PHBV/PLA/Col (70:30) and PHBV/PLA/Col (50:50) groups, except in BBB scores. PHBV/PLA/Col nanofibrous scaffolds were biocompatible and significantly promoted astrocyte differentiation but decreased astrocyte activation. The topographic structures of the PHBV/PLA/Col (70:30 and 50:50) nanofibers were favorable for neural regeneration due to a decrease in astrogliosis in SCI rats.

Photoactivatable Myristic Acid Probes for UNC119-Cargo Interactions.

Protein myristoylation plays key roles in biological processes, for instance, in membrane attachment and activation of proteins and in mediating protein-protein and protein-lipid interactions. Furthermore, myristoylated proteins are involved in disorders, including cancer and viral infections. Therefore, new tools to study protein myristoylation are in high demand. Herein, we report the development of photoactivatable probes, based on a diazirine-substituted analogue of myristic acid. The probes bind to and, upon irradiation, covalently label the lipid-binding chaperone protein uncoordinated 119 (UNC119). UNC119 increases overall solubility and regulates specifically the transport of myristoylated proteins between intercellular membranes. The binding mode of the probes is similar to that of the myristate moiety, and the residues inside the hydrophobic pocket of UNC119 proteins that are critical for covalent binding have been identified. The interaction with UNC119 was also demonstrated in cell lysate by means of affinity enrichment. Moreover, it is shown that the myristate analogue can be incorporated into peptide substrates by N-myristoyl transferases of Leishmania and Trypanosoma protozoan parasites.

Cryo-electron microscopy structure of the lipid droplet-formation protein seipin.

Metabolic energy is stored in cells primarily as triacylglycerols in lipid droplets (LDs), and LD dysregulation leads to metabolic diseases. The formation of monolayer-bound LDs from the endoplasmic reticulum (ER) bilayer is poorly understood, but the ER protein seipin is essential to this process. In this study, we report a cryo-electron microscopy structure and functional characterization of Drosophila melanogaster seipin. The structure reveals a ring-shaped dodecamer with the luminal domain of each monomer resolved at ∼4.0 Å. Each luminal domain monomer exhibits two distinctive features: a hydrophobic helix (HH) positioned toward the ER bilayer and a β-sandwich domain with structural similarity to lipid-binding proteins. This structure and our functional testing in cells suggest a model in which seipin oligomers initially detect forming LDs in the ER via HHs and subsequently act as membrane anchors to enable lipid transfer and LD growth.

Hexosamine pathway regulates StarD7 expression in JEG-3 cells.

StarD7 is a lipid binding protein involved in the delivery of phosphatidylcholine to the mitochondria whose promoter is activated by Wnt/β-catenin signaling. Although the majority of glucose enters glycolysis, ~ 2-5% of it can be metabolized via the hexosamine biosynthetic pathway (HBP). Considering that HBP has been implicated in the regulation of β-catenin we explored if changes in glucose levels modulate StarD7 expression by the HBP in trophoblast cells. We found an increase in StarD7 as well as in β-catenin expression following high-glucose (25mM) treatment in JEG-3 cells; these effects were abolished in the presence of HBP inhibitors. Moreover, since HBP is able to promote unfolded protein response (UPR) the protein levels of GRP78, Ire1α, calnexin, p-eIF2α and total eIF2α as well as XBP1 mRNA was measured. Our results indicate that a diminution in glucose concentration leads to a decrease in StarD7 expression and an increase in the UPR markers: GRP78 and Ire1α. Conversely, an increase in glucose is associated to high StarD7 levels and low GRP78 expression, phospho-eIF2α and XBP1 splicing, although Ire1α remains high when cells are restored to high glucose. Taken together these findings indicate that glucose modulates StarD7 and β-catenin expression through the HBP associated to UPR, suggesting the existence of a link between UPR and HBP in trophoblast cells. This is the first study reporting the effects of glucose on StarD7 in trophoblast cells. These data highlight the importance to explore the role of StarD7 in placenta disorders related to nutrient availability.

HMGB1: LPS Delivery Vehicle for Caspase-11-Mediated Pyroptosis

Recognition of cytoplasmic lipopolysaccharide (LPS) by caspase-11 leads to pyroptosis and secretion of inflammatory mediators. In this issue of Immunity, Deng etal. (2018) report that high-mobility group box 1 (HMGB1) secreted by hepatocytes delivers extracellular LPS into the cytoplasm and mediates pyroptosis.

Molecular mechanisms of long-chain fatty acids absorption

The article presents about the role of several lipid-binding proteins expressed by the small intestine brush border membrane in the main steps of intestinal absorption of long-chain fatty acids and about changes in lipid profile caused by failed absorbtion. The system literature search is performed on Scopus databases, Web of Science, MedLine.

Expression of radial glial markers (GFAP, BLBP and GS) during telencephalic development in the catshark (Scyliorhinus canicula)

Radial glial cells (RGCs) are the first cell populations of glial nature to appear during brain ontogeny. They act as primary progenitor (stem) cells as well as a scaffold for neuronal migration. The proliferative capacity of these cells, both in development and in adulthood, has been subject of interest during past decades. In contrast with mammals where RGCs are restricted to specific ventricular areas in the adult brain, RGCs are the predominant glial element in fishes. However, developmental studies on the RGCs of cartilaginous fishes are scant. We have studied the expression patterns of RGCs markers including glial fibrillary acidic protein (GFAP), brain lipid binding protein (BLBP), and glutamine synthase (GS) in the telencephalic hemispheres of catshark (Scyliorhinus canicula) from early embryos to post-hatch juveniles. GFAP, BLBP and GS are first detected, respectively, in early, intermediate and late embryos. Expression of these glial markers was observed in cells with radial glia morphology lining the telencephalic ventricles, as well as in their radial processes and endfeet at the pial surface and their expression continue in ependymal cells (or tanycytes) in early juveniles. In addition, BLBP- and GS-immunoreactive cells morphologically resembling oligodendrocytes were observed. In late embryos, most of the GFAP- and BLBP-positive RGCs also coexpress GS and show proliferative activity. Our results indicate the existence of different proliferating subpopulations of RGCs in the embryonic ventricular zone of catshark. Further investigations are needed to determine whether these proliferative RGCs could act as neurogenic and/or gliogenic precursors.

Nucleus- and plastid-targeted annexin 5 promotes reproductive development in Arabidopsis and is essential for pollen and embryo formation

BackgroundPollen development is a strictly controlled post-meiotic process during which microspores differentiate into microgametophytes and profound structural and functional changes occur in organelles. Annexin 5 is a calcium- and lipid-binding protein that is highly expressed in pollen grains and regulates pollen development and physiology. To gain further insights into the role of ANN5 in Arabidopsis development, we performed detailed phenotypic characterization of Arabidopsis plants with modified ANN5 levels. In addition, interaction partners and subcellular localization of ANN5 were analyzed to investigate potential functions of ANN5 at cellular level.ResultsHere, we report that RNAi-mediated suppression of ANN5 results in formation of smaller pollen grains, enhanced pollen lethality, and delayed pollen tube growth. ANN5 RNAi knockdown plants also displayed aberrant development during the transition from the vegetative to generative phase and during embryogenesis, reflected by delayed bolting time and reduced embryo size, respectively. At the subcellular level, ANN5 was delivered to the nucleus, nucleolus, and cytoplasm, and was frequently localized in plastid nucleoids, suggesting a likely role in interorganellar communication. Furthermore, ANN5-YFP co-immunoprecipitated with RABE1b, a putative GTPase, and interaction in planta was confirmed in plastidial nucleoids using FLIM-FRET analysis.ConclusionsOur findings let us to propose that ANN5 influences basal cell homeostasis via modulation of plastid activity during pollen maturation. We hypothesize that the role of ANN5 is to orchestrate the plastidial and nuclear genome activities via protein-protein interactions however not only in maturing pollen but also during the transition from the vegetative to the generative growth and seed development.

Confidence to go the way science takes you.

Anne Simonsen is a Professor at the Department of Molecular Medicine at the Institute of Basic Medical Sciences of the University of Oslo, Norway. Her work focuses on lipid-binding proteins in membrane trafficking and autophagy, and their links to disease.

Green coffee bean extract and 5-O-caffeoylquinic acid regulate fat metabolism in Caenorhabditis elegans

Green coffee bean extract (GCBE) and chlorogenic acids are known to be associated with weight loss. 5-O-caffeoylquinic acid (5-CQA) is the main form of chlorogenic acid in GCBE. This study investigated GCBE and 5-CQA’s molecular mechanisms on fat metabolism using Caenorhabditis elegans as a model system. Treatment of GCBE or 5-CQA reduced triglycerides level by 29% and 23%, respectively, compared to the control. GCBE and 5-CQA’s fat-lowering effects were dependent on sbp-1 (an ortholog of mammalian sterol-regulatory-element-binding protein) and daf-16 (an ortholog of mammalian Forkhead box O transcription factor). Additionally, the lipid-binding protein, FAR-6, was identified as a target for GCBE and 5-CQA, along with other proteins. Therefore, GCBE and 5-CQA’s fat-lowering effects are dependent on sbp-1, daf-16 and far-6 in C. elegans, which are involved in lipogenesis, energy homeostasis and lipid uptake, respectively. These results suggest that chlorogenic acids are most likely responsible for GCBE’s fat-lowering effects.

A novel fatty acid-binding protein 5-estrogen-related receptor α signaling pathway promotes cell growth and energy metabolism in prostate cancer cells.

Epidermal or cutaneous fatty acid-binding protein is an intracellular lipid-binding protein, also known as FABP5, and its expression level is closely related to cancer cell proliferation and metastatic activities in various types of carcinoma. However, the molecular mechanisms of FABP5 in cancer cell proliferation and its other functions have remained unclear. In the present study, we have clearly revealed that FABP5 activated expression of metabolic genes (ATP5B, LCHAD, ACO2, FH and MFN2) via a novel signaling pathway in an ERRα (estrogen-related receptor α)-dependent manner in prostate cancer cell lines. To clarify the novel function of FABP5, we examined the activation mechanisms of the ERRα target genes via FABP5. A direct protein-protein interaction between FABP5 and ERRα was demonstrated by immunoprecipitation and GST pull-down assays. We have clearly revealed that FABP5 interacted directly with transcriptional complex containing ERRα and its co-activator PGC-1β to increase expression of the ERRα target genes. In addition, we have shown that FABP5 knockdown induced high energy stress leading to induction of apoptosis and cell cycle arrest via AMPK-FOXO3A signaling pathway in prostate cancer cells, suggesting that FABP5 plays an important role in cellular energy status directing metabolic adaptation to support cellular proliferation and survival.

Oxysterol-binding protein-related protein (ORP) 6 localizes to the ER and ER-plasma membrane contact sites and is involved in the turnover of PI4P in cerebellar granule neurons

Oxysterol-binding protein (OSBP)-related proteins (ORPs) are conserved lipid binding proteins found in organisms ranging from yeast to mammals. Recent findings have indicated that these proteins mainly localize to contact sites of 2 different membranous organelles. ORP6, a member of the ORP subfamily III, is one of the least studied ORPs. Using approaches in molecular cell biology, we attempted to study the characteristics of ORP6 and found that ORP6 is abundantly expressed in mouse cultured neurons. Deconvolution microscopy of cultured cerebellar granular cells revealed that ORP6 is localized to the endoplasmic reticulum (ER) and ER–plasma membrane (PM) contact sites, where it co-localized with extended synaptotagmin2 (E-Syt2), a well-known ER–PM contact site marker. E-Syt2 also co-localized with ORP3, another subfamily III member, and ORP5, a subfamily IV member. However, ORP5 does not distribute to the same ER-PM contact sites as subfamily III members. Also, the co-expression of ORP3 but not ORP5 altered the distribution of ORP6 into the processes of cerebellar neurons. Immunoprecipitation demonstrated binding between the intermediate region of ORP6 and ORP3 or ORP6 itself. Additionally, the localization of ORP6 in the PM decreased when co-expressed with the intermediate region of ORP6, in which the pleckstrin homology (PH) domain and OSBP-related ligand binding domain (ORD) are deleted. Over-expression of this intermediate region shifted the location of a phophtidylinositol-4-phosphate (PI4P) marker from the Golgi to the PM. Knockdown of ORP6 resulted in the same shift of the PI4P marker. Collectively, our data suggests that the recruitment of ORP6 to ER–PM contact sites is involved in the turnover of PI4P in cerebellar granular neurons.

Molecular cloning and tissue distribution of fatty acid binding protein-3 in goldfish (Carassius auratus) and its mRNA expression in response to cadmium and PAMPs

Fatty acid binding proteins (FABPs) are members of the conserved, multigene family of intracellular lipid binding proteins. In this study, the full-length cDNA of goldfish (Carassius auratus) FABP-3 (gfFABP-3) was successfully cloned. gfFABP-3 had an open reading frame of 402 bp and encoded a 133 amino acid polypeptide. The predicted gfFABP-3 protein included a lipocalin domain and displayed typical conserved FABP tertiary structures. Reverse transcription-PCR (RT-PCR) revealed that the gfFABP-3 gene was expressed in all tested tissues, with higher levels of expression in the testis, liver, heart, fat and kidney. After 24 h of cadmium exposure, gfFABP-3 was significantly upregulated in the gill, liver and spleen, but downregulated in the intestine, as compared to unexposed controls. gfFABP-3 expression was significantly downregulated in the spleen in goldfish challenged with LPS and Poly I:C. Our study provides a molecular characterization of goldfish FABP-3 and indicated that gfFABP-3 was potentially associated with the toxic effects of cadmium on lipid metabolism, and with the immune response to pathogenic infection.