The patatin-like lipase family in Gallus gallus

Appropriate cold stimulation changes energy distribution to improve stress resistance in broilers

Appropriate cold stimulation can improve stress resistance in broilers and alleviate the adverse impacts of a cold environment. To investigate the effects of intermittent mild cold stimulation (IMCS) on energy distribution in the livers of broilers, 96 healthy 1-d-old Ross-308 male broilers were randomly divided into the control group (CC) and the cold stimulation group (H5). The CC group was raised at a normal thermal temperature, i.e., 35 °C until 3 d, after which the temperature was dropped gradually by 0.5 °C/d until 20 °C at 33 d. This temperature was maintained until 49 d. The H5 group was raised at the same temperature as the CC group until 14 d (35 to 29.5 °C) and at 3 °C below the temperature of the CC group starting at 0930 hours for 5 h every other day from 15 to 35 d (26 to 17°C). The temperature was returned to 20 °C at 36 d and maintained until 49 d. At 50 d, all broilers were subjected to acute cold stress (ACS) at 10 °C for 6 and 12 h. We found that IMCS had positive effects on production performance. Using transcriptome sequencing of the broiler livers, 327 differentially expressed genes (DEG) were identified, and highly enriched in fatty acid biosynthesis, fatty acid degradation, and the pyruvate metabolism pathway. When compared to the CC group, the mRNA levels of ACAA1, ACAT2, ACSL1, CPT1A, LDHB, and PCK1 in the H5 group were increased at 22 d (P < 0.05). The LDHB mRNA level was upregulated in the H5 group at 29 d compared to the CC group (P < 0.05). After 21 d of IMCS (at 36 d), the mRNA expression levels of ACAT2 and PCK1 were found to be significantly increased in the H5 group compared to the CC group (P < 0.05). Seven days after the IMCS had ended (at 43 d), the mRNA levels of ACAA1, ACAT2, and LDHB in the H5 group were higher than in the CC group (P < 0.05). The mRNA levels of heat shock protein (HSP) 70, HSP90, and HSP110 in the H5 group were higher than in the CC group after 6 h of ACS (P < 0.05). The protein levels of HSP70 and HSP90 in the H5 group were downregulated after 12 h of ACS, compared to the CC group (P < 0.05). These results indicated that IMCS at 3 °C lower than the normal temperature could improve energy metabolism and stress resistance in the livers of broilers, alleviate the damage of short-term ACS on broilers, help broilers adapt to the low temperature, and maintain stable of energy metabolism in the body.

Acute Simian Varicella Virus Infection Causes Robust and Sustained Changes in Gene Expression in the Sensory Ganglia

Primary infection with varicella-zoster virus (VZV), a neurotropic alphaherpesvirus, results in varicella. VZV establishes latency in the sensory ganglia and can reactivate later in life to cause herpes zoster. The relationship between VZV and its host during acute infection in the sensory ganglia is not well understood due to limited access to clinical specimens. Intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV) recapitulates the hallmarks of VZV infection in humans. We leveraged this animal model to characterize the host-pathogen interactions in the ganglia during both acute and latent infection by measuring both viral and host transcriptomes on days postinfection (dpi) 3, 7, 10, 14, and 100. SVV DNA and transcripts were detected in sensory ganglia 3 dpi, before the appearance of rash. CD4 and CD8 T cells were also detected in the sensory ganglia 3 dpi. Moreover, lung-resident T cells isolated from the same animals 3 dpi also harbored SVV DNA and transcripts, suggesting that T cells may be responsible for trafficking SVV to the ganglia. Transcriptome sequencing (RNA-Seq) analysis showed that cessation of viral transcription 7 dpi coincides with a robust antiviral innate immune response in the ganglia. Interestingly, a significant number of genes that play a critical role in nervous system development and function remained downregulated into latency. These studies provide novel insights into host-pathogen interactions in the sensory ganglia during acute varicella and demonstrate that SVV infection results in profound and sustained changes in neuronal gene expression.

IMPORTANCE

Many aspects of VZV infection of sensory ganglia remain poorly understood, due to limited access to human specimens and the fact that VZV is strictly a human virus. Infection of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, provides a robust model of the human disease. Using this model, we show that SVV reaches the ganglia early after infection, most likely by T cells, and that the induction of a robust innate immune response correlates with cessation of virus transcription. We also report significant changes in the expression of genes that play an important role in neuronal function. Importantly, these changes persist long after viral replication ceases. Given the homology between SVV and VZV, and the genetic and physiological similarities between rhesus macaques and humans, our results provide novel insight into the interactions between VZV and its human host and explain some of the neurological consequences of VZV infection.

Identification mouse patatin-like phospholipase domain containing protein 1 as a skin-specific and membrane-associated protein

Patatin-like phospholipase domain containing protein 1 (PNPLA1) mutations have been identified to be associated with autosomal recessive congenital ichthyosis (ARCI) in recent years. However, its molecular characters have not been achieved until now. In the current study, the full length coding cDNA sequence of mouse PNPLA1 (mPNPLA1) was identified firstly. There were several putative transmembrane domains (TMDs) in mPNPLA1 by bioinformation analysis. mPNPLA1 was further found to be expressed exclusively in the membrane fraction in mammalian cells. However, it did not colocalized with the endoplasmic reticulum (ER) or lipid droplets (LDs). Moreover, the mRNA levels of mPNPLA1 was detected to be highly expressed in the skin, while very weak or even less in other mouse tissues by quantitative PCR. In addition, based on experiments with inhibitors and inducer of protein degradation pathways, mPNPLA1 was demonstrated to be degraded by macroautophagy, but not by the proteasome. These results indicated PNPLA1 was a skin-specific and membrane-associated protein for the first time, suggesting that it may mainly play a role in the skin.

Identification of human patatin-like phospholipase domain-containing protein 1 and a mutant in human cervical cancer HeLa cells

Recently members of mammalian patatin-like phospholipase domain containing (PNPLA) protein family have attracted attention for their critical roles in diverse aspects of lipid metabolism and signal pathway. Until now little has been known about the characteristics of PNPLA1. Here, the full length coding cDNA sequence of human PNPLA1 (hPNPLA1) was cloned for the first time, which encoded a polypeptide with 532 amino acids containing the whole patatin domain. Tissue expression profiles analysis showed that low mRNA levels of hPNPLA1 existed in various tissues, except high expression in the digestive system, bone marrow and spleen. Subcellular distribution of hPNPLA1 tagged with green fluorescence protein mainly localized to lipid droplets. Furthermore, a nonsense mutation of PNPLA1 in human cervical cancer HeLa cells was identified. The hPNPLA1 mutant encoded a protein of 412 amino acids without the C-terminal domain and did not colocalize to lipid droplets, which suggested that the C-terminal region of hPNPLA1 affected lipid droplet binding. These results identified hPNPLA1 and a mutant in HeLa cells, and provided insights into the structure and function of PNPLA1.

Dynamics of PPARs, fatty acid metabolism genes and lipid classes in eggs and early larvae of a teleost

Dietary long chain polyunsaturated fatty acids (FA) have been recognized of crucial importance in early development of vertebrates, contributing to the impressive morphological and physiological changes both as building blocks and to energy production. The importance of lipids along development depends on ontogenetic, phylogenetic and environmental parameters. The expression patterns of FA metabolism genes have not been characterized in developing fish embryos nor compared to lipid class profiles. Full lipid metabolism only occurred after hatching, as revealed by alterations in lipid profiles and FA gene expression. Nonetheless, transcriptional changes of some FA genes were already present in embryos at notochord formation. Many genes displayed an expression profile opposed to the decrease of lipids along the development, while others responded solely to starvation. Transcription of most genes involved in FA metabolism had a strong correlation to PPARs' mRNA levels (α1, α2, β, γ). The comparison of mRNA expression of the genes with the lipid profiles produced new insights into the FA metabolism and regulation during the development of turbot larvae, providing the basis for future studies including comparative approaches with other vertebrate species.

Fluoroketone inhibition of Ca(2+)-independent phospholipase A2 through binding pocket association defined by hydrogen/deuterium exchange and molecular dynamics

The mechanism of inhibition of group VIA Ca²⁺-independent phospholipase A₂ (iPLA₂) by fluoroketone (FK) ligands is examined by a combination of deuterium exchange mass spectrometry (DXMS) and molecular dynamics (MD). Models for iPLA₂ were built by homology with the known structure of patatin and equilibrated by extensive MD simulations. Empty pockets were identified during the simulations and studied for their ability to accommodate FK inhibitors. Ligand docking techniques showed that the potent inhibitor 1,1,1,3-tetrafluoro-7-phenylheptan-2-one (PHFK) forms favorable interactions inside an active-site pocket, where it blocks the entrance of phospholipid substrates. The polar fluoroketone headgroup is stabilized by hydrogen bonds with residues Gly486, Gly487, and Ser519. The nonpolar aliphatic chain and aromatic group are stabilized by hydrophobic contacts with Met544, Val548, Phe549, Leu560, and Ala640. The binding mode is supported by DXMS experiments showing an important decrease of deuteration in the contact regions in the presence of the inhibitor. The discovery of the precise binding mode of FK ligands to the iPLA₂ should greatly improve our ability to design new inhibitors with higher potency and selectivity.

Polymorphisms of the PNPLA3 gene and their associations with chicken growth and carcass traits

1. An F(2) resource population of Gushi chickens crossed with Anka broilers was used to investigate the genetic effects of the chicken PNPLA3 gene on growth and adipose accumulation. 2. Associations between three SNPs (g.40006G > T, g.42344T > C and g.42404A > T) and broiler traits were determined using linkage disequilibrium, haplotype construction and association analysis. 3. The g.40006G > T mutation was associated with body weights at 4, 6, 8, 10 and 12 weeks of age, carcass weight, evisceration weight and semi-evisceration weight (P < 0.05). 4. Haplotypes of the g.42344T > C and g.42404A > T mutations were associated with body weight at 12 weeks, carcass weight, evisceration weight, and semi-evisceration weight (P < 0·05) and were associated with significant dominance effects. 5. The results suggest that the PNPLA3 gene may be in linkage with the causative mutation or a QTL controlling growth traits in chickens. In contrast to human studies, the polymorphisms were not associated with fat related traits.

Vertebrate patatin-like phospholipase domain-containing protein 4 (PNPLA4) genes and proteins: a gene with a role in retinol metabolism

At least eight families of mammalian patatin-like phospholipase domain-containing proteins (PNPLA) (E.C. 3.1.1.3) catalyse the hydrolysis of triglycerides, including PNPLA4 (alternatively PLPL4 or GS2), which also acts as a retinol transacylase and participates in retinol-ester metabolism in the body. Bioinformatic methods were used to predict the amino acid sequences, secondary and tertiary structures and gene locations for PNPLA4 genes and encoded proteins using data from several vertebrate genome projects. PNPLA4 genes were located on the X-chromosome for the eutherian mammalian genomes examined. Opossum (marsupial), chicken, anole lizard, clawed toad, zebrafish and lancelet PNPLA4 genes were also identified. Most vertebrate PNPLA4 genes typically contained six coding exons whereas the lancelet PNPLA4 gene contained five coding exons. PNPLA4 subunits were the smallest among the PNPLA-like proteins examined containing 252–255 residues, shared >64 % sequence identities and key amino acid residues and predicted motifs, including ‘patatin’ (residues 6–176); putative catalytic dyad active site residues, Ser43 and Asp163; oxy-anion ‘hole’ residues (10–15); and conserved serine residues, which may perform structural roles for this enzyme. Predicted tertiary structures for PNPLA4 ‘patatin’ were similar to those reported for potato ‘patatin’, suggesting that it is strongly conserved during evolution. Human PNPLA4 contained a CpG49 island within the gene promoter, a miRNA-186 binding site within the mRNA 3′-noncoding region for the PNPLA4b isoform and exhibited wide tissue expression at a higher than average level. These and previous studies of vertebrate PNPLA-like gene families have suggested that PNPLA4 is an ancient gene in evolution which has resulted from a duplication of an ancestral invertebrate ATGL-like gene (encoding adipose triglyceride lipase).

Degradation of mouse NTE-related esterase by macroautophagy and the proteasome

NTE-related esterase (NRE) is a novel endoplasmic reticulum-anchored lysophospholipase with high homology to neuropathy target esterase (NTE). However, little is known about the regulation of NRE protein. In the current study, we investigated the degradation pathways of mouse NRE (mNRE) in mammalian cells. Based on experiments with inhibitors and inducer of protein degradation pathways, we provide here the first evidence that mNRE is degraded by macroautophagy as well as by the proteasome. Moreover, the contribution of protein domains to the degradation of mNRE was investigated, which showed that the transmembrane and regulatory domain played a role in the degradation of mNRE by macroautophagy and the proteasome respectively. In contrast the C-terminal catalytic domain was not involved in both degradation pathways of mNRE. These findings showed for the first time that the degradation pathways in controlling mNRE quantity and may provide further insight into structure and regulation of mNRE.

Recent insights into the structure and function of comparative gene identification-58

PURPOSE OF REVIEW

Comparative gene identification-58 (CGI-58) is an important player in lipid metabolism. It acts as activator of triglyceride hydrolases and as acyl-CoA-dependent lysophosphatidic acid acyltransferase. This review aims at establishing a structure-function relationship of this still rather enigmatic protein based on recent studies characterizing different functions of CGI-58.

RECENT FINDINGS

Novel studies confirm the important regulatory role of CGI-58 as activator of the triglyceride hydrolase adipose triglyceride lipase. New evidence, corroborated by the characterization of a CGI-58 knockout mouse model, also suggests the existence of yet unknown lipases that are activated by CGI-58. Additionally, CGI-58 was identified to exert acyl-CoA-dependent lysophosphatidic acid acyltransferase activity, which implies possible roles in triglyceride or phospholipid synthesis or signaling processes. Unlike mammalian CGI-58 proteins, orthologs from plants and yeast additionally act as weak triglyceride and phospholipid hydrolases. A first three-dimensional model was calculated and allows preliminary structural considerations for the functions of CGI-58.

SUMMARY

Despite important progress concerning the different biochemical functions of CGI-58, the physiological importance of these activities requires better characterization. Furthermore, three-dimensional structural data for CGI-58 are required to unveil the molecular mechanism of how CGI-58 acts as activator of lipases and exerts its enzymatic functions.

Enzymes involved in hepatic acylglycerol metabolism in the chicken

In laying hens, massive hepatic mobilization of fatty acids is required for the synthesis of oocyte-targeted very-low density lipoproteins (VLDL). The current study aims at identification of enzymes that hydrolyze hepatic acylglycerol stores regulated in a fashion compatible with supporting enhanced VLDL synthesis. We show that unlike mammals, chickens express adipose triglyceride lipase (ATGL) also in liver, where it is upregulated by fasting, while the enzyme patatin-like phospholipase domain-containing lipase 3 (PNPLA3) is suppressed. For the first time in any system, we show that hepatic arylacetamide deacetylase (AADA) is upregulated by fasting, and that its affinity for an insoluble carboxylester substrate is compatible with an in-vivo function similar to that of ATGL. Unknown heretofore, hepatic expression of chicken AADA is estrogen-responsive, and is induced to the same degree as the stimulation of VLDL-production by estrogen. These observations support roles of chicken ATGL, PNPLA3, and AADA in acylglycerol metabolism related to the high rates of VLDL synthesis that are essential for reproduction.

Lipolysis - a highly regulated multi-enzyme complex mediates the catabolism of cellular fat stores

Lipolysis is the biochemical pathway responsible for the catabolism of triacylglycerol (TAG) stored in cellular lipid droplets. The hydrolytic cleavage of TAG generates non-esterified fatty acids, which are subsequently used as energy substrates, essential precursors for lipid and membrane synthesis, or mediators in cell signaling processes. Consistent with its central importance in lipid and energy homeostasis, lipolysis occurs in essentially all tissues and cell types, it is most abundant, however, in white and brown adipose tissue. Over the last 5years, important enzymes and regulatory protein factors involved in lipolysis have been identified. These include an essential TAG hydrolase named adipose triglyceride lipase (ATGL) [annotated as patatin-like phospholipase domain-containing protein A2], the ATGL activator comparative gene identification-58 [annotated as α/β hydrolase containing protein 5], and the ATGL inhibitor G0/G1 switch gene 2. Together with the established hormone-sensitive lipase [annotated as lipase E] and monoglyceride lipase, these proteins constitute the basic "lipolytic machinery". Additionally, a large number of hormonal signaling pathways and lipid droplet-associated protein factors regulate substrate access and the activity of the "lipolysome". This review summarizes the current knowledge concerning the enzymes and regulatory processes governing lipolysis of fat stores in adipose and non-adipose tissues. Special emphasis will be given to ATGL, its regulation, and physiological function.

Associations of ATGL gene polymorphisms with chicken growth and fat traits

Adipose triglyceride lipase (ATGL) catalyses the initial step in triglyceride hydrolysis, so the ATGL gene is a candidate for growth and fat traits in chickens. Nine reported single-nucleotide polymorphisms (SNPs) located in 3 exons of the chicken ATGL gene were chosen for genotyping an F2 population. Only 5 SNPs were confirmed for polymorphisms and used for association analyses. The results show that c.531G>A (p.E177Syn) was not associated with any growth and fat traits (P > 0.05), but c.782G>A (p.S261N) was associated with body weight (BW) on days 14, 21, 35, 63, 70, 77, cingulated fat width and abdominal fat pad weight (P < 0.05), and significantly associated with BW on days 42, 49, and 56 (P < 0.01). Significant associations of c.903C>T (p.F301Syn) with BW on days 49 and 77 days and crude protein content of breast muscle (P < 0.05), and c.1164G>A (p.K388Syn) with BW on day 7 (P < 0.05) were also detected. Additionally, c.1069T>C (p.L357Syn) was associated with breast muscle colour (P < 0.05), and significantly associated with crude fat (ether extract) content of breast muscle (P < 0.01). Thus the missense SNP of c.782G>A (p.S261N) was significantly associated with the largest number of chicken growth and fat traits in this study.

Multiple functions as lipase, steryl ester hydrolase, phospholipase, and acyltransferase of Tgl4p from the yeast Saccharomyces cerevisiae

Triacylglycerol (TAG) hydrolysis, membrane lipid biosynthesis, and lipid turnover are largely interlinked processes. In yeast, TAG is mobilized by three TAG lipases named Tgl3p, Tgl4p, and Tgl5p, which are localized to lipid particles/droplets. These TAG lipases posses a conserved GXSXG motif that is characteristic of hydrolytic enzymes. Here, we demonstrated that the yeast TAG lipase Tgl4p, the functional ortholog of the adipose TAG lipase, ATGL, catalyzes multiple functions in lipid metabolism. An extended domain and motif search analysis revealed that Tgl4p bears not only a lipase consensus domain but also a conserved motif for calcium-independent phospholipase A(2). We show that Tgl4p exhibits TAG lipase, steryl ester hydrolase, and phospholipase A(2) activities, but surprisingly it also catalyzed the acyl-CoA-dependent acylation of lysophosphatidic acid to phosphatidic acid (PA). Heterologous overexpression of Tgl4p in Pichia pastoris increased total phospholipid and specifically PA synthesis. Moreover, deletion of TGL4 in Saccharomyces cerevisiae showed an altered pattern of phosphatidylcholine and PA molecular species. Altogether, our data suggest that yeast Tgl4p functions as a hydrolytic enzyme in lipid degradation but also contributes to fatty acid channeling and phospholipid remodeling.

Avian phospholipid transfer protein causes HDL conversion without affecting cholesterol efflux from macrophages

Circulatory phospholipid transfer protein (PLTP) has two major functions: 1) transfer of phospholipids towards HDL particles; and 2) modulation of HDL size and composition via the HDL conversion process. In the laying hen (Gallus gallus), the massive oocyte-targeted lipid flow is achieved through the concerted actions of lipases, lipid transfer proteins, and relatives of the LDL receptor family. The aim of the study was to gain insights into the structure and functions of chicken PLTP. The results demonstrate that PLTP is highly conserved from chicken to mammals, as (i) chicken PLTP is associated with plasma HDL; (ii) it clearly possesses phospholipid transfer activity; (iii) it is inactivated at +58 degrees C; and (iv) it mediates conversion of avian and human HDL into small prebeta-mobile HDL and large fused alpha-mobile HDL particles. Our data show that HDL from different chicken models is similar in chemical and physical properties to that of man based on PLTP activity, cholesterol efflux, and HDL conversion assays. In contrast to mammals, PLTP-facilitated HDL remodeling did not enhance cholesterol efflux efficiency of chicken HDL particles.

Identification and characterization of chicken neuropathy target esterase

Neuropathy target esterase (NTE) was proposed as the initial target during the process of organophosphate-induced delayed neuropathy (OPIDN) and adult hens are the animal model of OPIDN. However, little has been known about the sequence and characteristics of chicken NTE. Here, we firstly identified the full length cDNA of chicken NTE (cNTE), which contained an open reading frame of 3966 nucleotides encoding 1321 amino acids. Chicken NTE had two distinct regions, one was the regulatory domain (cNTER) and the other was the catalytic domain (cNEST). Over-expression of cNTER in mammalian cells did not show any NTE activity, whereas cNEST had NTE activity. Cells expressing cNTER tagged with green fluorescent protein (GFP) showed accumulation of cNTER-GFP in an endoplasmic reticulum-like localization pattern. In addition, macroautophagy and the proteasome pathways were found to be involved in the degradation of cNTER, but not cNEST. These results first showed that cNTE was an ER-anchored protein and degraded by macroautophagy as well as the proteasome.

Adipose triglyceride lipase and the lipolytic catabolism of cellular fat stores

Fatty acids (FAs) are essential components of all lipid classes and pivotal substrates for energy production in all vertebrates. Additionally, they act directly or indirectly as signaling molecules and, when bonded to amino acid side chains of peptides, anchor proteins in biological membranes. In vertebrates, FAs are predominantly stored in the form of triacylglycerol (TG) within lipid droplets of white adipose tissue. Lipid droplet-associated TGs are also found in most nonadipose tissues, including liver, cardiac muscle, and skeletal muscle. The mobilization of FAs from all fat depots depends on the activity of TG hydrolases. Currently, three enzymes are known to hydrolyze TG, the well-studied hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL), discovered more than 40 years ago, as well as the relatively recently identified adipose triglyceride lipase (ATGL). The phenotype of HSL- and ATGL-deficient mice, as well as the disease pattern of patients with defective ATGL activity (due to mutation in ATGL or in the enzyme's activator, CGI-58), suggest that the consecutive action of ATGL, HSL, and MGL is responsible for the complete hydrolysis of a TG molecule. The complex regulation of these enzymes by numerous, partially uncharacterized effectors creates the "lipolysome," a complex metabolic network that contributes to the control of lipid and energy homeostasis. This review focuses on the structure, function, and regulation of lipolytic enzymes with a special emphasis on ATGL.