Cloning and characterization of the trout perforin

The pore-forming protein, perforin is one of the effectors of cell-mediated killing. A perforin cDNA clone was isolated from rainbow trout (Oncorhynchus mykiss) after screening of a spleen cDNA library. The full-length cDNA is 2070 bp in size, encoding for a polypeptide of 589 amino acids. The predicted amino acid sequence of the trout perforin is 64, 58 and 40% identical to those of Japanese flounder, zebrafish and human perforins, respectively. Although its membrane attack complex/perforin (MACPF) domain is conserved, trout perforin shows low homology to human and trout terminal complement components (C6, C7, C8 and C9), ranging from 19 to 26% identity. Expression analysis reveals that the trout perforin gene is expressed in the blood, brain, heart, kidney, intestine and spleen. Phylogenetic analysis of proteins which belong to the MACPF superfamily clusters the trout perforin in the same group with other known perforins.     

植物二酰甘油酰基转移酶基因(DGAT)研究进展

三酰甘油(TAG)是油料作物最主要的储藏脂类,二酰甘油酰基转移酶(DGAT,EC2.3.1.20)是TAG合成途径的限速酶,其主要作用是催化二酰甘油加上酰基脂肪酸形成三酰甘油.在植物中已发现了3种不同类型的DGAT基因,分别为DGAT1、DGAT2和DGAT3.该文对近年来国内外有关植物DGAT相关基因及其蛋白分类、定位、结构及其在脂肪酸合成、种子发育与萌发、幼苗发育、叶片新陈代谢等过程中的作用等研究进展进行综述.为提高油料作物种子油含量以及特定脂肪酸积累提供理论参考.     

Evolution of double MutT/Nudix domain-containing proteins: similar domain architectures from independent gene duplication-fusion events

The MutT/Nudix superfamily proteins repair DNA damage and play a role in human health and disease. In this study, we examined two different cases of double MutT/Nudix domain-containing proteins from eukaryotes and prokaryotes. Firstly, these double domain proteins were discovered in Drosophila, but only single Nudix domain proteins were found in other animals. The phylogenetic tree was constructed based on the protein sequence of Nudix_N and Nudix_C from Drosophila, and Nudix from other animals. The phylogenetic analysis suggested that the double Nudix domain proteins might have undergone a gene duplication-speciation-fusion process. Secondly, two genes of the MutT family, DR0004 and DR0329, were fused by two mutT gene segments and formed double MutT domain protein genes in Deinococcus radiodurans. The evolutionary tree of bacterial MutT proteins suggested that the double MutT domain proteins in D. radiodurans probably resulted from a gene duplication-fusion event after speciation. Gene duplication-fusion is a basic and important gene innovation mechanism for the evolution of double MutT/Nudix domain proteins. Independent gene duplication-fusion events resuited in similar domain architectures of different double MutT/Nudix domain proteins.     

Targeting tumors with LIGHT to generate metastasis-clearing immunity

Metastatic diseases cause the majority of morbidity and mortality of cancer patients. Established tumors form both physical and immunological barriers to limit immune detection and destruction. Current immunotherapy of vaccination and adoptive transfer shows limited effect at least in part due to the existing barriers in the tumors and depending on the knowledge of tumor antigens. Tumor necrosis factor (TNF) superfamily (TNFSF) member 14 (TNFSF14) LIGHT interacts with stromal cells, dendritic cells (DCs), NK cells, na?ve and activated T cells and tumor cells inside the tumor tissues via its two functional receptors, HVEM and lymphotoxin beta receptor (LTbetaR). Targeting tumor tissues with LIGHT leads to augmentation of priming, recruitment, and retention of effector cells at tumor sites, directly or indirectly, to induce strong anti-tumor immunity to inhibit the growth of primary tumors as well as eradicate metastases. Intratumor treatment would break tumor barriers and allow strong immunity against various tumors without defining tumor antigens. This review summarizes recent findings to support that LIGHT is a promising candidate for an effective cancer immunotherapy.     

Signaling through cholesterol esterification: a new pathway for the cholecystokinin 2 receptor involved in cell growth and invasion

Several studies indicate that cholesterol esterification is deregulated in cancers. The present study aimed to characterize the role of cholesterol esterification in proliferation and invasion of two tumor cells expressing an activated cholecystokinin 2 receptor (CCK2R). A significant increase in cholesterol esterification and activity of Acyl-CoA:cholesterol acyltransferase (ACAT) was measured in tumor cells expressing a constitutively activated oncogenic mutant of the CCK2R (CCK2R-E151A cells) compared with nontumor cells expressing the wild-type CCK2R (CCK2R-WT cells). Inhibition of cholesteryl ester formation and ACAT activity by Sah58-035, an inhibitor of ACAT, decreased by 34% and 73% CCK2R-E151A cell growth and invasion. Sustained activation of CCK2R-WT cells by gastrin increased cholesteryl ester production while addition of cholesteryl oleate to the culture medium of CCK2R-WT cells increased cell proliferation and invasion to a level close to that of CCK2R-E151A cells. In U87 glioma cells, a model of autocrine growth stimulation of the CCK2R, inhibition of cholesterol esterification and ACAT activity by Sah58-035 and two selective antagonists of the CCK2R significantly reduced cell proliferation and invasion. In both models, cholesteryl ester formation was found dependent on protein kinase zeta/ extracellular signal-related kinase 1/2 (PKCζ/ERK1/2) activation. These results show that signaling through ACAT/cholesterol esterification is a novel pathway for the CCK2R that contributes to tumor cell proliferation and invasion.     

Identification of two Drosophila TGF-β family members in the grasshopper Schistocerca americana

Intercellular signaling molecules of the transforming growth factor- (TGF-) superfamily are required for pattern formation in many multicellular organisms. The decapentaplegic (dpp) gene of Drosophila melanogaster has several developmental roles. To improve our understanding of the evolutionary diversification of this large family we identified dpp in the grasshopper Schistocerca americana. S. americana diverged from D. melanogaster approximately 350 million years ago, utilizes a distinct developmental program, and has a 60-fold-larger genome than D. melanogaster. Our analyses indicate a single dpp locus in D. melanogaster and S. americana, suggesting that dpp copy number does not correlate with increasing genome size. Another TGF- superfamily member, the D. melanogaster gene 60A, is also present in only one copy in each species. Comparison of homologous sequences from D. melanogaster, S. americana, and H. sapiens, representing roughly 900 million years of evolutionary distance, reveals significant constraint on sequence divergence for both dpp and 60A. In the signaling portion of the dpp protein, the amino acid identity between these species exceeds 74%. Our results for the TGF- superfamily are consistent with current hypotheses describing gene duplication and diversification as a frequent response to high levels of selective pressure on individual family members.     

A mutational analysis of active site residues in trans-3-chloroacrylic acid dehalogenase

trans-3-Chloroacrylic acid dehalogenase (CaaD) catalyzes the hydrolytic dehalogenation of trans-3-haloacrylates to yield malonate semialdehyde by a mechanism utilizing βPro-1, αArg-8, αArg-11, and αGlu-52. These residues are implicated in a promiscuous hydratase activity where 2-oxo-3-pentynoate is processed to acetopyruvate. The roles of three nearby residues (βAsn-39, αPhe-39, and αPhe-50) are unexplored. Mutants were constructed at these positions (βN39A, αF39A, αF39T, αF50A and αF50Y) and kinetic parameters determined along with those of the αR8K and αR11K mutants. Analysis indicates that αArg-8, αArg-11, and βAsn-39 are critical for dehalogenase activity whereas αArg-11 and αPhe-50 are critical for hydratase activity. Docking studies suggest structural bases for these observations.     

Deciphering structural aspects of reverse cholesterol transport: mapping the knowns and unknowns

Atherosclerosis is a major contributor to the onset and progression of cardiovascular disease (CVD). Cholesterol-loaded foam cells play a pivotal role in forming atherosclerotic plaques. Induction of cholesterol efflux from these cells may be a promising approach in treating CVD. The reverse cholesterol transport (RCT) pathway delivers cholesteryl ester (CE) packaged in high-density lipoproteins (HDL) from non-hepatic cells to the liver, thereby minimising cholesterol load of peripheral cells. RCT takes place via a well-organised interplay amongst apolipoprotein A1 (ApoA1), lecithin cholesterol acyltransferase (LCAT), ATP binding cassette transporter A1 (ABCA1), scavenger receptor-B1 (SR-B1), and the amount of free cholesterol. Unfortunately, modulation of RCT for treating atherosclerosis has failed in clinical trials owing to our lack of understanding of the relationship between HDL function and RCT. The fate of non-hepatic CEs in HDL is dependent on their access to proteins involved in remodelling and can be regulated at the structural level. An inadequate understanding of this inhibits the design of rational strategies for therapeutic interventions. Herein we extensively review the structure–function relationships that are essential for RCT. We also focus on genetic mutations that disturb the structural stability of proteins involved in RCT, rendering them partially or completely non-functional. Further studies are necessary for understanding the structural aspects of RCT pathway completely, and this review highlights alternative theories and unanswered questions.     

Plasma FA composition in familial LCAT deficiency indicates SOAT2-derived cholesteryl ester formation in humans

Mutations in the LCAT gene cause familial LCAT deficiency (Online Mendelian Inheritance in Man ID: #245900), a very rare metabolic disorder. LCAT is the only enzyme able to esterify cholesterol in plasma, whereas sterol O-acyltransferases 1 and 2 are the enzymes esterifying cellular cholesterol in cells. Despite the complete lack of LCAT activity, patients with familial LCAT deficiency exhibit circulating cholesteryl esters (CEs) in apoB-containing lipoproteins. To analyze the origin of these CEs, we investigated 24 carriers of LCAT deficiency in this observational study. We found that CE plasma levels were significantly reduced and highly variable among carriers of two mutant LCAT alleles (22.5 [4.0–37.8] mg/dl) and slightly reduced in heterozygotes (218 [153–234] mg/dl). FA distribution in CE (CEFA) was evaluated in whole plasma and VLDL in a subgroup of the enrolled subjects. We found enrichment of C16:0, C18:0, and C18:1 species and a depletion in C18:2 and C20:4 species in the plasma of carriers of two mutant LCAT alleles. No changes were observed in heterozygotes. Furthermore, plasma triglyceride-FA distribution was remarkably similar between carriers of LCAT deficiency and controls. CEFA distribution in VLDL essentially recapitulated that of plasma, being mainly enriched in C16:0 and C18:1, while depleted in C18:2 and C20:4. Finally, after fat loading, chylomicrons of carriers of two mutant LCAT alleles showed CEs containing mainly saturated FAs. This study of CEFA composition in a large cohort of carriers of LCAT deficiency shows that in the absence of LCAT-derived CEs, CEs present in apoB-containing lipoproteins are derived from hepatic and intestinal sterol O-acyltransferase 2.