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Structural and RNAi characterization of the German cockroach lipophorin receptor, and the evolutionary relationships of lipoprotein receptors.

ABSTRACT: BACKGROUND: Lipophorin receptors (LpRs) have been described in a number of insects, but functional studies have been reported only in locusts and mosquitoes. The aim of the present work was to characterize the LpR of the cockroach Blattella germanica, not only molecularly but also functionally using RNAi techniques, and to place LpRs in a phylogenetical context among lipoprotein receptors. RESULTS: We cloned a putative LpR from B. germanica (BgLpR) using RT-PCR methods. Two isoforms of BgLpR that differ from each other by an insertion/deletion of 24 amino acids were obtained from the fat body and the ovary. A phylogenetical analysis of lipoprotein receptors showed that BgLpR grouped with other sequences annotated as LpR in a cluster placed as a sister group of vertebrate low density lipoprotein receptors (LDLR) + lipoprotein receptor-related proteins 8 (LPR8) + vitellogenin receptors (VgR) + very low density lipoprotein receptors (VLDLR). The two BgLpR isoforms are expressed in different adult female tissues (fat body, ovary, brain, midgut, muscle) and in embryos. In ovaries and fat body, the two isoforms are similarly expressed during the first gonadotrophic cycle. mRNA levels in the fat body increase in parallel to vitellogenesis, whereas they decrease in the ovaries. BgLpR protein levels increase in parallel to vitellogenesis in both organs. Treatment with juvenile hormone increases BgLpR protein. RNAi experiments show that females with lower BgLpR expression have less lipophorin in the growing oocytes with respect to controls. CONCLUSION: The two isoforms of BgLpR are structurally similar to other LpRs. Phylogenetical analyses show that LpRs and the group formed by vertebrate LDLR + LPR8 + VgR + VLDLR, diverged from a common ancestor and diversified in parallel. The different expression patterns in the fat body and the ovary, comparing mRNA and protein, indicate that the corresponding mechanisms regulating BgLpR expression are different. Experiments with JH III suggest that such a hormone regulates the expression of BgLpR posttranscriptionally. RNAi experiments indicate that BgLpR is a functional lipophorin receptor.

SUBMITTER: Ciudad L

PROVIDER: S-EPMC1933434 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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Structural and RNAi characterization of the German cockroach lipophorin receptor, and the evolutionary relationships of lipoprotein receptors.

Ciudad Laura L Bellés Xavier X Piulachs Maria-Dolors MD

BMC molecular biology 20070622

<h4>Background</h4>Lipophorin receptors (LpRs) have been described in a number of insects, but functional studies have been reported only in locusts and mosquitoes. The aim of the present work was to characterize the LpR of the cockroach Blattella germanica, not only molecularly but also functionally using RNAi techniques, and to place LpRs in a phylogenetical context among lipoprotein receptors.<h4>Results</h4>We cloned a putative LpR from B. germanica (BgLpR) using RT-PCR methods. Two isoforms ...[more]

PMID: 17587448

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Project description:Extracellular solute-binding proteins of bacteria serve as chemoreceptors, recognition constituents of transport systems, and initiators of signal transduction pathways. Over 50 sequenced periplasmic solute-binding proteins of gram-negative bacteria and homologous extracytoplasmic lipoproteins of gram-positive bacteria have been analyzed for sequence similarities, and their degrees of relatedness have been determined. Some of these proteins are homologous to cytoplasmic transcriptional regulatory proteins of bacteria; however, with the sole exception of the vitamin B12-binding protein of Escherichia coli, which is homologous to human glutathione peroxidase, they are not demonstrably homologous to any of the several thousand sequenced eukaryotic proteins. Most of these proteins fall into eight distinct clusters as follows. Cluster 1 solute-binding proteins are specific for malto-oligosaccharides, multiple oligosaccharides, glycerol 3-phosphate, and iron. Cluster 2 proteins are specific for galactose, ribose, arabinose, and multiple monosaccharides, and they are homologous to a number of transcriptional regulatory proteins including the lactose, galactose, and fructose repressors of E. coli. Cluster 3 proteins are specific for histidine, lysine-arginine-ornithine, glutamine, octopine, nopaline, and basic amino acids. Cluster 4 proteins are specific for leucine and leucine-isoleucine-valine, and they are homologous to the aliphatic amidase transcriptional repressor, AmiC, of Pseudomonas aeruginosa. Cluster 5 proteins are specific for dipeptides and oligopeptides as well as nickel. Cluster 6 proteins are specific for sulfate, thiosulfate, and possibly phosphate. Cluster 7 proteins are specific for dicarboxylates and tricarboxylates, but these two proteins exhibit insufficient sequence similarity to establish homology. Finally, cluster 8 proteins are specific for iron complexes and possibly vitamin B12. Members of each cluster of binding proteins exhibit greater sequence conservation in their N-terminal domains than in their C-terminal domains. Signature sequences for these eight protein families are presented. The results reveal that binding proteins specific for the same solute from different bacteria are generally more closely related to each other than are binding proteins specific for different solutes from the same organism, although exceptions exist. They also suggest that a requirement for high-affinity solute binding imposes severe structural constraints on a protein. The occurrence of two distinct classes of bacterial cytoplasmic repressor proteins which are homologous to two different clusters of periplasmic binding proteins suggests that the gene-splicing events which allowed functional conversion of these proteins with retention of domain structure have occurred repeatedly during evolutionary history.(ABSTRACT TRUNCATED AT 400 WORDS)

Dataset Information

Structural and RNAi characterization of the German cockroach lipophorin receptor, and the evolutionary relationships of lipoprotein receptors.

Publications

Structural and RNAi characterization of the German cockroach lipophorin receptor, and the evolutionary relationships of lipoprotein receptors.

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