Homologous nuclear genes encode cytoplasmic and mitochondrial glutamine synthetase in Drosophila melanogaster

Caizzi, Ruggiero; Bozzetti, Maria Pia; Caggese, Corrado; Ritossa, Ferruccio

doi:10.1016/0022-2836(90)90301-2

Cited by 59 publications

(42 citation statements)

References 42 publications

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“…This is the case in Drosophila melanogaster, which contains two distinct GS genes (Caizzi et al, 1990): one encodes a GS isoform that contains a MTS and is targeted to the mitochondria, whereas the other encodes an isoform that lacks a MTS and is retained in the cytoplasm (Caizzi et al, 1990). Marine elasmobranchs and birds, which utilize the ureosmotic and uricotelic systems for ammonia detoxification, respectively, contain a single GS gene (Laud and Campbell, 1994;Patejunas and Young, 1987).…”

Section: Discussionmentioning

confidence: 99%

Weak mitochondrial targeting sequence determines tissue-specific subcellular localization of glutamine synthetase in liver and brain cells

Matthews

Gur

Koopman

et al. 2010

Journal of Cell Science

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SummaryEvolution of the uricotelic system for ammonia detoxification required a mechanism for tissue-specific subcellular localization of glutamine synthetase (GS). In uricotelic vertebrates, GS is mitochondrial in liver cells and cytoplasmic in brain. Because these species contain a single copy of the GS gene, it is not clear how tissue-specific subcellular localization is achieved. Here we show that in chicken, which utilizes the uricotelic system, the GS transcripts of liver and brain cells are identical and, consistently, there is no difference in the amino acid sequence of the protein. The N-terminus of GS, which constitutes a 'weak' mitochondrial targeting signal (MTS), is sufficient to direct a chimeric protein to the mitochondria in hepatocytes and to the cytoplasm in astrocytes. Considering that a weak MTS is dependent on a highly negative mitochondrial membrane potential () for import, we examined the magnitude of  in hepatocytes and astrocytes. Our results unexpectedly revealed that  in hepatocytes is considerably more negative than that of astrocytes and that converting the targeting signal into 'strong' MTS abolished the capability to confer tissue-specific subcellular localization. We suggest that evolutional selection of weak MTS provided a tool for differential targeting of an identical protein by taking advantage of tissue-specific differences in .

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Section: Discussionmentioning

confidence: 99%

Weak mitochondrial targeting sequence determines tissue-specific subcellular localization of glutamine synthetase in liver and brain cells

Matthews

Gur

Koopman

et al. 2010

Journal of Cell Science

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“…In Drosophila, there are two isoforms of GS, GS1 and GS2, which have 60% homology in their amino acid compositions. GS1 is localized in the mitochondria, whereas GS2 is localized in the cytosol (40). It has been reported that administering high levels of glutamine in cultured astrocytes induces mitochondrial permeability transition (41).…”

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confidence: 99%

Elevation of Glutamine Level by Selenophosphate Synthetase 1 Knockdown Induces Megamitochondrial Formation in Drosophila Cells

Shim

Kim

Jung

et al. 2009

Journal of Biological Chemistry

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Although selenophosphate synthetase 1 (SPS1/SelD) is an essential gene in Drosophila, its function has not been determined. To elucidate its intracellular role, we targeted the removal of SPS1/SelD mRNA in Drosophila SL2 cells using RNA interference technology that led to the formation of vacuole-like globular structures. Surprisingly, these structures were identified as megamitochondria, and only depolarized mitochondria developed into megamitochondria. The mRNA levels of l(2)01810 and glutamine synthetase 1 (GS1) were increased by SPS1/SelD knockdown. Blocking the expression of GS1 and l(2)01810 completely inhibited the formation of megamitochondria induced by loss of SPS1/SelD activity and decreased the intracellular levels of glutamine to those of control cells suggesting that the elevated level of glutamine is responsible for megamitochondrial formation. Overexpression of GS1 and l(2)01810 had a synergistic effect on the induction of megamitochondrial formation and on the synthesis of glutamine suggesting that l(2)01810 is involved in glutamine synthesis presumably by activating GS1. Our results indicate that, in Drosophila, SPS1/SelD regulates the intracellular glutamine by inhibiting GS1 and l(2)01810 expression and that elevated levels of glutamine lead to a nutritional stress that provides a signal for megamitochondrial formation.Selenium is an essential trace element in the diet of humans and many other life forms. It provides many health benefits such as roles in preventing cancer and heart disease, serving as an antiviral agent, stimulating the immune system, reactive oxygen species (ROS) 4 scavenging, and male reproduction (1-6). Many of the benefits of selenium are most likely due to the presence of this element in selenoproteins as the amino acid selenocysteine (Sec) (7-9). Sec is the 21st amino acid in the genetic code (10 -12) and is incorporated into selenoproteins in response to UGA Sec codons (13,14). The active donor of selenium in Sec biosynthesis is monoselenophosphate (15), which is synthesized from selenite and ATP by an enzyme designated as selenophosphate synthetase (SPS) (16). There are two isoforms of SPS in higher eukaryotes, SPS1/SelD and SPS2, whereas only one type of SPS (SelD) exists in lower eukaryotes and eubacteria (17). The sequences of SPS1/SelD and SPS2 are highly conserved. For example, the amino acid sequence homology between human SPS1/SelD and SPS2 is 72% and that between Drosophila SPS1/SelD and SPS2 is ϳ45%. One of the major differences between SPS1/SelD and SPS2 is that SPS1/ SelD has an arginine at the position corresponding to Sec in SPS2 (18,19).Initially, both SPS1/SelD and SPS2 were thought to be involved in selenophosphate synthesis. However, it was subsequently shown that only SPS2 catalyzes selenophosphate synthesis. In in vitro experiments, SPS2 synthesized selenophosphate from selenide and ATP, but SPS1/SelD did not have this activity (20). Knockdown of SPS2 in NIH3T3 cells led to the loss of selenoprotein biosynthesis, whereas the inhibition of SPS1/ SelD...

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“…Tg-GS has several ATTTA(G) motifs in a 3'-UTR, as do other species. The 3'-UTR length of 572 bp is longer than those in the Pacific oyster (280 bp) and sea anemone (Aiptasia pallida; 450 bp) (Smith et al, 2004) but shorter than those of other invertebrates such as D. melanogaster and A. aegypti (Caizzi et al, 1990;Smartt et al, 2001). Only one AATAAA was found in Tg-GS, suggesting that this transcript encodes only one protein.…”

Section: Discussionmentioning

confidence: 88%

“…Only one AATAAA was found in Tg-GS, suggesting that this transcript encodes only one protein. Mammals, fish, and birds also display only a single GS gene (Kuo and Darnell Jr., 1989;Wang et al, 1996), but some invertebrates, such as D. melanogaster, display two GS isozymes (Caizzi et al, 1990).…”

Section: Discussionmentioning

confidence: 99%

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Expression of glutamine synthetase in Tegillarca granosa (Bivalvia, Arcidae) hemocytes stimulated by Vibrio parahaemolyticus and lipopolysaccharides

Bao¹,

Li²,

Ye³

et al. 2013

Genet. Mol. Res.

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ABSTRACT. The blood cockle, Tegillarca granosa, is a widely consumed clam in the Indo-Pacific region. Glutamine synthetase (GS) is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. We identified the GS of T. granosa (Tg-GS) from hemocytes by 3'-and 5'-rapid amplification of cDNA ends (RACE)-PCR. The fulllength cDNA consisted of 1762 bp, with a 1104-bp open reading frame encoding 367 amino acids. Sequence comparison showed that Tg-GS has homology to GS of other organisms, with 79.78% identity with GS from the Pacific oyster Crassostrea gigas, 71.98% identity with GS from the zebrafish Danio rerio, and 68.96% identity with human Homo sapiens GS. A C-beta-Grasp domain and an N-catalytic domain were identified in Tg-GS, indicating that Tg-GS should be classified as a new member of the GS family. A quantitative RT-PCR assay was used to detect mRNA expression of Tg-GS in five different tissues. Higher levels of mRNA expression of GS were detected in the tissues of hemocytes and the mantle. Up-regulation of GS by challenge with the bacteria Vibrio parahaemolyticus and with bacterial wall lipopolysaccharides showed that GS plays a role in anti-bacterial immunity. We conclude that pathogen infection significantly induces expression level of Tg-GS, and that activation of GS influences the immune response of T. granosa by increasing glutamine concentration.

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Homologous nuclear genes encode cytoplasmic and mitochondrial glutamine synthetase in Drosophila melanogaster

Cited by 59 publications

References 42 publications

Weak mitochondrial targeting sequence determines tissue-specific subcellular localization of glutamine synthetase in liver and brain cells

Weak mitochondrial targeting sequence determines tissue-specific subcellular localization of glutamine synthetase in liver and brain cells

Elevation of Glutamine Level by Selenophosphate Synthetase 1 Knockdown Induces Megamitochondrial Formation in Drosophila Cells

Expression of glutamine synthetase in Tegillarca granosa (Bivalvia, Arcidae) hemocytes stimulated by Vibrio parahaemolyticus and lipopolysaccharides

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