Adipokinetic hormone controls lipid metabolism in adults and carbohydrate metabolism in larvae of Manduca sexta

Ziegler, Rolf; Eckart, Klaus; Law, John H.

doi:10.1016/0196-9781(90)90030-9

Cited by 64 publications

(36 citation statements)

References 17 publications

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“…In M. sexta, the effect of AKH on the mobilization of energy reserves is dependent on the developmental stage. During the larval stage, AKH mobilizes glycogen through the activation of glycogen-phosphorylase, whereas it promotes a massive lipolytic response in the adult stage (12). The lipolytic response induced by AKH is associated with a rapid activation of fat body cAMPdependent protein kinase A (PKA) and a sustained increase in calcium influx (13).…”

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confidence: 99%

The main triglyceride-lipase from the insect fat body is an active phospholipase A1: identification and characterization

Arrese

Patel

Soulages

2006

Journal of Lipid Research

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The main triglyceride-lipase (TG-lipase) from the fat body of Manduca sexta has been identified as the homolog of Drosophila melanogaster CG8552. This protein is conserved among insects and also shares significant sequence similarity with vertebrate phospholipases (PLs) from the phosphatidic acid preferring-phospholipase A1 (PA-PLA 1 ) family. It is shown here that the TG-lipase is also a PL. TGlipase and PL activities copurify and are inhibited by, or resistant to, the same lipase inhibitors, indicating that both activities are catalyzed by the same enzyme and active site. The PL activity of TG-lipase corresponded to PL type A 1 . The concentration dependence of lipase activity with TG and PL micellar substrates showed saturation kinetics, with apparent K m values of 152 6 11 and 7.8 6 1.1 mM, respectively. TG-lipase was able to hydrolyze the major phospholipid components of the lipid droplets, phosphatidylcholine and phosphatidylethanolamine. The enzyme hydrolyzes 77 molecules of TG for every molecule of PL contained in the lipid droplets. It was observed that the activation of lipolysis in vivo is accompanied by activation of the hydrolysis of phospholipids of the lipid droplets. These results suggest that the PL activity of the insect TG-lipase could be required to allow access of the lipase to TG molecules contained in the core of the lipid droplets.-Arrese, E. L., R. T. Patel, and J. L. Soulages. The main triglyceride-lipase from the insect fat body is an active phospholipase A 1 : identification and characterization.

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confidence: 99%

The main triglyceride-lipase from the insect fat body is an active phospholipase A1: identification and characterization

Arrese

Patel

Soulages

2006

Journal of Lipid Research

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“…These receptors are related to the mammalian gonadotropin-releasing hormone receptor, which is a G protein-coupled receptor that activates both inositol phosphate and cAMP signaling responses. In M. sexta, AKH mobilizes glycogen during the larval stages and promotes a massive lipolytic response in the adult stage (19). AKH promotes a rapid activation of fat body cAMP-dependent protein kinase A (PKA).…”

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confidence: 99%

Activation of the Lipid Droplet Controls the Rate of Lipolysis of Triglycerides in the Insect Fat Body

Patel

Soulages

Hariharasundaram

et al. 2005

Journal of Biological Chemistry

102

127

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The hydrolysis of triglyceride (TG) stored in the lipid droplets of the insect fat body is under hormonal regulation by the adipokinetic hormone (AKH), which triggers a rapid activation cAMP-dependent kinase cascade (protein kinase A (PKA)). The role of phosphorylation on two components of the lipolytic process, the TG-lipase and the lipid droplet, was investigated in fat body adipocytes. The activity of purified TG-lipase determined using in vivo TG-radiolabeled lipid droplets was unaffected by the phosphorylation of the lipase. However, the activity of purified lipase was 2.4-fold higher against lipid droplets isolated from hormone-stimulated fat bodies than against lipid droplets isolated from unstimulated tissue. In vivo stimulation of lipolysis promotes a rapid phosphorylation of a lipid droplet protein with an apparent mass of 42-44 kDa. This protein was identified as "Lipid Storage Droplet Protein 1" (Lsdp1). In vivo phosphorylation of this protein reached a peak ϳ10 min after the injection of AKH. Supporting a role of Lsdp1 in lipolysis, maximum TG-lipase activity was also observed with lipid droplets isolated 10 min after hormonal stimulation. The activation of lipolysis was reconstituted in vitro using purified insect PKA and TG-lipase and lipid droplets. In vitro phosphorylation of lipid droplets catalyzed by PKA enhanced the phosphorylation of Lsdp1 and the lipolytic rate of the lipase, demonstrating a prominent role PKA and protein phosphorylation on the activation of the lipid droplets. AKH-induced changes in the properties of the substrate do not promote a tight association of the lipase with the lipid droplets. It is concluded that the lipolysis in fat body adipocytes is controlled by the activation of the lipid droplet. This activation is achieved by PKA-mediated phosphorylation of the lipid droplet. Lsdp1 is the main target of PKA, suggesting that this protein is a major player in the activation of lipolysis in insects.Insects rely on lipid reserves to survive during physiological non-feeding periods or to meet the energy requirements of developing eggs, flight, and starvation. The fat body is the principal site for storage of both glycogen and lipids. The fat body synthesizes most of the proteins found in the hemolymph while also serving as the main storage site of triglycerides (TG), 1 which constitute Ͼ90% fat body lipids. Therefore, functionally, the fat body accomplishes roles that in vertebrates are carried out by both liver and adipose tissue (1).The tobacco hornworm, Manduca sexta, feeds constantly, and the content of fat body TG increases continuously until the end of the larval development. During the larval period (ϳ20 days), the content of TG in the fat body increases from a few micrograms to ϳ80 mg (2). During subsequent development, the lipid reserves are used to sustain the life of the adult insect, which feeds occasionally (2-5). Due to these metabolic features, M. sexta represents an excellent model for studying the basic mechanisms involved in either the synthesis/deposition o...

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“…The formation of LDLp in the haemolymph of an insect in response to immune challenge was first demonstrated in larvae of the greater wax moth, Galleria mellonella (Dettloff et al, 2001b). No experiments involving co-injection of AKH with microbes or immunogens were undertaken in Galleria larvae, most likely because the effect of AKH in lepidopteran larvae is to mobilise carbohydrate rather than lipid (Ziegler et al, 1990). Therefore the appearance of LDLp in response to microbial challenge is unlikely to be mediated in Galleria by the release of endogenous AKH, and this is consistent with the findings in the locust as shown in this study.…”

Section: Discussionmentioning

confidence: 99%

Induced hyperlipaemia and immune challenge in locusts

Mullen

Lightfoot

Goldsworthy

2004

Journal of Insect Physiology

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Injections of immunogens, such as β-1,3-glucan or lipopolysaccharide (LPS), bring about a marked hyperlipaemia with associated changes in lipophorins and apolipophorin-III in the haemolymph of Locusta migratoria. These changes are similar to those observed after injection of adipokinetic hormone (AKH). The possibility that endogenous AKH is released as part of the response to these immunogens is investigated using passive immunisation against AKH-I, and measurement of AKH-I titre in the haemolymph after injection of immunogens. The data presented show that, despite the similarity of the changes brought about by the presence of immunogens in the haemolymph to those brought about by AKH, there is no release of endogenous AKH after injection of laminarin or LPS. A direct effect of the immunogens on release of neutral lipids by the fat body cannot be demonstrated in vitro, and the mechanism by which hyperlipaemia is induced during immune challenge remains uncertain.

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Adipokinetic hormone controls lipid metabolism in adults and carbohydrate metabolism in larvae of Manduca sexta

Cited by 64 publications

References 17 publications

The main triglyceride-lipase from the insect fat body is an active phospholipase A1: identification and characterization

The main triglyceride-lipase from the insect fat body is an active phospholipase A1: identification and characterization

Activation of the Lipid Droplet Controls the Rate of Lipolysis of Triglycerides in the Insect Fat Body

Induced hyperlipaemia and immune challenge in locusts

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