signal transduction of adipokinetic hormones involves Ca2+ fluxes and depends on extracellular Ca2+ to potentiate cAMP-induced activation of glycogen phosphorylase

Vroemen, Simon F.

doi:10.1016/0143-4160(95)90092-6

Cited by 35 publications

(16 citation statements)

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“…The need for extracellular Ca 2+ to enable activation by Pea-HTH-I and Pea-HTH-II of phosphorylase in dispersed trophocytes has been convincingly demonstrated by the action of EGTA, which maintains [Ca 2+ ] o near zero. A similar requirement for extracellular Ca 2+ during hormonal activation of phosphorylase in intact fat body has been shown for P. americana by McClure and Steele (1981), for Locusta migratoria by Vroemen et al, (1995), and for Blaberus discoidalis by Park and Keeley (1995). These results are consistent with the finding that trehalose production by P. americana fat body in vitro Fig.…”

Section: Discussionsupporting

confidence: 89%

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Steele

Ireland

1999

Arch. Insect Biochem.

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This study is an investigation of the temporal relationship between transmembrane Ca(2+) fluxes, and glycogen phosphorylase activation in dispersed trophocytes from the fat body of the cockroach, Periplaneta americana. Phosphorylase is maximally activated within 5 min after treating the trophocytes with either of the hypertrehalosemic hormones, Pea-HTH-I and Pea-HTH-II. Activation caused by Pea-HTH-II is sustained for a longer period than that produced by Pea-HTH-I. Chelation of extracellular Ca(2+) with EGTA blocks the activation of phosphorylase by HTH. Similarly, chelation of intracellular Ca(2+) with Quin 2 greatly diminishes the phosphorylase activating effect of both HTHs. The data support the view that an increase in the intracellular Ca(2+ )concentration is required for the activation of phosphorylase and that extracellular Ca(2+) is an essential, although not necessarily sole, source of Ca(2+) for this purpose. Using (45)Ca(2+) to trace the movement of Ca(2+) following a challenge with either Pea-HTH-I or -II, it was shown that (45)Ca(2+)influx nearly doubled during the first 30 s. At this time, the trophocytes begin to expel Ca(2+) at a rate higher than that of untreated cells and this state persists for approximately 4 min. The Ca(2+) fluxes are consistent with its postulated role in the activation of phosphorylase. Arch.

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Section: Discussionsupporting

confidence: 89%

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Steele

Ireland

1999

Arch. Insect Biochem.

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“…3 InsP 1 was by far the most abundant isomer, but for AKH-I and AKH-III, the rises in InsP 3 after 1 minute were disproportionally high. AKH-II did not enhance InsP 3 . By contrast to AKH-I and AKH-II, InsP 3 levels induced by AKH-III were still elevated after 15 minutes, suggesting that this hormone has a more prolonged effect on Ca 2+ signaling.…”

Section: Formation Of Inositol Phosphates By the Adipokinetic Hormonesmentioning

confidence: 85%

“…This is quite surprising, as Ca 2+ fluxes enhanced by all three AKHs occur immediately after addition of the hormone. 3 InsP 1 was by far the most abundant isomer, but for AKH‐I and AKH‐III, the rises in InsP 3 after 1 minute were disproportionally high. AKH‐II did not enhance InsP 3 .…”

Section: Formation Of Inositol Phosphates By the Adipokinetic Hormonesmentioning

confidence: 91%

“…2 The AKHs also induce influx and efflux of Ca 2+ into/from the fat body, probably resulting in an increase in intracellular Ca 2+ levels. 3 Both cAMP and Ca 2+ can activate GPh, although maximal activation only occurs in the presence of both messengers. The fact that the AKH effect on Ca 2+ influx can be mimicked by thapsigargin suggests that capacitative Ca 2+ entry occurs.…”

mentioning

confidence: 99%

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Adipokinetic Hormone Signaling: Role of Inositol Phosphates^a

Vroemen

Marrewijk

Horst

1998

Annals of the New York Academy of Sciences

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“…The most important target tissue for the AKHs is the fat body, in which they stimulate the hormone-dependent triacylglycerol lipase and glycogen phosphorylase (13), though with different potencies (14). Since physiological responses of AKHs in the fat body include an increase in cAMP level (15) as well as stimulation of phosphoinositide turnover (16) and depend on intra-and/or extracellular calcium ions (17)(18)(19), it is most likely that-like other receptors for peptide hormones-also the AKH receptor or receptors are linked to G proteins for their intracellular responses (15). The titer of the AKHs in the hemolymph is very low (20,21), and their hydrophobic nature suggests their transport to be in association with specific transport or carrier molecules or with the lipid-transporting lipophorins, though this has never been postulated.…”

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confidence: 99%

Locust adipokinetic hormones: carrier-independent transport and differential inactivation at physiological concentrations during rest and flight.

Oudejans

Vroemen²,

Jansen³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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Since concomitant release of structurally related peptide hormones with apparently similar functions seems to be a general concept in endocrinology, we have studied the dynamics of the lifetime of the three known adipokinetic hormones (AKHs) of the migratory locust, which control flight-directed mobilization of carbohydrate and lipid from fat body stores. Although the structure of the first member of the AKHs has been known for 20 years, until now, reliable data on their inactivation and removal from the hemolymph are lacking, because measurement requires AKHs with high specific radioactivity. Employing tritiated AKHs with high specific radioactivity, obtained by catalytic reduction with tritium gas of the dehydroLeu2 analogues of the AKHs synthesized by the solid-phase procedure, studies with physiological doses of as low as 1.0 pmol per locust could be conducted. The AKHs appear to be transported in the hemolymph in their free forms and not associated with a carrier protein, despite their strong hydrophobicity. Application of AKHs in their free form in in vivo and in vitro studies therefore now has been justified. We have studied the degradation of the three AKHs during rest and flight. The first cleavage step by an endopeptidase is crucial, since the resulting degradation -products lack any adipokinetic activity. Half-lives for AKH-I, -II and -m were 51, 40, and 5 min, respectively, for rest conditions and 35, 37, and 3 min, respectively, during flight.

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signal transduction of adipokinetic hormones involves Ca2+ fluxes and depends on extracellular Ca2+ to potentiate cAMP-induced activation of glycogen phosphorylase

Cited by 35 publications

References 27 publications

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Adipokinetic Hormone Signaling: Role of Inositol Phosphates^a

Locust adipokinetic hormones: carrier-independent transport and differential inactivation at physiological concentrations during rest and flight.

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signal transduction of adipokinetic hormones involves Ca2+ fluxes and depends on extracellular Ca2+ to potentiate cAMP-induced activation of glycogen phosphorylase

Cited by 35 publications

References 27 publications

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans‐membrane calcium flux

Adipokinetic Hormone Signaling: Role of Inositol Phosphatesa

Locust adipokinetic hormones: carrier-independent transport and differential inactivation at physiological concentrations during rest and flight.

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Adipokinetic Hormone Signaling: Role of Inositol Phosphates^a