Binding and degradation of 125I-glucagon by highly purified rat liver plasma membranes

Balage, Michèle; Grizard, Jean; Grizard, G.

doi:10.1016/0304-4165(86)90232-1

Cited by 7 publications

(4 citation statements)

References 19 publications

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“…A GR-linked protease in plasma membranes appears to be responsible for cleavages at internal and C-terminal regions of the glucagon molecule and for the generation of two fragments, glucagon-(1-13) and - (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), the former remaining tightly membrane bound (Table 1) [22,120]. This is compatible with the observation of Balage et al [123] that about 20 % of [ 125 I]iodo-A C H T U N G T R E N N U N G glucagon bound to hepatic plasma membranes was of decreased apparent molecular weight as assessed by gel filtration. Formation of this fragment was inhibited by phenylmethylsulfonyl fluoride (PMSF), but not aprotinin, soybean trypsin inhibitor, bacitracin or N-ethylmaleimide, indicating that the relevant enzymatic activity resulted from a serine protease [22,120].…”

supporting

confidence: 90%

Glucagon receptors

Authier

Desbuquois

2008

Cell. Mol. Life Sci.

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Glucagon is a pancreatic peptide hormone that, as a counterregulatory hormone for insulin, stimulates glucose release by the liver and maintains glucose homeostasis. First described as a glucagon binding entity functionally linked to adenylyl cyclase, the glucagon receptor is a member of the family B receptors within the G protein coupled superfamily of seven transmembrane-spanning receptors. During the past decade, considerable progress has been made in the identification of the molecular determinants of the glucagon receptor that are important for ligand binding and signal transduction, in the development of glucagon analogs and of nonpeptide small molecules acting as receptor antagonists, and in the characterization of the mechanisms involved in the regulation of expression of the glucagon receptor gene. In the present review, the current knowledge of glucagon receptor structure, function and expression is described, with emphasis on the metabolic fate of glucagon and on the endocytosis and cell itinerary of both ligand and receptor.

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supporting

confidence: 90%

Glucagon receptors

Authier

Desbuquois

2008

Cell. Mol. Life Sci.

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“…This enzyme requires a metal ion and low pH for optimal activity. Glucagon may, in addition, be degraded at the plasma membrane as a glucagon-degrading protease has been detected in the plasma membrane fraction [110,[143][144][145][146].…”

Section: Receptor-mediated Endocytosis and Degradation Of Insulin Andmentioning

confidence: 99%

Physiological functions of endosomal proteolysis

Berg¹,

Gjøen²,

Bakke³

1995

Biochemical Journal

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“…Studies on intact isolated hepatocytes have enabled the identification of two pathways of glucagon degradation: one chloroquine-sensitive pathway, shown to result in the cleavage of glucagon to low-molecular-mass peptides and suggested to occur in lysosomes [6]; and one chloroquine-insensilive pathway, shown to result in the removal of the three N-terminal residues of the hormone and suggested to occur in a superficial region of the hepatocyte [3]. Studies with isolated liver plasma membranes have shown that, after binding to its receptor, glucagon is processed to fragments that remain in part membrane-associated [7,8]; the Tyr'3-Leu"4 bond was identified as one major site of cleavage [9].…”

Section: Introductionmentioning

confidence: 99%

Fate of injected glucagon taken up by rat liver in vivo. Degradation of internalized ligand in the endosomal compartment

Authier

Janicot

Lederer

et al. 1990

Biochemical Journal

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The uptake and processing of glucagon into liver endosomes were studied in vivo by subcellular fractionation. After injection of [[125I]iodo-Tyr10]glucagon and [[125I]iodo-Tyr13]glucagon to rats, the uptake of radioactivity into the liver was maximum at 2 min (6% of the dose/g of tissue). On differential centrifugation, the radioactivity in the homogenate was recovered mainly in the nuclear (N), microsomal (P) and supernatant (S) fractions, with maxima at 5, 10 and 40 min, respectively; recovery of radioactivity in the mitochondrial-lysosomal (ML) fraction did not exceed 6% and was maximal at 20 min. On density-gradient centrifugation, the radioactivity associated first (2-10 min) with plasma membranes and then (10-40 min) with Golgi-endosomal (GE) fractions, with 2-5-fold and 20-150-fold enrichments respectively. Subfractionation of the GE fractions showed that, unlike the Golgi marker galactosyltransferase, the radioactivity was density-shifted by diaminobenzidine cytochemistry. Subfractionation of the ML fraction isolated at 40 min showed that more than half of the radioactivity was recovered at lower densities than the lysosomal marker acid phosphatase. Throughout the time of study, the [125I]iodoglucagon associated with the P, PM and GE fractions remained at least 80-90% trichloroacetic acid (TCA)-precipitable, whereas that associated with other fractions, especially the S fraction, became progressively TCA-soluble. On gel filtration and h.p.l.c., the small amount of degraded [125I]iodoglucagon associated with GE fractions was found to consist of monoiodotyrosine. Chloroquine treatment of [125I]iodoglucagon-injected rats caused a moderate but significant increase in the late recovery of radioactivity in the ML, P and GE fractions, but had little effect on the association of the ML radioactivity with acid-phosphatase-containing structures. Chloroquine treatment also led to a paradoxical decrease in the TCA-precipitability of the radioactivity associated with the P and GE fractions. Upon h.p.l.c. analysis of GE extracts of chloroquine-treated rats, at least four degradation products less hydrophobic than intact [125I]iodoglucagon were identified. Radio-sequence analysis of four of these products revealed three cleavages, affecting bonds Ser2-Gln3, Thr5-Phe6 and Phe6-Thr7. When GE fractions containing internalized [125I]iodoglucagon were incubated in iso-osmotic KCl at 30 degrees C, a rapid generation of TCA-soluble products was observed, with a maximum at pH 4. We conclude that endosomes are a major site at which internalized glucagon is degraded, endosomal acidification being required for optimum degradation.

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Binding and degradation of 125I-glucagon by highly purified rat liver plasma membranes

Cited by 7 publications

References 19 publications

Glucagon receptors

Glucagon receptors

Physiological functions of endosomal proteolysis

Fate of injected glucagon taken up by rat liver in vivo. Degradation of internalized ligand in the endosomal compartment

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