Isolation and characterization of a liver plasma membrane fraction enriched in glucagon-sensitive adenylate cyclase

Swislocki, Norbert I.; Tierney, John; Essner, Edward

doi:10.1016/0003-9861(76)90347-7

Cited by 15 publications

(7 citation statements)

References 17 publications

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“…For comparison, purified preparations were made of the two well characterized enzymes which degrade insulin: insulin-glucagon protease from rat skeletal muscle (9,17) and glutathione insulin transhydrogenase from rat liver (18). These enzyme preparations were electrophoresed and assayed under conditions identical to those used for the membrane preparations.…”

Section: Polyacrylamide Gel Electrophoresis Of Solubilized Membrane Pmentioning

confidence: 99%

“…Three membrane fractions are obtained, at sucrose densities of 1.23, 1.16, and 1.03. The peak 2 (density, 1.16) membrane fraction possesses the adenylate cyclase activity most responsive to hormonal stimulation (9). This fraction will be referred to hereafter as the purified membrane preparation.…”

Section: Membrane Preparationmentioning

confidence: 99%

“…Liver cell membranes were prepared by the Swislocki et al (9) modification of the method of Neville (10). In this procedure, partially purified membranes obtained by the Neville method INSULIN DEGRADATION BY LIVER MEMBRANES 1759 (step 11) are further purified by centrifugation at 35,000 X g for 20 min in SW 25.1 tubes containing 4.1 ml 50% sucrose, 10 ml 37% sucrose, and 10 ml 10% sucrose.…”

Section: Membrane Preparationmentioning

confidence: 99%

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Insulin Degradation by Liver Cell Membranes*

Duckworth

1979

Endocrinology

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Liver cell membranes actively degrade insulin, but the mechanism for this process has not been established. Exposure of [ 125 I]iodoinsulin for various times to a liver cell membrane preparation enriched in blood sinusoidal surfaces resulted in the generation of labeled products of varying sizes.Separation of these products on a molecular sieve column demonstrated a progressive decrease in 125 I-labeled material eluting in the insulin peak and an increase in both larger and smaller molecular weight materials. The latter could be separated into at least three distinct peaks. In addition, the material eluting in the insulin peak had a decreased immunoprecipitability, suggesting that this peak was also heterogeneous. The l25 I-labeled material extracted from the membranes eluted from the molecular sieve column predominantly in the void volume and in the insulin peak. There was an increase with time in the larger molecular weight fraction.The liver membrane insulin-degrading activity was characterized by polyacrylamide gel electrophoresis after solubilization by Triton X-100. Only one area of insulin-degrading activity was found. This activity had a mobility identical with the mobility of purified insulin protease and distinctly different from that of purified glutathione insulin transhydrogenase. Furthermore, no glutathione insulin transhydrogenase activity could be demonstrated using an assay specific for that enzyme. Thus, the insulindegrading activity of liver cell membranes appears to be due to the proteolytic enzyme insulin protease. (Endocrinology 104: 1758, 1979)

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Section: Polyacrylamide Gel Electrophoresis Of Solubilized Membrane Pmentioning

confidence: 99%

Section: Membrane Preparationmentioning

confidence: 99%

Section: Membrane Preparationmentioning

confidence: 99%

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Insulin Degradation by Liver Cell Membranes*

Duckworth

1979

Endocrinology

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“…Purified rat liver plasma membranes were isolated as described earlier (3). Adenylate cyclase was assayed as described previously (4).…”

Section: Methodsmentioning

confidence: 99%

A Solubilized and Active Adenylate Cyclase Lipidated with Native Annular Lipids

Scotto¹,

Swislocki²

1982

Biophysical Journal

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“…In liver, as well as in most other tissues examined, adenylyl cyclase is associated almost exclusively with the particulate fraction and is considered to be localized mainly in plasma membranes (79,145,149,194). Adenylyl cyclase is situated on the inner surface of plasma membranes (145,161) and is referred to as the catalytic component; other components of the adenylyl cyclase system include: the regulatory (discriminatory or receptor) component, located on the outer surface of the plasma membrane, and the coupling (transducer) component within the membrane, interposed between the regulatory and catalytic subunits.…”

Section: Metabolism Of Cyclic Nucleotides Synthesis Adenylyl Cyclase mentioning

confidence: 99%

Regulation of Cyclic AMP and Cyclic GMP in Morris Hepatomas and Liver

Hickie

1978

Morris Hepatomas

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SUMMARYStudies on the regulation of tissue levels and action of adenosine 3':5'-monophosphate (cyclic AMP) and cyclic guanosine 3':5'-monophosphate (cyclic GMP) in Morris hepatomas and liver have been reviewed. Though the data is incomplete in some areas, the following generalizations can be made. A prominent difference between Morris hepatomas and normal liver, in relation to cyclic AMP formation, is the decreased responsiveness of tumor adenylyl cyclase to glucagon. This characteristic is most marked in rapidly growing hepatomas and appears to be associated with diminished plasma membrane binding of glucagon; regenerating liver and fetal liver resemble hepatomas in their responsiveness to glucagon. The responsiveness of adenylyl cyclase to epinephrine is, in contrast, generally enhanced in hepatomas as well as in regenerating and fetal liver. Marked increases in particulate guanylyl cyclase activities, relative to corresponding soluble activities, are seen consistently in Morris hepatomas and in regenerating and fetal liver; in the latter tissues, increases in plasma membrane guanylyl cyclase activities can be correlated with increased proliferative activity. Although the total cyclic AMP phosphodiesterase activities are significantly reduced in all Morris hepatomas examined, the activities of the high affinity (low Km) cyclic AMP phosphodiesterase in plasma membranes from some Morris hepatomas are higher than those of normal liver. The degradation of cyclic GMP by Morris hepatomas is also impaired, most notably in the particulate fractions. In regenerating and fetal liver the activities of cyclic AMP and cyclic GMP phosphodiesterases are, in contrast, not changed appreciably. The ratios of cyclic GMP levels, relative to cyclic AMP, tend to be higher in Morris hepatomas than in normal liver. Though these ratios are highest in rapidly growing hepatomas, the correlation between cyclic nucleotide levels and tumor growth rate is not strong. The correlation between cyclic GMP/cyclic AMP ratios and hepatocyte proliferation is controversial at this time; the most recent studies on regenerating liver suggest that these ratios are increased prior to the proliferative phase. Only a few studies have been carried out on cyclic nucleotide binding proteins and kinases. These studies indicate that: cytosols from rapidly growing hepatomas have a reduced ability to bind cyclic AMP with increased (?) binding of cyclic GMP; there is a positive correlation between cyclic AMP binding and tumor sensitivity to growth inhibition by dibutyryl cyclic AMP; cytosol fractions from rapidly growing hepatomas generally have reduced cyclic AMP dependent protein kinase activities and increased endogenous (cyclic AMP independent) kinase activities.

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Isolation and characterization of a liver plasma membrane fraction enriched in glucagon-sensitive adenylate cyclase

Cited by 15 publications

References 17 publications

Insulin Degradation by Liver Cell Membranes*

Insulin Degradation by Liver Cell Membranes*

A Solubilized and Active Adenylate Cyclase Lipidated with Native Annular Lipids

Regulation of Cyclic AMP and Cyclic GMP in Morris Hepatomas and Liver

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