Phospholipid class and fatty acid composition of Golgi apparatus isolated from rat liver and comparison with other cell fractions

Tw, Keenan; Dj, Morré

doi:10.1021/bi00803a003

Cited by 284 publications

(112 citation statements)

References 32 publications

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“…As already shown (46), this fraction represents primarily the light components of the Golgi complex and as such it cannot be compared to the usual smooth microsomal fraction isolated from liver homogenates . It is in part similar to Golgi-rich fractions isolated from rat (47,48) and ox (49) liver, and to the "smooth II fraction" obtained by Dallner (29) . The intracellular source of the latter fraction is unknown .…”

Section: Washing Of Pancreatic Membranes With Albuminsupporting

confidence: 83%

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Meldolesi

Jamieson

Palade

1971

The Journal of Cell Biology

141

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1 3 0The lipid composition of rough and smooth microsomal membranes, zymogen granule membranes, and a plasmalemmal fraction from the guinea pig pancreatic exocrine cell has been determined . As a group, membranes of the smooth variety (i .e ., smooth microsomes, zymogen granule membranes, and the plasmalemma) were similar in their content of phospholipids, cholesterol and neutral lipids, and in the ratio of total lipids to membrane proteins . In contrast, rough microsomal membranes contained much less sphingomyelin and cholesterol and possessed a smaller lipid/protein ratio . All membrane fractions were unusually high in their content of lysolecithin (up to _~20% of the total phospholipids) and of neutral lipids, especially fatty acids . The lysolecithin content was shown to be due to the hydrolysis of membrane lecithin by pancreatic lipase ; the fatty acids, liberated by the action of lipase on endogenous triglyceride stores, are apparently scavenged by the membranes from the suspending media . Similar artifactually high levels of lysolecithin and fatty acids were noted in hepatic microsomes incubated with pancreatic postmicrosomal supernatant . E 600, an inhibitor of lipase, largely prevented the appearance of lysolecithin and fatty acids in pancreatic microsomes and in liver microsomes treated with pancreatic supernatant .In the first article of this series, we have described the separation of membrane subfractions from rough microsome-, smooth microsome-, and zymogen granule fractions isolated from homogenates of guinea pig pancreas . We have also shown that a cell membrane fraction can be obtained from the same source (1) .These fractions represent membrane-bounded compartments which are involved in the synthesis, segregation, intracellular transport, and discharge of secretory proteins . In an attempt to understand how the membranes of these compartments interact with one another during the secretory process, we have investigated their chemical composition and enzyme activities . In this paper the lipid composition of the membranes is described .At the onset of this study, we anticipated that a small fraction of the digestive enzymes stored in the gland, particularly in zymogen granules and in the duct system, could be released during tissue homogenization and fractionation and thereupon cause artifactual degradation and alteration of membrane components . In this respect, it has been reported that pancreatic lipase is active in the cold (2) and that at least some proteases may become activated during cell fractionation (3) . Indeed, our studies showed that released lipolytic enzymes extensively affect the lipid composition of the isolated membranes . These alterations have been evaluated and the data on membrane lipids have been corrected accordingly .

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Section: Washing Of Pancreatic Membranes With Albuminsupporting

confidence: 83%

Composition of Cellular Membranes in the Pancreas of the Guinea Pig

Meldolesi

Jamieson

Palade

1971

The Journal of Cell Biology

141

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“…Cytomembranes of the "thick" variety (80-100 A) which have potential access to the extracellular milieu are rich in cholesterol and include plasma membrane, lysosomal membrane, and secretion granules (1-10). In contrast, "thin" membranes (40-70 A) such as endoplasmic reticulum, mitochondria, and nuclear envelope are poor in cholesterol, whereas Golgi membranes are intermediate in size and cholesterol content (5,11,12).Although there is an extensive literature on cholesterol metabolism of the whole organism (13-16), our knowledge of the cellular level is fragmentary. Exceptions are the well-documented studies first described by Hagerman and Gould (17) demonstrating cholesterol exchange from plasma lipoproteins to the membrane of erythrocytes.…”

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confidence: 99%

mentioning

confidence: 99%

Cholesterol Metabolism in the Macrophage

Werb

Cohn

1971

The Journal of Experimental Medicine

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Cholesterol is a constituent of all mammalian cells and serves as a structural unit of membranes. Cytomembranes of the "thick" variety (80-100 A) which have potential access to the extracellular milieu are rich in cholesterol and include plasma membrane, lysosomal membrane, and secretion granules (1-10). In contrast, "thin" membranes (40-70 A) such as endoplasmic reticulum, mitochondria, and nuclear envelope are poor in cholesterol, whereas Golgi membranes are intermediate in size and cholesterol content (5,11,12).Although there is an extensive literature on cholesterol metabolism of the whole organism (13-16), our knowledge of the cellular level is fragmentary. Exceptions are the well-documented studies first described by Hagerman and Gould (17) demonstrating cholesterol exchange from plasma lipoproteins to the membrane of erythrocytes. No net change in cholesterol content of red cell takes place and cholesterol ester (CE) 1 exchange is very limited. Recently, the de novo biosynthesis of cholesterol by cultured eukaryotic cells has been shown (18-20) although its conversion to metabolites other than its esters has not been demonstrated (19,21,22).We have chosen to examine the metabolism of cholesterol in homogeneous populations of macrophages. This was prompted by the physiological role of this cell in the processing of chylomicrons and effete erythrocytes (23)(24)(25) and its association with a number of pathological events in which lipid storage takes place (26)(27)(28)(29)(30). In addition, macrophages exhibit striking endocytic activity in which the flow and turnover of cholesterol-rich membranes might be examined.In this article we will describe the content and subcellular distribution of macrophage cholesterol, the factors controlling exchange, and its biosynthesis under defined cultural conditions.

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“…Most notably, glycosphingolipids, sphingomyelin (SM), disaturated phospholipids and cholesterol are tenfold enriched in the plasma membrane as compared with the endoplasmic reticulum (ER) 1 . The ER membrane bilayer is symmetrical owing to the presence of a nonenergy-requiring, ultrarapid, translocase (A. Herrmann, Berlin, Germany) for which first purification steps were presented 2 .…”

Section: Translocatorsmentioning

confidence: 99%

“…Phospholipids synthesized in the endoplasmic reticulum (ER) are distributed symmetrically across the bilayer (green) due to a bidirectional flippase (1). The ER is connected with the Golgi via anterograde and retrograde vesicular pathways (arrows).…”

Section: Figurementioning

confidence: 99%