Uptake of gold- and [3H]cholesteryl linoleate-labeled human low density lipoprotein by cultured rat granulosa cells: cellular mechanisms involved in lipoprotein metabolism and their importance to steroidogenesis.

Paavola, Laurie G.; Strauss, Jerome F.; Boyd, Charles O.; Nestler, John E.

doi:10.1083/jcb.100.4.1235

Cited by 41 publications

(17 citation statements)

References 36 publications

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“…asialoglycoproteins) or other cells and for LDL taken up by fibroblasts or by luteinized ovarian cells (38)(39)(40)(41)(42)(43). Briefly, the steps of these processes are the following ( Fig.…”

Section: Intracellular Pathway Of Lipoproteinmentioning

confidence: 99%

Hepatocytic lipoprotein receptors and intracellular lipoprotein catabolism

1988

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Hepatocytes, as the major site of synthesis and terminal catabolism of plasma lipoproteins, exert the major regulatory influence on the concentration of atherogenic lipoproteins in blood plasma and may thereby influence the rate of atherogenesis. The LDL receptor on the microvillous sinusoidal surface of hepatocytes mediates the catabolism of remnants of triglyceride-rich lipoproteins and LDL. Binding of VLDL remnants to the receptor, mediated by apo E, is of very high affinity and presumably multivalent, whereas binding of LDL, mediated by apo B-100, is monovalent and of lower affinity, accounting for the much longer residence time of the latter in the blood. The magnitude of the influx of lipoprotein particles into hepatocytic endosomal compartments dwarfs that of other macromolecules undergoing receptor-mediated endocytosis and terminal catabolism in lysosomes of these cells. The intracellular compartments and processing steps in hepatocytic lipoprotein uptake and degradation are essentially the same as those described for other ligands in the liver and other cells. Receptors with bound lipoproteins migrate into coated pits which become coated vesicles. These vesicles uncoat and fuse to form CURL vesicles and tubules near the cell surface where most receptors are recycled, presumably via receptor-rich appendages that become separated from the vesicles. CURL vesicles become mature MVBs as they migrate to the Golgi/bile canalicular pole of hepatocytes, where they fuse with putative Golgi-derived primary lysosomes and are transformed into heterophagic secondary lysosomes. MVBs also contain a receptor-rich appendage that may recycle some receptors directly to the cell surface or through adjacent Golgi compartments. Dilated ends of trans-Golgi cisternae contain nascent VLDL undergoing packaging for secretion following their synthesis and assembly in the endoplasmic reticulum. Because these "forming secretory vesicles" resemble remnant-filled MVBs, occur in a similar location in the Golgi area of hepatocytes and coisolate in centrifugal fractions of liver homogenates, there has been considerable confusion about the identity of these compartments. With the aid of specific endocytic and exocytic markers, highly purified and morphologically intact endosomal and Golgi compartments can now be obtained from rat liver homogenates. The availability of these and similar fractions of defined purity should facilitate investigation of the hepatocytic processing of endocytosed and secreted macromolecules. Although chylomicron remnants are also taken up by receptor-mediated endocytosis, the nature of the hepatocytic remnant receptor remains elusive.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Intracellular Pathway Of Lipoproteinmentioning

confidence: 99%

Hepatocytic lipoprotein receptors and intracellular lipoprotein catabolism

1988

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“…After standing on ice for 3 h, the sample was centrifuged and the cell pellet was washed three times with cold growth medium adjusted to pH 7.0. Fixed cells were washed with 0.1 M sodium cacodylate (pH 7.4) containing 5% sucrose, mordanted in 1 % tannic acid to improve membrane visibility, stained en bloc with saturated aqueous uranyl acetate, dehydrated in graded ethanols, and embedded in low viscosity resin as detailed earlier (26). Thin sections were stained with uranyl acetate (3-5 min) and lead citrate (1-2 min) and viewed in a JOEL 100B electron microscope.…”

Section: Electron Microscopymentioning

confidence: 99%

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Jk¹,

Co²,

Lg³

1991

Plant Physiol.

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The origin of thylakoid membranes was studied in Chlamydomonas reinhardtii y-1 cells during greening at 380C. Previous studies showed that, when dark-grown cells are exposed to light under these conditions, the initial rates of accumulation of chlorophyll and the chlorophyll a/b-binding proteins in membranes are maximal (MA Maloney JK Hoober, DB Marks [1989] Plant Physiol 91: 1100-1106; JK Hoober MA Maloney, LR Asbury, DB Marks [1990] Plant Physiol 92: 419-426). As shown in this paper, photosystem 11 activity, which was nearly absent in dark-grown cells, also increased at a linear rate in parallel with chlorophyll. As compared with those made at 250C, photosystem 11 units assembled during greening at 380C were photochemically more efficient, as judged by saturation at a lower fluence of light and a negligible loss of excitation energy as fluorescence. Electron microscopy of cells in light for 5 or 15 minutes at 380C showed that these initial, functional thylakoid membranes developed in association with the chloroplast envelope.

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“…2A disappeared totally from the plasma membranes but instead became detectable inside the small vesicles that exhibited morphological characteristics similar to those of coated vesicles. After incubation at 37°C for 10 min, reaction products were visualized in several vesicles whose structures were similar in appearance either to multivesicular bodies that were claimed to be a prelysosomal compartment (5,12,15) or to membrane-bound vesicles characteristic of secondary lysosomes (3,20). Thus, these results strongly suggest that within 10 min after ligand binding, the acetyl-LDL receptors cluster with each other into the coated pits, through which they were internalized and transferred via coated vesicles at least to prelysosomal compartments.…”

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confidence: 99%

Endocytic pathway of acetylated low-density lipoprotein in rat peritoneal macrophages.

Fukuda

Takahashi

Horiuchi

1986

Acta Histochem. Cytochem

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It has been generally admitted that cholesteryl ester-loaded foam cells, one of the major cell components of atherosclerotic lesions, are derived from macrophages or smooth muscle cells and that low-density lipoprotein (LDL) is the major atherogenic lipoprotein (8,17) . The discovery of the LDL pathway by Goldstein and Brown not only contributes to our understanding of cholesterol metabolism but also suggests the importance of a receptor-mediated endocytic mechanism in biological systems. However, endocytosis of LDL via this pathway by most cultured cells does not lead to substantial intracellular cholesterol accumulation and this receptor is poorly expressed by macrophages or macrophage-derived cells. Moreover, atheromatous plaques comprised of typical foam cells develop in the patients genetally devoid of this receptor. A subsequent discovery that incubation of cultured macrophages with acetylated LDL (acetyl-LDL) resulted in massive intracellular accumulation of cholesteryl esters has shed light on this dilemma (9). The scavenger function of macrophages or macrophage-derived cells for chemically modified proteins has since been intensively studied from its potential link to atherosclerosis (4).These studies have suggested that the endocytosis of LDL preparations chemically modified by acetylation, acetoacetylation, malondialdehyde treatment or modified by in vitro incubation with endothelial cells is mediated by a scavenger receptor termed the acetyl-LDL receptor (7,9,10,22). This has been demonstrated in macrophages or macrophage-derived cells, such as mouse peritoneal macrophages, human monocytes or sinusoidal liver cells (2,7,9,11,14,22).In the present communication, morphological approaches have been attempted to reveal the endocytic pathway for acetyl-LDL and subsequent foam cell formation in rat peritoneal macrophages. The results are presented with discussions on the pathophysiological significance of the scavenger function in cholesterol metabolism of macrophages or macrophage-derived cells. RESULTS AND DISCUSSIONIncubation of rat peritoneal macrophages with 50 ug/ml of native unmodified human LDL for 48 hr at 37°C did not change their morphology (Fig. 1B). On the other hand, upon incubation with acetyl-LDL under the same conditions, many lipid vacuoles appeared in the cytoplasm, exhibiting typical foam cells (Fig. 1A). Further biochemical approaches using either 125I-LDL or 125I-acetyl-LDL also showed the contrasting behavior of these two radiolabeled ligands in the interaction with macrophages; 125I-LDL did not display significant binding to the cells nor 145

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Uptake of gold- and [3H]cholesteryl linoleate-labeled human low density lipoprotein by cultured rat granulosa cells: cellular mechanisms involved in lipoprotein metabolism and their importance to steroidogenesis.

Cited by 41 publications

References 36 publications

Hepatocytic lipoprotein receptors and intracellular lipoprotein catabolism

Hepatocytic lipoprotein receptors and intracellular lipoprotein catabolism

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C

Endocytic pathway of acetylated low-density lipoprotein in rat peritoneal macrophages.

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