Concentration of intracellular hepatic apolipoprotein E in Golgi apparatus saccular distensions and endosomes.

Dahan, Sophie; Ahluwalia, Jatinder; Wong, Laurence; Posner, Barry I.; Bergeron, John J.M.

doi:10.1083/jcb.127.6.1859

Cited by 78 publications

(68 citation statements)

References 62 publications

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“…6D). These findings are consistent with the rat liver results of Bergeron et al (33) and with a negative-staining immunoelectron microscopic procedure in which vesicles were left intact. ER-derived vesicles had 2.5 times more signal for (exterior) apoB than Golgi-derived vesicles prepared under basal (i.e.…”

Section: Immunoelectron Microscopic Analysis Of Mca Cells Indicates Psupporting

confidence: 92%

Golgi-associated Maturation of Very Low Density Lipoproteins Involves Conformational Changes in Apolipoprotein B, but Is Not Dependent on Apolipoprotein E

Gusarova

Seo

Sullivan

et al. 2007

Journal of Biological Chemistry

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The major protein component in secreted very low density lipoproteins (VLDL) is apoB, and it is established that these particles can reach sizes approaching 100 nm. We previously employed a cell-free system to investigate the nature of the vesicles in which this large cargo exits the endoplasmic reticulum (ER) (Gusarova, V., Brodsky, J. L., and Fisher, E. A. (2003) J. Biol. Chem. 278, 48051-48058). We found that apoB-containing lipoproteins exit the ER as dense lipid-protein complexes regardless of the final sizes of the particles and that further expansion occurs via post-ER lipidation. Here, we focused on maturation in the Golgi apparatus. In three separate approaches, we found that VLDL maturation (as assessed by changes in buoyant density) was associated with conformational changes in apoB. In addition, as the size of VLDL expanded, apoE concentrated in a subclass of Golgi microsomes or Golgiderived vesicles that co-migrated with apoB-containing microsomes or vesicles, respectively. A relationship between apoB and apoE was further confirmed in co-localization studies by immunoelectron microscopy. These combined results are consistent with previous suggestions that apoE is required for VLDL maturation. To our surprise, however, we observed robust secretion of mature VLDL when apoE synthesis was inhibited in either rat hepatoma cells or apoE ؊/؊ mouse primary hepatocytes. We conclude that VLDL maturation in the Golgi involves apoB conformational changes and that the expansion of the lipoprotein does not require apoE; rather, the increase in VLDL surface area favors apoE binding. Very low density lipoproteins (VLDL)2 transport endogenously synthesized lipids, particularly cholesteryl esters and triglyceride, from the liver to peripheral tissues (for a recent review, see Ref. 1). VLDL assembly is a complex process that consists of at least two steps. In the first step, during its translocation across the endoplasmic reticulum (ER) membrane, nascent apolipoprotein B100 (apoB) associates with lipids provided by microsomal triglyceride transfer protein. This results in the formation of incompletely lipidated "primordial" pre-VLDL particles. In the second step, additional lipid (primarily triglyceride) and other apolipoproteins (e.g. apoE) are added, resulting in the formation of mature, fully lipidated VLDL particles (2).Although it is established that the first step of VLDL assembly occurs in the ER, the location of the additional step(s) during VLDL maturation is less clear. For example, a number of studies have suggested that the ER is the final site of VLDL maturation (e.g. Refs. 3-6), whereas others have implicated the Golgi complex as a second site of maturation (e.g. Refs. 7-12). To better distinguish between these models, we previously employed a cell-free system in which the budding of ER-derived, apoB-containing vesicles was reconstituted (13). In addition to showing that the transport of apoB from the ER is dependent on Sar1, a required factor for COPII secretory vesicle formation, we obtained preliminar...

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Section: Immunoelectron Microscopic Analysis Of Mca Cells Indicates Psupporting

confidence: 92%

Golgi-associated Maturation of Very Low Density Lipoproteins Involves Conformational Changes in Apolipoprotein B, but Is Not Dependent on Apolipoprotein E

Gusarova

Seo

Sullivan

et al. 2007

Journal of Biological Chemistry

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“…5B). This supports earlier morphological studies showing the concentration of biosynthetic material as it progresses through the secretory pathway, with the highest concentration seen in the interface between the ER and the Golgi apparatus, and with little or no further concentration across the Golgi stack (Dahan et al 1994;Martinez-Menarguez et al 1999;Oprins et al 2001). There are striking examples of cargo condensation, however, also in the Golgi stack.…”

Section: Protein Classification and Lessons Learned In The Golgi Appasupporting

confidence: 90%

Cell Biology of the Endoplasmic Reticulum and the Golgi Apparatus through Proteomics

Smirle

Jain

et al. 2013

Cold Spring Harbor Perspectives in Biology

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“…7). The second line of evidence comes from experiments in which cryosections of rat liver were labeled with antibodies to RSA and ApoE (Dahan et al, 1994). Both of these cargo molecules were detected throughout Golgi cisternae but not in COP I vesicles, consistent with the much lower density of RSA in isolated vesicles compared with starting membranes (Table 1).…”

Section: Discussionmentioning

confidence: 85%

Sorting by COP I-coated vesicles under interphase and mitotic conditions.

Sonnichsen

Watson

Clausen

et al. 1996

The Journal of Cell Biology

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Abstract. COP I-coated vesicles were analyzed for their content of resident Golgi enzymes (N-acetylgalactosaminyltransferase; N-acetylglucosaminyltransferase I; mannosidase II; galactosyltransferase), cargo (rat serum albumin; polyimmunoglobulin receptor), and recycling proteins (-KDEL receptor; ERGIC-53/p58) using biochemical and morphological techniques. The levels of these proteins were similar when the vesicles were prepared under interphase or mitotic conditions showing that sorting was unaffected. The average density relative to starting membranes for resident enzymes (14-30%), cargo (16-23%), and recycling proteins (81-125%) provides clues to the function of COP I vesicles in transport through the Golgi apparatus.T HE Golgi apparatus in mammalian cells has a unique architecture comprising a stack of flattened cisternae bounded on one side by the cis-Golgi network (CGN) 1 and on the other by the trans-Golgi network (TGN) (Rambourg and Clermont, 1990). The CGN is the entry point for the entire output of proteins synthesized and assembled in the ER (Huttner and Tooze, 1989). Cargo proteins may complete their folding in the CGN, and once assembled (Hammond and Helenius, 1994;Tatu et al., 1995), are transported through the stack in a discontinuous process (Rothman, 1994). Movement from cisterna to cisterna is often accompanied by sequential modifications to bound oligosaccharides, mediated by resident Golgi enzymes (Kornfeld and Kornfeld, 1985;Roth, 1987). Once they reach the TGN, cargo molecules are separated, packaged, and sent to their correct destination (Griffiths and Simons, 1986).Resident Golgi enzymes are thought to share the same pathway as cargo proteins up to the point where they reside and are then prevented from further forward movement. This reflects either their incorporation into heterooligomeric complexes too large for further transport (Nilsson et al., 1994) or a gradient of bilayer thickness that halts further transport once the length of the enzyme's spanning Address all correspondence to Dr. Graham Warren, Cell Biology Laboratory, Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A, 3PX, United Kingdom. Tel.: 0171 269 3561. Fax: 0171 269 3417. E-mail: g.warren@europa.lif.icnet.uk 1. Abbreviations used in this paper: CGN, cis-Golgi network; ERGIC, endoplasmic reticulum-Golgi intermediate compartment; GalNAcT, GAIT, 131, Mann II, cd,6-mannosidase I1; NAGT I, 13-1,2-N-acetylglucosaminyltransferase I; plgR, polymeric immunoglobulin receptor; RSA, rat serum albumin. domain matches that of the bilayer (Munro, 1995a,b). These models are not mutually exclusive and both may operate to ensure residence in particular cisternae (Pelham and Munro, 1993).Resident proteins of the ER are retained by less wellcharacterized mechanisms, but many are equipped with a signal that returns them to the ER should they inadvertently leave (Pelham, 1995). This retrograde pathway recognizes two types of retrieval signal. The first is -KDEL found at the COOH terminus of many soluble ER proteins (Munro ...

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Concentration of intracellular hepatic apolipoprotein E in Golgi apparatus saccular distensions and endosomes.

Cited by 78 publications

References 62 publications

Golgi-associated Maturation of Very Low Density Lipoproteins Involves Conformational Changes in Apolipoprotein B, but Is Not Dependent on Apolipoprotein E

Golgi-associated Maturation of Very Low Density Lipoproteins Involves Conformational Changes in Apolipoprotein B, but Is Not Dependent on Apolipoprotein E

Cell Biology of the Endoplasmic Reticulum and the Golgi Apparatus through Proteomics

Sorting by COP I-coated vesicles under interphase and mitotic conditions.

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