scholarly journals Immunological evidence for eight spans in the membrane domain of 3-hydroxy-3-methylglutaryl coenzyme A reductase: implications for enzyme degradation in the endoplasmic reticulum

1992 ◽  
Vol 117 (5) ◽  
pp. 959-973 ◽  
Author(s):  
J Roitelman ◽  
EH Olender ◽  
S Bar-Nun ◽  
WA Dunn ◽  
RD Simoni
Keyword(s):  
Endoplasmic Reticulum ◽  
Coenzyme A ◽  
Cultured Cells ◽  
Critical Role ◽  
Transmembrane Helix ◽  
Chimeric Protein ◽  
Membrane Domain ◽  
Hmg Coa Reductase ◽  
Coa Reductase ◽  
Peptide G

We have raised two monospecific antibodies against synthetic peptides derived from the membrane domain of the ER glycoprotein 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate limiting enzyme in the cholesterol biosynthetic pathway. This domain, which was proposed to span the ER membrane seven times (Liscum, L., J. Finer-Moore, R. M. Stroud, K. L. Luskey, M. S. Brown, and J. L. Goldstein. 1985. J. Biol. Chem. 260:522-538), plays a critical role in the regulated degradation of the enzyme in the ER in response to sterols. The antibodies stain the ER of cells and immunoprecipitate HMG-CoA reductase and HMGal, a chimeric protein composed of the membrane domain of the reductase fused to Escherichia coli beta-galactosidase, the degradation of which is also accelerated by sterols. We show that the sequence Arg224 through Leu242 of HMG-CoA reductase (peptide G) faces the cytoplasm both in cultured cells and in rat liver, whereas the sequence Thr284 through Glu302 (peptide H) faces the lumen of the ER. This indicates that a sequence between peptide G and peptide H spans the membrane of the ER. Moreover, by epitope tagging with peptide H, we show that the loop segment connecting membrane spans 3 and 4 is sequestered in the lumen of the ER. These results demonstrate that the membrane domain of HMG-CoA reductase spans the ER eight times and are inconsistent with the seven membrane spans topological model. The approximate boundaries of the proposed additional transmembrane segment are between Lys248 and Asp276. Replacement of this 7th span in HMGal with the first transmembrane helix of bacteriorhodopsin abolishes the sterol-enhanced degradation of the protein, indicating its role in the regulated turnover of HMG-CoA reductase within the endoplasmic reticulum.

The regulated degradation of a 3-hydroxy-3-methylglutaryl-coenzyme A reductase reporter construct occurs in the endoplasmic reticulum

1994 ◽  
Vol 107 (9) ◽  
pp. 2635-2642
Author(s):  
L.W. Lecureux ◽  
B.W. Wattenberg
Keyword(s):  
Endoplasmic Reticulum ◽  
Coenzyme A ◽  
Cholesterol Biosynthesis ◽  
Mevalonic Acid ◽  
Dna Encoding ◽  
Hmg Coa Reductase ◽  
Steady State Levels ◽  
Coa Reductase ◽  
Membrane Anchoring ◽  
Beta Galactosidase

The rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase, is regulated at a number of levels. One important mechanism is regulation of the half-life of the protein by a controlled proteolytic system. This comes about in response to downstream products of the sterol biosynthetic pathway. Little is known about this system, including where in the cell this regulated degradation occurs. HMG CoA reductase resides in the endoplasmic reticulum. To localize the site of regulated degradation of HMG CoA reductase, we used a construct that fuses the N-terminal membrane-anchoring domain of HMG CoA reductase in-frame with beta-galactosidase as a reporter domain (HM-Gal). HM-Gal has previously been shown to reproduce faithfully the degradative properties of native HMG CoA reductase (Chun et al. (1990) J. Biol. Chem. 265, 22004–22010). CHO cells transfected with DNA encoding HM-Gal were exposed to mevalonic acid, which enhances the rate of HMG CoA reductase degradation several fold, and leads to the reduction of the steady state levels of HM-Gal by 80–90%. To accumulate HMG CoA reductase at the site of degradation, cells were simultaneously treated with N-acetyl-leucyl-leucyl-norleucinal (ALLN), which inhibits the protease responsible for reductase degradation. HM-Gal was localized morphologically by immunofluorescence and biochemically by measuring beta-galactosidase activity in Percoll gradients of cellular homogenates. Using either technique HM-Gal localization was indistinguishable from that of ER markers in both control cells and in cells treated to accumulate HMG CoA reductase at the site of degradation.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and biochemical evaluation of eucaryotic membrane protein topology: multiple transmembrane domains of Saccharomyces cerevisiae 3-hydroxy-3-methylglutaryl coenzyme A reductase

1990 ◽  
Vol 10 (2) ◽  
pp. 672-680
Author(s):  
C Sengstag ◽  
C Stirling ◽  
R Schekman ◽  
J Rine
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Coenzyme A ◽  
Transmembrane Domains ◽  
Protein Domain ◽  
Yeast Cells ◽  
Endoplasmic Reticulum Membrane ◽  
Hmg Coa Reductase ◽  
Coa Reductase ◽  
Histidinol Dehydrogenase

Both 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase isozymes of the yeast Saccharomyces cerevisiae are predicted to contain seven membrane-spanning domains. Previous work had established the utility of the histidinol dehydrogenase protein domain, encoded by HIS4C, as a topologically sensitive monitor that can be used to distinguish between the lumen of the endoplasmic reticulum and the cytoplasm. This study directly tested the structural predictions for HMG-CoA reductase by fusing the HIS4C domain to specific sites in the HMG-CoA reductase isozymes. Yeast cells containing the HMG-CoA reductase-histidinol dehydrogenase fusion proteins grew on histidinol-containing medium if the HIS4C domain was present on the cytoplasmic side of the endoplasmic reticulum membrane but not if the HIS4C domain was targeted to the endoplasmic reticulum lumen. Systematic exchanges of transmembrane domains between the isozymes confirmed that both isozymes had equivalent membrane topologies. In general, deletion of an even number of putative transmembrane domains did not interfere with the topology of the protein, but deletion or duplication of an odd number of transmembrane domains inverted the orientation of the protein. The data confirmed the earlier proposed topology for yeast HMG-CoA reductase, demonstrated that the yeast enzymes are core glycosylated, and provided in vivo evidence that the properties of transmembrane domains were, in part, dependent upon their context within the protein.

scholarly journals The Role of the 3-Hydroxy 3-Methylglutaryl Coenzyme A Reductase Cytosolic Domain in Karmellae Biogenesis

1999 ◽  
Vol 10 (10) ◽  
pp. 3409-3423 ◽  
Author(s):  
Deborah A. Profant ◽  
Christopher J. Roberts ◽  
Ann J. Koning ◽  
Robin L. Wright
Keyword(s):  
Coenzyme A ◽  
Tertiary Structure ◽  
Catalytic Domain ◽  
Carboxyl Terminus ◽  
Membrane Domain ◽  
Hmg Coa Reductase ◽  
Cytosolic Domain ◽  
Coa Reductase ◽  
Er Membrane

In all cells examined, specific endoplasmic reticulum (ER) membrane arrays are induced in response to increased levels of the ER membrane protein 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase. In yeast, expression of Hmg1p, one of two yeast HMG-CoA reductase isozymes, induces assembly of nuclear-associated ER stacks called karmellae. Understanding the features of HMG-CoA reductase that signal karmellae biogenesis would provide useful insights into the regulation of membrane biogenesis. The HMG-CoA reductase protein consists of two domains, a multitopic membrane domain and a cytosolic catalytic domain. Previous studies had indicated that the HMG-CoA reductase membrane domain was exclusively responsible for generation of ER membrane proliferations. Surprisingly, we discovered that this conclusion was incorrect: sequences at the carboxyl terminus of HMG-CoA reductase can profoundly affect karmellae biogenesis. Specifically, truncations of Hmg1p that removed or shortened the carboxyl terminus were unable to induce karmellae assembly. This result indicated that the membrane domain of Hmg1p was not sufficient to signal for karmellae assembly. Using β-galactosidase fusions, we demonstrated that the carboxyl terminus was unlikely to simply serve as an oligomerization domain. Our working hypothesis is that a truncated or misfolded cytosolic domain prevents proper signaling for karmellae by interfering with the required tertiary structure of the membrane domain.

scholarly journals Genetic and biochemical evaluation of eucaryotic membrane protein topology: multiple transmembrane domains of Saccharomyces cerevisiae 3-hydroxy-3-methylglutaryl coenzyme A reductase.

1990 ◽  
Vol 10 (2) ◽  
pp. 672-680 ◽  
Author(s):  
C Sengstag ◽  
C Stirling ◽  
R Schekman ◽  
J Rine
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Coenzyme A ◽  
Transmembrane Domains ◽  
Protein Domain ◽  
Yeast Cells ◽  
Endoplasmic Reticulum Membrane ◽  
Hmg Coa Reductase ◽  
Coa Reductase ◽  
Histidinol Dehydrogenase

Both 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase isozymes of the yeast Saccharomyces cerevisiae are predicted to contain seven membrane-spanning domains. Previous work had established the utility of the histidinol dehydrogenase protein domain, encoded by HIS4C, as a topologically sensitive monitor that can be used to distinguish between the lumen of the endoplasmic reticulum and the cytoplasm. This study directly tested the structural predictions for HMG-CoA reductase by fusing the HIS4C domain to specific sites in the HMG-CoA reductase isozymes. Yeast cells containing the HMG-CoA reductase-histidinol dehydrogenase fusion proteins grew on histidinol-containing medium if the HIS4C domain was present on the cytoplasmic side of the endoplasmic reticulum membrane but not if the HIS4C domain was targeted to the endoplasmic reticulum lumen. Systematic exchanges of transmembrane domains between the isozymes confirmed that both isozymes had equivalent membrane topologies. In general, deletion of an even number of putative transmembrane domains did not interfere with the topology of the protein, but deletion or duplication of an odd number of transmembrane domains inverted the orientation of the protein. The data confirmed the earlier proposed topology for yeast HMG-CoA reductase, demonstrated that the yeast enzymes are core glycosylated, and provided in vivo evidence that the properties of transmembrane domains were, in part, dependent upon their context within the protein.

scholarly journals Partial deletion of membrane-bound domain of 3-hydroxy-3-methylglutaryl coenzyme A reductase eliminates sterol-enhanced degradation and prevents formation of crystalloid endoplasmic reticulum.

1987 ◽  
Vol 104 (6) ◽  
pp. 1693-1704 ◽  
Author(s):  
H Jingami ◽  
M S Brown ◽  
J L Goldstein ◽  
R G Anderson ◽  
K L Luskey
Keyword(s):  
Endoplasmic Reticulum ◽  
Half Life ◽  
Coenzyme A ◽  
Catalytic Domain ◽  
Carbohydrate Chain ◽  
Hmg Coa Reductase ◽  
Membrane Bound ◽  
Membrane Spanning ◽  
Coa Reductase ◽  
Er Membrane

3-Hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase is anchored to the endoplasmic reticulum (ER) membrane by a hydrophobic NH2-terminal domain that contains seven apparent membrane-spanning regions and a single N-linked carbohydrate chain. The catalytic domain, which includes the COOH-terminal two-thirds of the protein, extends into the cytoplasm. The enzyme is normally degraded with a rapid half-life (2 h), but when cells are depleted of cholesterol, its half-life is prolonged to 11 h. Addition of sterols accelerates degradation by fivefold. To explore the requirements for regulated degradation, we prepared expressible reductase cDNAs from which we either deleted two contiguous membrane-spanning regions (numbers 4 and 5) or abolished the single site for N-linked glycosylation. When expressed in hamster cells after transfection, both enzymes retained catalytic activity. The deletion-bearing enzyme continued to be degraded with a rapid half-life in the presence of sterols, but it no longer was stabilized when sterols were depleted. The glycosylation-minus enzyme was degraded at a normal rate and was stabilized normally by sterol deprivation. When cells were induced to overexpress the deletion-bearing enzyme, they did not incorporate it into neatly arranged crystalloid ER tubules, as occurred with the normal and carbohydrate-minus enzymes. Rather, the deletion-bearing enzyme was incorporated into hypertrophied but disordered sheets of ER membrane. We conclude that the carbohydrate component of HMG CoA reductase is not required for proper subcellular localization or regulated degradation. In contrast, the native structure of the transmembrane component is required to form a normal crystalloid ER and to allow the enzyme to undergo regulated degradation by sterols.

scholarly journals Loose Morphology and High Dynamism of OSER Structures Induced by the Membrane Domain of HMG-CoA Reductase

2021 ◽  
Vol 22 (17) ◽  
pp. 9132
Author(s):  
Ricardo Enrique Grados-Torrez ◽  
Carmen López-Iglesias ◽  
Joan Carles Ferrer ◽  
Narciso Campos
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Eukaryotic Cell ◽  
Membrane Association ◽  
Membrane Domain ◽  
Active Components ◽  
Hmg Coa Reductase ◽  
Intracellular Movement ◽  
Coa Reductase ◽  
Confocal And Electron Microscopy

The membrane domain of eukaryotic HMG-CoA reductase (HMGR) has the conserved capacity to induce endoplasmic reticulum (ER) proliferation and membrane association into Organized Smooth Endoplasmic Reticulum (OSER) structures. These formations develop in response to overexpression of particular proteins, but also occur naturally in cells of the three eukaryotic kingdoms. Here, we characterize OSER structures induced by the membrane domain of Arabidopsis HMGR (1S domain). Immunochemical confocal and electron microscopy studies demonstrate that the 1S:GFP chimera co-localizes with high levels of endogenous HMGR in several ER compartments, such as the ER network, the nuclear envelope, the outer and internal membranes of HMGR vesicles and the OSER structures, which we name ER-HMGR domains. After high-pressure freezing, ER-HMGR domains show typical crystalloid, whorled and lamellar ultrastructural patterns, but with wide heterogeneous luminal spaces, indicating that the native OSER is looser and more flexible than previously reported. The formation of ER-HMGR domains is reversible. OSER structures grow by incorporation of ER membranes on their periphery and progressive compaction to the inside. The ER-HMGR domains are highly dynamic in their formation versus their disassembly, their variable spherical-ovoid shape, their fluctuating borders and their rapid intracellular movement, indicating that they are not mere ER membrane aggregates, but active components of the eukaryotic cell.

scholarly journals Dietary modification of the activation state of intestinal 3-hydroxy-3-methylglutaryl coenzyme a (HMG-CoA) reductase.

1984 ◽  
Vol 48 (11) ◽  
pp. 2745-2751
Author(s):  
Hirosuke OKU ◽  
Akira MORITA ◽  
Takashi IDE ◽  
Michihiro SUGANO
Keyword(s):  
Coenzyme A ◽  
Dietary Modification ◽  
Hmg Coa Reductase ◽  
Coa Reductase
Sign in / Sign up

Export Citation Format

Share Document