scholarly journals Identification of the sequences in HMG-CoA reductase required for karmellae assembly.

1995 ◽  
Vol 6 (11) ◽  
pp. 1535-1547 ◽  
Author(s):  
M L Parrish ◽  
C Sengstag ◽  
J D Rine ◽  
R L Wright
Keyword(s):  
Cellular Responses ◽  
Cell Periphery ◽  
Membrane Domain ◽  
Hmg Coa Reductase ◽  
Simple Possibility ◽  
Coa Reductase ◽  
Necessary And Sufficient ◽  
Specific Membrane ◽  
Molecular Nature ◽  
Er Membrane

In all eukaryotic cells that have been examined, specific membrane arrays are induced in response to increased levels of the ER membrane protein, HMG-CoA reductase. Analysis of these inducible membranes has the potential to reveal basic insights into general membrane assembly. Yeast express two HMG-CoA reductase isozymes, and each isozyme induces a morphologically distinct proliferation of the endoplasmic reticulum. The isozyme encoded by HMG1 induces karmellae, which are long stacks of membranes that partially enclose the nucleus. In contrast, the isozyme encoded by HMG2 induces short stacks of membrane that may be associated with the nucleus, but are frequently present at the cell periphery. To understand the molecular nature of the different cellular responses to Hmg1p and Hmg2p, we mapped the region of Hmg1p that is needed for karmellae assembly. For this analysis, a series of exchange alleles was examined in which a portion of the Hmg2p membrane domain was replaced with the corresponding Hmg1p sequences. Results of this analysis indicated that the ER lumenal loop between predicted transmembrane domains 6 and 7 was both necessary and sufficient for karmellae assembly, when present in the context of an HMG-CoA reductase membrane domain. Immunoblotting experiments ruled out the simple possibility that differences in the amounts of the various chimeric HMG-CoA reductase proteins was responsible for the altered cellular responses. Our results are consistent with the hypothesis that each yeast isozyme induces or organizes a qualitatively different organization of ER membrane.

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 Different subcellular localization of Saccharomyces cerevisiae HMG-CoA reductase isozymes at elevated levels corresponds to distinct endoplasmic reticulum membrane proliferations.

1996 ◽  
Vol 7 (5) ◽  
pp. 769-789 ◽  
Author(s):  
A J Koning ◽  
C J Roberts ◽  
R L Wright
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Subcellular Localization ◽  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Endoplasmic Reticulum Membrane ◽  
Hmg Coa Reductase ◽  
Endogenous Expression ◽  
Coa Reductase ◽  
Er Membrane

In all eucaryotic cell types analyzed, proliferations of the endoplasmic reticulum (ER) can be induced by increasing the levels of certain integral ER proteins. One of the best characterized of these proteins is HMG-CoA reductase, which catalyzes the rate-limiting step in sterol biosynthesis. We have investigated the subcellular distributions of the two HMG-CoA reductase isozymes in Saccharomyces cerevisiae and the types of ER proliferations that arise in response to elevated levels of each isozyme. At endogenous expression levels, Hmg1p and Hmg2p were both primarily localized in the nuclear envelope. However, at increased levels, the isozymes displayed distinct subcellular localization patterns in which each isozyme was predominantly localized in a different region of the ER. Specifically, increased levels of Hmg1p were concentrated in the nuclear envelope, whereas increased levels of Hmg2p were concentrated in the peripheral ER. In addition, an Hmg2p chimeric protein containing a 77-amino acid lumenal segment from Hmg1p was localized in a pattern that resembled that of Hmg1p when expressed at increased levels. Reflecting their different subcellular distributions, elevated levels of Hmg1p and Hmg2p induced sets of ER membrane proliferations with distinct morphologies. The ER membrane protein, Sec61p, was localized in the membranes induced by both Hmg1p and Hmg2p green fluorescent protein (GFP) fusions. In contrast, the lumenal ER protein, Kar2p, was present in Hmg1p:GFP membranes, but only rarely in Hmg2p:GFP membranes. These results indicated that the membranes synthesized in response to Hmg1p and Hmg2p were derived from the ER, but that the membranes were not identical in protein composition. We determined that the different types of ER proliferations were not simply due to quantitative differences in protein amounts or to the different half-lives of the two isozymes. It is possible that the specific distributions of the two yeast HMG-CoA reductase isozymes and their corresponding membrane proliferations may reveal regions of the ER that are specialized for certain branches of the sterol biosynthetic pathway.

Bisphosphonate esters interact with HMG-CoA reductase membrane domain to induce its degradation

2020 ◽  
Vol 28 (14) ◽  
pp. 115576 ◽  
Author(s):  
Yosuke Toyota ◽  
Hiromasa Yoshioka ◽  
Ikuya Sagimori ◽  
Yuichi Hashimoto ◽  
Kenji Ohgane
Keyword(s):  
Membrane Domain ◽  
Hmg Coa Reductase ◽  
Coa Reductase

scholarly journals Regulation of Hmg-Coa Reductase Degradation Requires the P-Type Atpase Cod1p/Spf1p

2000 ◽  
Vol 148 (5) ◽  
pp. 915-924 ◽  
Author(s):  
Stephen R. Cronin ◽  
Afif Khoury ◽  
Dana K. Ferry ◽  
Randolph Y. Hampton
Keyword(s):  
Membrane Protein ◽  
Mevalonate Pathway ◽  
Hmg Coa Reductase ◽  
Key Enzyme ◽  
Coa Reductase ◽  
P Type ◽  
Calcium Transporter ◽  
Er Membrane

The integral ER membrane protein HMG-CoA reductase (HMGR) is a key enzyme of the mevalonate pathway from which sterols and other essential molecules are produced. HMGR degradation occurs in the ER and is regulated by mevalonate-derived signals. Little is known about the mechanisms responsible for regulating HMGR degradation. The yeast Hmg2p isozyme of HMGR undergoes regulated degradation in a manner very similar to mammalian HMGR, allowing us to isolate mutants deficient in regulating Hmg2p stability. We call these mutants cod mutants for the control of HMG-CoA reductase degradation. With this screen, we have identified the first gene of this class, COD1, which encodes a P-type ATPase and is identical to SPF1. Our data suggested that Cod1p is a calcium transporter required for regulating Hmg2p degradation. This role for Cod1p is distinctly different from that of the well-characterized Ca2+ P-type ATPase Pmr1p which is neither required for Hmg2p degradation nor its control. The identification of Cod1p is especially intriguing in light of the role Ca2+ plays in the regulated degradation of mammalian HMGR.

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.

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.

Reduction of HMG-CoA-reductase leads to improved cardiac function in doxorubicin-induced cardiomyopathy in mice

2008 ◽  
Vol 7 ◽  
pp. 202-203
Author(s):  
A RIAD ◽  
S BIEN ◽  
F ESCHER ◽  
D WESTERMANN ◽  
U LANDMESSER ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Hmg Coa Reductase ◽  
Coa Reductase
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