Crystal structure of the catalytic portion of human HMG-CoA reductase: insights into regulation of activity and catalysis

Istvan, Eva S.; Palnitkar, Maya; Buchanan, Susan K.; Deisenhofer, Johann

doi:10.1093/emboj/19.5.819

Cited by 280 publications

(244 citation statements)

References 59 publications

Supporting

Mentioning

234

Contrasting

Unclassified

Order By: Relevance

“…This hypothesis is also supported by AMPK enzyme activities found in rat liver lysates that had undergone immunoprecipitation with an antibody directed against the γ 3 -subunit [9]. Changes in PRKAG3-dependent AMPK activity in liver could explain the observed phenotype in minor allele carriers, as AMPK is able to inhibit the key enzyme of cholesterol synthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, by phosphorylation on serine 872 [32][33][34]. In addition, increased LDLcholesterol levels could also be a consequence of altered sterol regulatory element binding transcription factor 1 (SREBP1) function.…”

Section: Discussionmentioning

confidence: 88%

Role of AMP-activated protein kinase gamma 3 genetic variability in glucose and lipid metabolism in non-diabetic whites

et al. 2007

View full text Add to dashboard Cite

Aims/hypothesis AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that acts as an intracellular fuel sensor, directing multiple metabolic pathways in a catabolic direction in times of nutrient shortage. In humans, three different γ-subunits (γ 1 , γ 2 , γ 3 ) have been identified as AMPK regulators. The AMPKγ3 (protein kinase, AMPactivated, gamma 3 non-catalytic subunit, PRKAG3) isoform plays a role in gene regulation in glucose/lipid metabolism and skeletal muscle glycogen content. We investigated whether PRKAG3, in addition to being expressed in skeletal muscle, is also expressed in human liver. We also investigated whether genetic variance in PRKAG3 is associated with glucose and/or lipid metabolism in non-diabetic whites. Materials and methods After sequencing a screening cohort (n=50) in the PRKAG3 locus, we genotyped 1061 participants for frequently found single nucleotide polymorphisms (SNPs). Association analyses between genotypes/ haplotypes and metabolic traits were carried out.Results We detected PRKAG3 expression in human liver and skeletal muscle. Two SNPs (rs692243, rs6436094) with minor allele frequencies of 0.16 and 0.26 respectively and in moderate linkage disequilibrium (D′=0.92; r 2 =0.47) were found.

show abstract

Section: Discussionmentioning

confidence: 88%

Role of AMP-activated protein kinase gamma 3 genetic variability in glucose and lipid metabolism in non-diabetic whites

et al. 2007

View full text Add to dashboard Cite

show abstract

“…In SCAP, this extension is composed of multiple WD-repeat domains that form propeller-like structures that bind SREBPs (12) and also coat proteins that cluster SCAP/SREBP complexes into CopII vesicles that bud from the ER (25). In HMG CoA reductase, the globular cytosolic domain contains all of the catalytic activity of the enzyme (26,27). In both cases the polytopic membrane domain is the site of sterol regulation (8,28), and in both cases the Cterminal extensions can be deleted without abolishing sterol-dependent binding to Insigs (3,29).…”

Section: Discussionmentioning

confidence: 99%

Membrane Topology of Human Insig-1, a Protein Regulator of Lipid Synthesis

Feramisco¹,

Goldstein

Brown

2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Insig-1 is an intrinsic protein of the endoplasmic reticulum (ER) that regulates the proteolytic processing of membrane-bound sterol regulatory element-binding proteins (SREBPs), transcription factors that activate the synthesis of cholesterol and fatty acids in mammalian cells. When cellular levels of sterols rise, Insig-1 binds to the membranous sterol-sensing domain of SREBP cleavage-activating protein (SCAP), retaining the SCAP/SREBP complex in the ER and preventing it from moving to the Golgi for proteolytic processing. Under conditions of sterol excess, Insig-1 also binds to the ER enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, facilitating its ubiquitination and proteasomal degradation. Here, we use protease protection, glycosylation site mapping, and cysteine derivitization to define the topology of the 277-amino acid human Insig-1. The data indicate that short segments at the N and C termini of Insig-1 face the cytosol. Most of the protein is buried within the membrane, forming six transmembrane segments separated by five short luminal and cytosolic loops that range from ϳ5 to 16 amino acids. The membranous nature of Insig-1 is consistent with its sterol-dependent binding to hydrophobic sterolsensing domains in SCAP and HMG CoA reductase.

show abstract

“…Mammalian HMGR is an integral high mannose glycoprotein of the ER (Brown and Simoni, 1984;Liscum et al, 1985). Structurally, it is divided into two major domains: a C-terminal cytosol-facing domain that tetramerizes to form the active sites (Liscum et al, 1985;Istvan et al, 2000) and an N-terminal hydrophobic region that spans the ER membrane 8 times and bears a single N-glycan (Liscum et al, 1983). This membrane region is dispensable for the enzymatic activity (Gil et al, 1985), but it is necessary for the metabolically controlled stability of the enzyme (Gil et al, 1985) and sufficient to confer sterol-accelerated degradation onto heterologous proteins (Skalnik et al, 1988;Cheng et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Dislocation of HMG-CoA Reductase and Insig-1, Two Polytopic Endoplasmic Reticulum Proteins, En Route to Proteasomal Degradation

Leichner

Avner

Harats

et al. 2009

MBoC

View full text Add to dashboard Cite

The endoplasmic reticulum (ER) glycoprotein HMG-CoA reductase (HMGR) catalyzes the rate-limiting step in sterols biosynthesis. Mammalian HMGR is ubiquitinated and degraded by the proteasome when sterols accumulate in cells, representing the best example for metabolically controlled ER-associated degradation (ERAD). This regulated degradation involves the short-lived ER protein Insig-1. Here, we investigated the dislocation of these ERAD substrates to the cytosol en route to proteasomal degradation. We show that the tagged HMGR membrane region, HMG 350 INTRODUCTIONA key mechanism for maintaining cholesterol homeostasis in mammalian cells involves modulating the stability of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR). This enzyme catalyzes the rate-limiting step in the mevalonate (MVA) pathway in which essential sterols and nonsterol isoprenoids are synthesized (Goldstein and Brown, 1990). In cells deprived of sterols and/or MVA-derived isoprenoids, HMGR is a fairly stable protein that turns over with a half-life of 10 -14 h. Conversely, in cells replenished with MVA pathway products, HMGR degradation is accelerated severalfold and its half-life drops to 1-4 h (Faust et al., 1982;Edwards et al., 1983;Sinensky and Logel, 1983), reflecting one of the highly regulated processes that prevent accumulation of these metabolites to toxic levels.Similar to other proteins of the MVA pathway (Horton et al., 2002), HMGR is controlled also at the transcriptional level by the sterol regulatory element-binding protein (SREBP)-2, which binds to the promoter of the HMGR gene and activates transcription when demands for MVA-derived products increase (Osborne et al., 1985;Vallett et al., 1996). Like its closely related SREBP-1a and SREBP-1c factors, SREBP-2 is synthesized as a large endoplasmic reticulum (ER)-bound precursor whose transcription activation domain must be released from the membrane to function in the nucleus. On increased demand for MVA-derived metabolites, the SREBP precursor is transported by COP-II vesicles to the Golgi, where it is sequentially cleaved at two sites by resident site-1 and site-2 proteases. The liberated transcriptionally active domain enters the nucleus and stimulates the transcription of target genes, including HMGR (Sakai et al., 1996;Nohturfft et al., 1998aNohturfft et al., , 2000. When sterols are abundant and demand for MVA-derived products declines, the transport of the SREBP precursor out from the ER is prevented and transcription ceases (Nohturfft et al., 1999(Nohturfft et al., , 2000. This metabolically regulated traffic of the SREBP precursors critically depends on SREBP cleavage-activating protein (SCAP), a membrane protein with eight transmembranes spans (TMs), which tightly associates with the SREBP precursors and enables the packaging of both proteins in the COP-II vesicles and their transport from the ER to the Golgi Sakai et al., 1997;Nohturfft et al., 1998b Feramisco et al., 2004). This sterol-stimulated binding to Insig(s) masks the transport signal in SCAP and abrogates i...

show abstract

Crystal structure of the catalytic portion of human HMG-CoA reductase: insights into regulation of activity and catalysis

Cited by 280 publications

References 59 publications

Role of AMP-activated protein kinase gamma 3 genetic variability in glucose and lipid metabolism in non-diabetic whites

Role of AMP-activated protein kinase gamma 3 genetic variability in glucose and lipid metabolism in non-diabetic whites

Membrane Topology of Human Insig-1, a Protein Regulator of Lipid Synthesis

Dislocation of HMG-CoA Reductase and Insig-1, Two Polytopic Endoplasmic Reticulum Proteins, En Route to Proteasomal Degradation

Contact Info

Product

Resources

About