Functional Interaction between Cytochrome P450 and UDP-Glucuronosyltransferase on the Endoplasmic Reticulum Membrane: One of Post-translational Factors Which Possibly Contributes to Their Inter-Individual Differences

Contribution of translocon peptide channels to the permeation of low molecular mass anions was investigated in rat liver microsomes. Puromycin, which purges translocon pores of nascent polypeptides, creating additional empty pores, raised the microsomal uptake of radiolabeled UDP-glucuronic acid, while it did not increase the uptake of glucose-6-phosphate or glutathione. The role of translocon pores in the transport of small anions was also investigated by measuring the effect of puromycin on the activity of microsomal enzymes with intraluminal active sites. The mannose-6-phosphatase activity of glucose-6-phosphatase and the activity of UDP-glucuronosyltransferase were elevated upon addition of puromycin, but glucose-6-phosphatase and β-glucuronidase activities were not changed. The increase in enzyme activities was due to a better access of the substrates to the luminal compartment rather than to activation of the enzymes. Antibody against Sec61 translocon component decreased the activity of UDP-glucuronosyltransferase and antagonized the effect of puromycin. Similarly, the addition of the puromycin antagonist anisomycin or treatments of microsomes, resulting in the release of attached ribosomes, prevented the puromycin-dependent increase in the activity. Mannose-6-phosphatase and UDP-glucuronosyltransferase activities of smooth microsomal vesicles showed higher basal latencies that were not affected by puromycin. In conclusion, translationally inactive, ribosome-bound translocons allow small anions to cross the endoplasmic reticulum membrane. This pathway can contribute to the nonspecific substrate supply of enzymes with intraluminal active centers.

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Effects of Compatible Solutes on Mammalian Cytochrome P450 Stability

Zeitschrift für Naturforschung C ◽

10.1515/znc-1997-1-223 ◽

1997 ◽

Vol 52 (1-2) ◽

pp. 132-136 ◽

Cited By ~ 7

Author(s):

W. Nikolaus Kühn-Velten

Keyword(s):

Endoplasmic Reticulum ◽

Cytochrome P450 ◽

Compatible Solutes ◽

Compatible Solute ◽

Heat Denaturation ◽

Endoplasmic Reticulum Membrane ◽

Protective Effects ◽

Spectral Transition ◽

Membrane Bound

AbstractThe sensitivity of pig cytochrome P450cl7 (CYP17), an endoplasmic reticulum membrane-bound enzyme, towards heat denaturation (48 °C) was measured by the P450-to-P420 spectral transition indicating conformational labilization of the protein. Both sucrose and glucose have comparable and increasingly protective effects at concentrations ranging from 100 to 800 mм, while ectoine, a novel zwitterionic compatible solute which regulates bacterial osmoadaptation and stabilizes cytoplasmic enzymes, has a strong labilizing effect on CYP17 and favours its proteolytic inactivation possibly by electrostatic derangements. Sucrose or glucose, but not ectoine, can therefore eventually be proposed as compatible stabilizers of cytochrome P450 structures.

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Molecular Dysfunctions of Mitochondria-Associated Endoplasmic Reticulum Contacts in Atherosclerosis

Oxidative Medicine and Cellular Longevity ◽

10.1155/2021/2424509 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Xiaojiao Wang ◽

Dan Luo ◽

Sisi Wu

Keyword(s):

Endoplasmic Reticulum ◽

Percolation Theory ◽

Arterial Wall ◽

Immune Cell ◽

Endoplasmic Reticulum Membrane ◽

High Morbidity ◽

Functional Interaction ◽

Mutation Theory ◽

The World

Atherosclerosis is a chronic lipid-driven inflammatory disease that results in the formation of lipid-rich and immune cell-rich plaques in the arterial wall, which has high morbidity and mortality in the world. The mechanism of atherosclerosis is still unclear now. Potential hypotheses involved in atherosclerosis are chronic inflammation theory, lipid percolation theory, mononuclear-macrophage theory, endothelial cell (EC) injury theory, and smooth muscle cell (SMC) mutation theory. Changes of phospholipids, glucose, critical proteins, etc. on mitochondria-associated endoplasmic reticulum membrane (MAM) can cause the progress of atherosclerosis. This review describes the structural and functional interaction between mitochondria and endoplasmic reticulum (ER) and explains the role of critical molecules in the structure of MAM during atherosclerosis.

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Mobility of cytochrome P450 in the endoplasmic reticulum membrane

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.95.25.14793 ◽

1998 ◽

Vol 95 (25) ◽

pp. 14793-14798 ◽

Cited By ~ 51

Author(s):

E. Szczesna-Skorupa ◽

C.-D. Chen ◽

S. Rogers ◽

B. Kemper

Keyword(s):

Endoplasmic Reticulum ◽

Cytochrome P450 ◽

Endoplasmic Reticulum Membrane

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Evolutionary conserved nitric oxide synthesis proteins responding to bacterial MAMPs are located to the endoplasmic reticulum and are also involved in secondary metabolite synthesis and sterol production

10.1101/2020.07.12.191361 ◽

2020 ◽

Author(s):

Wenhui Zheng ◽

Hongchen Li ◽

Simon Ipcho ◽

Wenqin Fang ◽

Rosanna Hennessey ◽

...

Keyword(s):

Nitric Oxide ◽

Endoplasmic Reticulum ◽

Cytochrome P450 ◽

Alpha Helix ◽

Sterol Synthesis ◽

Endoplasmic Reticulum Membrane ◽

No Production ◽

Ergosterol Synthesis ◽

Metabolite Synthesis ◽

Eukaryotic Organisms

AbstractNitric oxide is (NO) known to be produced by most Eukaryotic organisms although the NO production mechanism is only known for animals (Cánovas et al., 2016). Mammals have a set of different nitric oxide synthases (NOSs) with basically similar mechanism for producing NO under different circumstances (Velayutham and Zweier, 2013; Yu et al., 2014). NO-production is characteristically induced as part of innate immunity reactions to bacterial Microbial Associated Molecular Patterns (MAMPs). We knew from our previous work that the plant pathogen Fusarium graminearum quickly upregulates genes characteristic for an innate immune response so we set out to test if it also produces NO as part of this response and find the responsible genes if it does.We found that F. graminearum produces NO in response to bacterial MAMPs and that the NO production system must be similar in fungi as in mammals where NO is activated by a homo-dimerization of nitric oxide synthetase proteins (NOSs) containing an N-terminal cytochrome P450 domain (CYP) and a C-terminal NADPH dependent cytochrome P450 reductase (NCP) domain. The electrons are transferred from the C-terminal NCP domains to the CYP domain in the paired protein to produce NO. We could not find a candidate NOS in the fungus. Thus, we tested the hypothesis that an NCP-protein similar to the NCP part of a NOS is brought together with a CYP-protein to produce NO in another way than the dimerization of a classic NOS. We found that in F. graminearum NO is produced by an FgNCP and an FgCYP located to the endoplasmic reticulum membrane where both proteins are predicted to be N-terminally attached by a transmembrane or embedded hydrophobic alpha helix. Deletion of any of these proteins lowered pathogenicity to wheat and radically reduced NO-production. Knockout of the FgNCP also completely blocked deoxynivalenol synthesis needed for pathogenicity indicating that the FgNCP also delivers electrons to another CYP (TRI4) located at the ER. The FgCYP we found to be involved in NO-productions is the same or similar to proteins involved in Eukaryote sterol synthesis (CYP51) reducing lanosterol on the way to the final main sterols different for different Eukaryotes. Lanosterol enriched membranes are known to be inhibited in endocytosis and we found that the deletion of the FgCYP producing NO also completely stopped endocytosis. We further tested consequences of these indications of more than one function and suggest the CYP-protein is most likely an FgCYPNO,ERG involved in both NO and ergosterol synthesis and the NCP is involved in NO, trichothecene and ergosterol synthesis, an FgNCPNO,TRI,ERG. The two proteins shown here to be responsible for NO production in F. graminearum are both highly conserved in Eukaryotes from amoeba to human and homologues are likely candidates for the production of NO in many other eukaryotes including mammals. The multiple functions of these proteins can be part of the explanation for the links between chronic inflammation, sterols and blood pressure in human.

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Uridine diphosphoxylose enhances hepatic microsomal UDP-glucuronosyltransferase activity by stimulating transport of UDP-glucuronic acid across the endoplasmic reticulum membrane

Biochemical Journal ◽

10.1042/bj3150189 ◽

1996 ◽

Vol 315 (1) ◽

pp. 189-193 ◽

Cited By ~ 6

Author(s):

Xavier BOSSUYT ◽

Norbert BLANCKAERT

Keyword(s):

Endoplasmic Reticulum ◽

Glucuronic Acid ◽

Endoplasmic Reticulum Membrane ◽

Acid Uptake ◽

Physiological Importance ◽

Cytosolic Side ◽

Udp Glucuronosyltransferase ◽

Exogenous Compounds ◽

Stimulation Of ◽

Er Membrane

The UDP-glucuronosyltransferase (UGT) system fulfils a pivotal role in the biotransformation of potentially toxic endogenous and exogenous compounds. Here we report that the activity of UGT in rat liver is stimulated by UDP-xylose. This stimulation was found in native microsomal vesicles as well as in the intact endoplasmic reticulum (ER) membrane, as studied in permeabilized hepatocytes, indicating the potential physiological importance of UDP-xylose in the regulation of UGT. We present evidence that UDP-xylose enhances UGT activity by stimulation of (i) the uptake of UDP-glucuronic acid across the ER membrane and (ii) the elimination of the UDP and/or UMP reaction product out of the ER lumen. UDP-xylose produced a marked trans-stimulation of microsomal UDP-glucuronic acid uptake when it was present within the lumen of the ER. When UDP-xylose was presented at the cytosolic side of the ER, it acted as a weak inhibitor of UDP-glucuronic acid uptake. Likewise, cytosolic UDP-glucuronic acid strongly trans-stimulated efflux of intravesicular UDP-xylose, whereas cytosolic UDP-xylose was inefficient in trans-stimulating efflux of UDP-glucuronic acid. Microsomal UDP-xylose influx was markedly stimulated by UMP and UDP. Such stimulation was only apparent when microsomes had been preincubated and thereby preloaded with UMP or UDP, indicating that UMP and UDP exerted their effect on UDP-xylose uptake by trans-stimulation from the luminal side of the ER membrane.

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