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Low reduction potential of Ero1alpha regulatory disulphides ensures tight control of substrate oxidation.

ABSTRACT: Formation of disulphide bonds within the mammalian endoplasmic reticulum (ER) requires the combined activities of Ero1alpha and protein disulphide isomerase (PDI). As Ero1alpha produces hydrogen peroxide during oxidation, regulation of its activity is critical in preventing ER-generated oxidative stress. Here, we have expressed and purified recombinant human Ero1alpha and shown that it has activity towards thioredoxin and PDI. The activity towards PDI required the inclusion of glutathione to ensure sustained oxidation. By carrying out site-directed mutagenesis of cysteine residues, we show that Ero1alpha is regulated by non-catalytic disulphides. The midpoint reduction potential (E degrees') of the regulatory disulphides was calculated to be approximately -275 mV making them stable in the redox conditions prevalent in the ER. The stable regulatory disulphides were only partially reduced by PDI (E degrees' approximately -180 mV), suggesting either that this is a mechanism for preventing excessive Ero1alpha activity and oxidation of PDI or that additional factors are required for Ero1alpha activation within the mammalian ER.

SUBMITTER: Baker KM

PROVIDER: S-EPMC2579255 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Low reduction potential of Ero1alpha regulatory disulphides ensures tight control of substrate oxidation.

Baker Karl M KM Chakravarthi Seema S Langton Kevin P KP Sheppard Alyson M AM Lu Hui H Bulleid Neil J NJ

The EMBO journal 20081030 22

Formation of disulphide bonds within the mammalian endoplasmic reticulum (ER) requires the combined activities of Ero1alpha and protein disulphide isomerase (PDI). As Ero1alpha produces hydrogen peroxide during oxidation, regulation of its activity is critical in preventing ER-generated oxidative stress. Here, we have expressed and purified recombinant human Ero1alpha and shown that it has activity towards thioredoxin and PDI. The activity towards PDI required the inclusion of glutathione to ens ...[more]

PMID: 18971943

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Project description:Male Infertility Oxidative System (MiOXSYS) has been proposed as a rapid and promising technology for the evaluation of sperm oxidative stress. In this case-control study, 134 men with normal sperm parameters (NSP) and 574 men with abnormal sperm parameters (ASP), according to the World Health Organization sperm assessment references values established in 2010, were enrolled. Conventional sperm parameters were evaluated in all patients. Sperm static oxido-reduction potential (sORP) was assessed using the MiOXSYS. Sperm DNA integrity was measured in 604 patients. To ensure that sperm concentration was not a confounding factor in the sORP index ratio, sperm and seminal fluid sORP from 57 randomly selected additional patients were also measured using the MiOXSYS. sORP index (mV/106 sperm/mL) was higher in patients with ASP and seemed to correlate with conventional sperm parameters. Although receiver-operating characteristic analysis revealed that a sORP index cut-off of 0.79 could differentiate normal from ASP with 57.7% sensitivity and 73.1% specificity, these values are much lower than those found in the literature. These values also need to be higher to be applicable in a clinical setting. Furthermore, absolute sORP (mV) was not different in the presence or absence of spermatozoa. sORP index relationships with sperm parameters seem rather be due to sperm concentration, denominator of the sORP index ratio. The establishment of a reliable method using the absolute sORP value, independent of sperm concentration, needs to be addressed. Other oxidative stress biomarkers could be used to validate this method.Lay summaryThe World Health Organization (WHO) has recognized that oxidative stress may have a role in male infertility. Oxidative stress happens when there is an imbalance between the production of molecules containing oxygen and the antioxidants, molecules that neutralize the molecules containing oxygen. The molecules containing oxygen can cause damage to sperm DNA. This damage can be measured using a particular index and this study looked at whether the concentration of the sperm sample might have an impact on results and suggests this should be taken into consideration by clinicians and researchers.

Project description:ImportanceIn older adults with multiple serious comorbidities and functional limitations, the harms of intensive glycemic control likely exceed the benefits.ObjectivesTo examine glycemic control levels among older adults with diabetes mellitus by health status and to estimate the prevalence of potential overtreatment of diabetes.Design, setting, and participantsCross-sectional analysis of the data on 1288 older adults (≥65 years) with diabetes from the National Health and Nutrition Examination Survey (NHANES) from 2001 through 2010 who had a hemoglobin A1c (HbA1c) measurement. All analyses incorporated complex survey design to produce nationally representative estimates.ExposuresHealth status categories: very complex/poor, based on difficulty with 2 or more activities of daily living or dialysis dependence; complex/intermediate, based on difficulty with 2 or more instrumental activities of daily living or presence of 3 or more chronic conditions; and relatively healthy if none of these were present.Main outcomes and measuresTight glycemic control (HbA1c level, <7%) and use of diabetes medications likely to result in hypoglycemia (insulin or sulfonylureas).ResultsOf 1288 older adults with diabetes, 50.7% (95% CI, 46.6%-54.8%), representing 3.1 million (95% CI, 2.7-3.5), were relatively healthy, 28.1% (95% CI, 24.8%-31.5%), representing 1.7 million (95% CI, 1.4-2.0), had complex/intermediate health, and 21.2% (95% CI, 18.3%-24.4%), representing 1.3 million (95% CI, 1.1-1.5), had very complex/poor health. Overall, 61.5% (95% CI, 57.5%-65.3%), representing 3.8 million (95% CI, 3.4-4.2), had an HbA1c level of less than 7%; this proportion did not differ across health status categories (62.8% [95% CI, 56.9%-68.3%]) were relatively healthy, 63.0% (95% CI, 57.0%-68.6%) had complex/intermediate health, and 56.4% (95% CI, 49.7%-62.9%) had very complex/poor health (P = .26). Of the older adults with an HbA1c level of less than 7%, 54.9% (95% CI, 50.4%-59.3%) were treated with either insulin or sulfonylureas; this proportion was similar across health status categories (50.8% [95% CI, 45.1%-56.5%] were relatively healthy, 58.7% [95% CI, 49.4%-67.5%] had complex/intermediate health, and 60.0% [95% CI, 51.4%-68.1%] had very complex/poor health; P = .14). During the 10 study years, there were no significant changes in the proportion of older adults with an HbA1c level of less than 7% (P = .34), the proportion with an HbA1c level of less than 7% who had complex/intermediate or very complex/poor health (P = .27), or the proportion with an HbA1c level of less than 7% who were treated with insulin or sulfonylureas despite having complex/intermediate or very complex/poor health (P = .65).Conclusions and relevanceAlthough the harms of intensive treatment likely exceed the benefits for older patients with complex/intermediate or very complex/poor health status, most of these adults reached tight glycemic targets between 2001 and 2010. Most of them were treated with insulin or sulfonylureas, which may lead to severe hypoglycemia. Our findings suggest that a substantial proportion of older adults with diabetes were potentially overtreated.

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Low reduction potential of Ero1alpha regulatory disulphides ensures tight control of substrate oxidation.

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Low reduction potential of Ero1alpha regulatory disulphides ensures tight control of substrate oxidation.

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