Evidence for an Allosteric S-Nitrosoglutathione Binding Site in S-Nitrosoglutathione Reductase (GSNOR).

Current research has identified S-nitrosoglutathione reductase (GSNOR) as the central enzyme for regulating protein S-nitrosylation. In addition, the dysregulation of GSNOR expression is implicated in several organ system pathologies including respiratory, cardiovascular, hematologic, and neurologic, making GSNOR a primary target for pharmacological intervention. This study demonstrates the kinetic activation of GSNOR by its substrate S-nitrosoglutathione (GSNO). GSNOR kinetic analysis data resulted in nonhyperbolic behavior that was successfully accommodated by the Hill-Langmuir equation with a Hill coefficient of +1.75, indicating that the substrate, GSNO, was acting as a positive allosteric affector. Docking and molecular dynamics simulations were used to predict the location of the GSNO allosteric domain comprising the residues Asn185, Lys188, Gly321, and Lys323 in the vicinity of the structural Zn2+-binding site. GSNO binding to Lys188, Gly321, and Lys323 was further supported by hydrogen-deuterium exchange mass spectroscopy (HDXMS), as deuterium exchange significantly decreased at these residues in the presence of GSNO. The site-directed mutagenesis of Lys188Ala and Lys323Ala resulted in the loss of allosteric behavior. Ultimately, this work unambiguously demonstrates that GSNO at large concentrations activates GSNOR by binding to an allosteric site comprised of the residues Asn185, Lys188, Gly321, and Lys323. The identification of an allosteric GSNO-binding domain on GSNOR is significant, as it provides a platform for pharmacological intervention to modulate the activity of this essential enzyme.

O-Aminobenzoyl-S-nitrosoglutathione: A fluorogenic, cell permeable, pseudo-substrate for S-nitrosoglutathione reductase.

S-nitrosoglutathione reductase (GSNOR) is a multifunctional enzyme. It can catalyze NADH-dependent reduction of S-nitrosoglutathione (GSNO); as well as NAD+-dependent oxidation of hydroxymethylglutathione (HMGSH; an adduct formed by the spontaneous reaction between formaldehyde and glutathione). While initially recognized as the enzyme that is involved in formaldehyde detoxification, increasing amount of evidence has shown that GSNOR also plays a significant role in nitric oxide mediated signaling through its modulation of protein S-nitrosothiol signaling. In humans, GSNOR/S-nitrosothiols have been implicated in the etiology of several diseases including lung cancer, cystic fibrosis, asthma, pulmonary hypertension, and neuronal dysfunction. Currently, it is not possible to monitor the activity of GSNOR in live cells. In this article, we present a new compound, O-aminobenzoyl-S-nitrosoglutathione (OAbz-GSNO), which acts as a fluorogenic pseudo-substrate for GSNOR with an estimated Km value of 320µM. The weak OAbz-GSNO fluorescence increases by approximately 14 fold upon reduction of its S-NO moiety. In live cell imaging studies, OAbz-GSNO is readily taken up by primary pulmonary endothelial cells and localizes to the same perinuclear region as GSNOR. The perinuclear OAbz-GSNO fluorescence increases in a time dependent manner and this increase in fluorescence is abolished by siRNA knockdown of GSNOR or by treatment with GSNOR-specific inhibitors N6022 and C3. Taken together, these data demonstrate that OAbz-GSNO can be used as a tool to monitor the activity of GSNOR in live cells.

Combined detection of plasma GATA5 and SFRP2 methylation is a valid noninvasive biomarker for colorectal cancer and adenomas.

AIM: To investigate GATA5, SFRP2, and ITGA4 methylation in plasma DNA as noninvasive biomarkers for colorectal cancer (CRC) or adenomas. METHODS: There were 57 CRC patients, 30 adenomas patients, and 47 control patients enrolled in this study. Methylation-specific polymerase chain reaction was used to determine the promoter methylation status of GATA5, SFRP2, and ITGA4 genes in plasma DNA, and their association with clinical outcome in CRC. The predictive ability of GATA5, SFRP2, and ITGA4 methylation, individually or in combination, to detect CRC or adenomas was further analyzed. RESULTS: Hypermethylated GATA5 was detected in plasma in 61.4% (35/57) of CRC cases, 43.33% (13/30) of adenoma cases, and 21.28% (10/47) of control cases. The hypermethylation of SFRP2 was detected in 54.39% (31/57), 40.00% (12/30), and 27.66% (13/47) in plasma samples from CRC, adenomas, and controls, respectively. ITGA4 methylation was detected in 36.84% (21/57) of plasma samples of CRC patients and in 30.00% (9/30) of plasma samples from patients with colorectal adenomas, and the specificity of this individual biomarker was 80.85% (9/47). Moreover, GATA5 methylation in the plasma was significantly correlated with larger tumor size (P = 0.019), differentiation status (P = 0.038), TNM stage (P = 0.008), and lymph node metastasis (P = 0.008). SFRP2 and ITGA4 methylation in plasma significantly correlated with differentiation status (SFRP2, P = 0.012; ITGA4, P = 0.007), TNM stage (SFRP2, P = 0.034; ITGA4, P = 0.021), and lymph node metastasis (SFRP2, P = 0.034; ITGA4, P = 0.021). From the perspective of predictive power and cost-performance, using GATA5 and SFRP2 together as methylation markers seemed the most favorable predictor for CRC (OR = 8.06; 95%CI: 2.54-25.5; P < 0.01) and adenomas (OR = 3.35; 95%CI: 1.29-8.71; P = 0.012). CONCLUSION: A combination of GATA5 and SFRP2 methylation could be promising as a marker for the detection and diagnosis of CRC and adenomas.

[Raman spectroscopic characteristics of different rank coals and the relation with XRD structural parameters].

The Raman spectroscopic analysis for eleven different rank coals (57.58% to 94.01% of Cdaf, %) indicated that two distinct bands, i.e., D band (1340-1380 cm(-1)) and G band (1580-1600 cm(-1)), exist in the first order of Raman spectra, with the former being broader and the latter rather sharp. As the two bands were overlapped each other, each spectrum was fitted with two Lorentz peaks and the Raman information about position, intensity and FWHM of each band was thus obtained. The relation of these Raman parameters with Cdaf% showed that with the increase in C%, the position of D band and G band shifts to lower and higher frequency, respectively; the separation of the two band positions increases with the increase in C%; FWHM-D, FWHM-G and I(D)/I(G) have linear relationship with Cdaf% in the range of Cdaf% 75%-94%. The coal structural parameters, d002 and Lc from XRD are related with the position and FWHM of G band; the comparison of La from XRD and both from the Cancado and the KW equation indicated that the values from Cancado and the KW equation are unreasonable.