Case report of high-dose hydroxocobalamin in the treatment of vasoplegic syndrome during liver transplantation

A 66-year-old man with cryptogenic cirrhosis secondary to nonalcoholic steatohepatitis presented for orthotopic liver transplantation. Following organ reperfusion, the patient developed vasoplegic syndrome, with arterial blood pressures of approximately 60-70/30-40 mm Hg (mean arterial pressure [MAP] <45 mm Hg) for >90 minutes. He required high-dose norepinephrine and vasopressin infusions, as well as i.v. bolus doses of norepinephrine and vasopressin to reach a goal MAP> 60 mm Hg. There was minimal response to a 2 mg/kg i.v. bolus of methylene blue. Following the administration of 5 g of i.v.hydroxocobalamin, the patient had a profound improvement in arterial blood pressure, with subsequent discontinuation of the vasopressin infusion and rapid reduction of norepinephrine infusion from 20 to 2 μg/min. While there have been several reports of the efficacy of hydroxocobalamin for vasoplegia after cardiopulmonary bypass, there have been only limited cases of hydroxocobalamin used in liver transplantation, and none with high-dose administration. We present a case of vasoplegic syndrome during liver transplantation that was refractory to high-dose vasopressors and methylene blue but responsive to high-dose i.v. hydroxocobalamin.

[Association between long term systolic blood pressure variability index and cognitive function in middle-aged and elderly people]

OBJECTIVE

To investigate the association between different long term systolic blood pressure variability (SBPV) and cognitive function in middle-aged and elderly people.

METHODS

A total of 101 510 employees from the Tangshan Kailuan Group participated in the 2006-2007 annual physical examination, 5 440 cases were selected by simple randomly sampling method. After excluding participants who did not underwent 2012-2013 examination and without complete blood pressure and mini-mental state examination (MMSE) score, 3 002 participants (1 627 males, (50.86±9.93) years old) with integrated data were included into the study. The long term SBPV was calculated by standard deviation(SD), maximum-minimum difference(MMD), average real variability (ARV) of mean systolic blood pressure measured in 2006-2007, 2008-2009, 2010-2011 and 2012-2013. Participants were grouped by the quartile of the different SBPV index. Multiple linear regressions analysis was used to analyze the correlation between the long term SBPV and cognitive function status.

RESULTS

(1) The score of MMSE was 28.03±2.65. (2) The observation population was divided into four groups according to quartiles of different SBPV, respectively. The MMSE scores of SD<5.53 mmHg (1 mmHg=0.133 kPa)group, SD 5.53-8.90 mmHg group, SD 8.91-12.79 mmHg group and SD>12.79 mmHg group were 28.21±2.18, 28.26±3.09, 28.10±2.40 and 27.56±2.79, respectively(P<0.05). The MMSE scores of MMD<12.00 mmHg group, MMD 12.00-20.00 mmHg group, MMD 20.01-30.00 mmHg group and MMD>30.00 mmHg were 28.27±2.17, 28.25±3.09, 27.99±2.42 and 27.49±2.81, respectively(P<0.05). The MMSE scores of ARV<6.67 mmHg group, ARV 6.67-10.22 mmHg group, ARV 10.23-15.56 mmHg group and ARV>15.56 mmHg group were 28.27±2.20、28.28±3.20、28.00±2.42、27.57±2.65, respectively(P<0.05). (3) Adjusted for age, gender, baseline systolic blood pressure, body weight index, total cholesterol, fasting blood glucose, triglyceride, C reactive protein, smoke, drink, physical activity , the step-wise regressions analysis showed that SD(B=-0.129, P<0.05), MMD(B=-0.131, P<0.05), ARV(B=-0.125, P<0.05) had significant negative linear relationship with the MMSE score in the objects not taking the anti-hypertension drugs, and SD(B=-0.329, P<0.05), MMD(B=-0.314, P<0.05), but not ARV(B=-0.233, P>0.05), had significant negative linear relationship with the MMSE score in the objects taking the anti-hypertension drugs.

CONCLUSION

The long term SBPV indexes (SD, MMD, ARV ) are negatively correlated with the MMSE score in middle-aged and elderly people not taking the anti-hypertension drugs, and SD, MMD are negatively correlated with the MMSE score in people taking the anti-hypertension drugs. Clinical Trail Registry: Chinese Clinical Trail Registry, ChiCTRTNC-11001489.

[Influencing factors of orthostatism brachial-ankle pulse wave velocity and ankle brachial index in the elderly]

OBJECTIVE

To investigate the distribution and influencing factors of orthostatism brachial-ankle pulse wave velocity(baPWV) and ankle brachial index(ABI) in the elderly.

METHODS

Participants were selected with random sampling from ≥60 years old retired workers, who underwent 2010 to 2011 health check-up in the Tangshan Kailuan Hospital, Kailuan Linxi Hospital, Kailuan Zhaogezhuang Hospital. Multivariate linear regression analysis was used to analyze the influencing factors of orthostatism and supine baPWV and ABI in the elderly.

RESULTS

(1) A total of 2 464 participants were included, and 1 601 participants (1 065 males(66.5%) and (67.5±6.1) years old) with integral data were analyzed. Orthostatism baPWV was (3 885.4±1 503.5)cm/s and Supine baPWV was (1 761.2±371.4)cm/s.Orthostatism ABI was 1.54±0.21 and supine ABI was 1.10±0.12. Orthostatism baPWV increased with increasing age, while orthostatism ABI decreased with aging(trend test, both P<0.01)in <65, 65-69, 70-74, and ≥75 years old participants.(2) Multiple linear regression analysis showed that the age(β=0.19, P<0.01), lower limbs orthostatism systolic blood pressure(β=0.18, P<0.01), lower limbs supine systolic blood pressure (β=0.14, P<0.01), orthostatism heart rate (β=0.30, P<0.01), supine heart rate (β=0.23, P<0.01), body mass index (β=-0.18, P<0.01) were associated with orthostatism baPWV, and female(β=-0.055, P=0.01), upper limb orthostatism systolic blood pressure (β=-0.834, P<0.01), lower limbs orthostatism systolic blood pressure (β=0.708, P<0.01), lower limbs supine systolic blood pressure (β=0.099, P<0.01) and fasting blood glucose(β=-0.085, P<0.01) were associated with orthostatism ABI.

CONCLUSIONS

Orthostatism baPWV and ABI were significantly higher than those of supine's. Age, lower limbs orthostatism and supine systolic blood pressure, orthostatism and supine heart rate, body mass index were associated with orthostatism baPWV. Female, upper limb orthostatism systolic blood pressure, lower limbs orthostatism, supine systolic blood pressure and fasting blood glucose were associated with orthostatism ABI in the elderly.

Common polygenic variation and risk for childhood-onset schizophrenia

Childhood-onset schizophrenia (COS) is a rare and severe form of the disorder, with more striking abnormalities with respect to prepsychotic developmental disorders and abnormities in the brain development compared with later-onset schizophrenia. We previously documented that COS patients, compared with their healthy siblings and with adult-onset patients (AOS), carry significantly more rare chromosomal copy number variations, spanning large genomic regions (>100 kb) (Ahn et al. 2014). Here, we interrogated the contribution of common polygenic variation to the genetic susceptibility for schizophrenia. We examined the association between a direct measure of genetic risk of schizophrenia in 130 COS probands and 103 healthy siblings. Using data from the schizophrenia and autism GWAS of the Psychiatric Genomic Consortia, we selected three risk-related sets of single nucleotide polymorphisms from which we conducted polygenic risk score comparisons for COS probands and their healthy siblings. COS probands had higher genetic risk scores of both schizophrenia and autism than their siblings (P<0.05). Given the small sample size, these findings suggest that COS patients have more salient genetic risk than do AOS.

LAMC2 enhances the metastatic potential of lung adenocarcinoma

Lung cancer is the number one cancer killer, and metastasis is the main cause of high mortality in lung cancer patients. However, mechanisms underlying the development of lung cancer metastasis remain unknown. Using genome-wide transcriptional analysis in an experimental metastasis model, we identified laminin γ2 (LAMC2), an epithelial basement membrane protein, to be significantly upregulated in lung adenocarcinoma metastatic cells. Elevated LAMC2 increased traction force, migration, and invasion of lung adenocarcinoma cells accompanied by the induction of epithelial-mesenchymal transition (EMT). LAMC2 knockdown decreased traction force, migration, and invasion accompanied by EMT reduction in vitro, and attenuated metastasis in mice. LAMC2 promoted migration and invasion via EMT that was integrin β1- and ZEB1-dependent. High LAMC2 was significantly correlated with the mesenchymal marker vimentin expression in lung adenocarcinomas, and with higher risk of recurrence or death in patients with lung adenocarcinoma. We suggest that LAMC2 promotes metastasis in lung adenocarcinoma via EMT and may be a potential therapeutic target.

Genetic analysis of adiponectin variation and its association with type 2 diabetes in African Americans

OBJECTIVE

Adiponectin is an adipocytokine that has been implicated in a variety of metabolic disorders, including T2D and cardiovascular disease. Studies evaluating genetic variants in ADIPOQ have been contradictory when testing association with T2D in different ethnic groups.

DESIGN AND METHODS

In this study, 18 SNPs in ADIPOQ were tested for association with plasma adiponectin levels and diabetes status. SNPs were examined in two independent African-American cohorts (nmax = 1,116) from the Insulin Resistance Atherosclerosis Family Study (IRASFS) and the African American-Diabetes Heart Study (AA-DHS).

RESULTS

Five polymorphisms were nominally associated with plasma adiponectin levels in the meta-analysis (P = 0.035-1.02 × 10(-6) ) including a low frequency arginine to cysteine mutation (R55C) which reduced plasma adiponectin levels to <15% of the mean. Variants were then tested for association with T2D in a meta-analysis of these and the Wake Forest T2D case-control study (n = 3,233 T2D, 2645 non-T2D). Association with T2D was not observed (P ≥ 0.08), suggesting limited influence of ADIPOQ variants on T2D risk.

CONCLUSIONS

Despite identification of variants associated with adiponectin levels, a detailed genetic analysis of ADIPOQ revealed no association with T2D risk. This puts into question the role of adiponectin in T2D pathogenesis: whether low adiponectin levels are truly causal for or rather a consequence.

Primary irritation index and safety zone of cosmetics: retrospective analysis of skin patch tests in 7440 Korean women during 12 years

BACKGROUND

Cosmetics are products used over long periods by the public, and their safety is very important. Several types of human tests are used widely for the evaluation of cosmetics including single patch tests, in-use tests, human repeated insult patch test (HRIPT). However, there is no clear and well-defined published objective and standardized criteria for primary skin irritation in regard to the large variety of cosmetic products.

METHODS

This study analysed human patch tests conducted from May 2001 to December 2012 with 4606 materials of prototype or finished cosmetic products on 7440 normal Korean women aged 18-60 years. The tested products were patched under occlusion for 24 or 48 h, and skin tolerance was assessed twice at 30 min and 24 h after patch removal using a 5-step scale according to the CTFA guidelines.

RESULTS

Human patch tests for cosmetics were performed of 4606 cases, and 30-33 subjects participated in each case. The response in each case was calculated based on total subject number, skin reaction intensity and the number of respondents. The calculated response was standardized using the z-score, and a safety zone was provided in terms of human primary irritation in accordance with the human skin reaction evaluation criteria and usage or formula of cosmetics.

CONCLUSIONS

This study established the safety criteria for irritation in the cosmetics field.

Variants in adiponectin signaling pathway genes show little association with subclinical CVD in the diabetes heart study

OBJECTIVE

Understanding the interplay between adiposity, inflammation, and cardiovascular complications in type 2 diabetes mellitus (T2DM) remains a challenge. Signaling from adipocytes is considered important in this context. Adiponectin is the most abundant adipocytokine and has been associated with various measures of cardiovascular disease (CVD). This study examines the relationships between genetic variants in the adiponectin (ADIPOQ) and adiponectin-related signaling pathway genes and measures of subclinical CVD (vascular calcified plaque and carotid intima-media thickness), plasma lipids, and inflammation in T2DM.

DESIGN AND METHODS

Single-nucleotide polymorphisms (SNPs) in ADIPOQ (n = 45), SNPs tagging ADIPOR1 (n = 6), APIPOR2 (n = 8), APPL1 (n = 6) and known rare coding variants in KNG1 (n = 3) and LYZL1 (n = 3) were genotyped in 1220 European Americans from the family-based Diabetes Heart Study. Associations between SNPs and phenotypes of interest were assessed using a variance components analysis with adjustment for age, sex, T2DM-affected status, and body mass index.

RESULTS

There was minimal evidence of association between SNPs in the adiponectin signaling pathway genes and measures of calcified plaque; eight of the 71 SNPs showed evidence of association with subclinical CVD (P = 0.007-0.046) but not with other phenotypes examined. Nine additional SNPs were associated with at least one of the plasma lipid measures (P = 0.008-0.05).

CONCLUSION

Findings from this study do not support a significant role for variants in the adiponectin signaling pathway genes in contributing to risk for vascular calcification in T2DM. However, further understanding the interplay between adiposity, plasma lipids, and inflammation may prove important in the prediction and management of cardiovascular complications in T2DM.

Association between ADIPOQ SNPs with plasma adiponectin and glucose homeostasis and adiposity phenotypes in the IRAS Family Study

CONTEXT

Adiponectin is an adipocytokine associated with a variety of metabolic traits. These associations in human studies, in conjunction with functional studies in model systems, have implicated adiponectin in multiple metabolic processes.

OBJECTIVE

We hypothesize that genetic variants associated with plasma adiponectin would also be associated with glucose homeostasis and adiposity phenotypes.

DESIGN AND SETTING

The Insulin Resistance Atherosclerosis Family Study was designed to identify the genetic and environmental basis of insulin resistance and adiposity in the Hispanic- (n=1,424) and African-American (n=604) population.

MAIN OUTCOME MEASURES

High quality metabolic phenotypes, e.g. insulin sensitivity (S(I)), acute insulin response (AIR), disposition index (DI), fasting glucose, body mass index (BMI), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and waist circumference, were explored.

RESULTS

Based on association analysis of more than 40 genetic polymorphisms in the adiponectin gene (ADIPOQ), we found no consistent association of ADIPOQ variants with plasma adiponectin levels and adiposity phenotypes. However, there were two promoter variants, rs17300539 and rs822387, associated with plasma adiponectin levels (P=0.0079 and 0.021, respectively) in the Hispanic-American cohort that were also associated with S(I) (P=0.0067 and 0.013, respectively). In contrast, there was only a single promoter SNP, rs17300539, associated with plasma adiponectin levels (P=0.0018) and fasting glucose (P=0.042) in the African-American cohort. Strikingly, high impact coding variants did not show evidence of association.

CONCLUSIONS

The lack of consistent patterns of association between variants, adiponectin levels, glucose homeostasis, and adiposity phenotypes suggests a reassessment of the influence of adiponectin in these pathways.

The GPCR OGR1 (GPR68) mediates diverse signalling and contraction of airway smooth muscle in response to small reductions in extracellular pH

BACKGROUND AND PURPOSE

Previous studies have linked a reduction in pH in airway, caused by either environmental factors, microaspiration of gastric acid or inflammation, with airway smooth muscle (ASM) contraction and increased airway resistance. Neural mechanisms have been shown to mediate airway contraction in response to reductions in airway pH to < 6.5; whether reduced extracellular pH (pHo) has direct effects on ASM is unknown.

EXPERIMENTAL APPROACH

Intracellular signalling events stimulated by reduced pHo in human cultured ASM cells were examined by immunoblotting, phosphoinositide hydrolysis and calcium mobilization assays. ASM cell contractile state was examined using magnetic twisting cytometry. The expression of putative proton-sensing GPCRs in ASM was assessed by real-time PCR. The role of ovarian cancer G protein-coupled receptor 1 (OGR1 or GPR68) in acid-induced ASM signalling and contraction was assessed in cultures subjected to siRNA-mediated OGR1 knockdown.

KEY RESULTS

ASM cells responded to incremental reductions in pHo (from pH 8.0 to pH 6.8) by activating multiple signalling pathways, involving p42/p44, PKB, PKA and calcium mobilization. Coincidently, ASM cells contracted in response to decreased pHo with similar 'dose'-dependence. Real-time PCR suggested OGR1 was the only proton-sensing GPCR expressed in ASM cells. Both acid-induced signalling (with the exception of PKB activation) and contraction were significantly attenuated by knockdown of OGR1.

CONCLUSIONS AND IMPLICATIONS

These studies reveal OGR1 to be a physiologically relevant GPCR in ASM cells, capable of pleiotropic signalling and mediating contraction in response to small reductions in extracellular pH. Accordingly, ASM OGR1 may contribute to asthma pathology and represent a therapeutic target in obstructive lung diseases.

Estimating the contributions of rare and common genetic variations and clinical measures to a model trait: adiponectin

Common genetic variation frequently accounts for only a modest amount of interindividual variation in quantitative traits and complex disease susceptibility. Circulating adiponectin, an adipocytokine implicated in metabolic disease, is a model for assessing the contribution of genetic and clinical factors to quantitative trait variation. The adiponectin locus, ADIPOQ, is the primary source of genetically mediated variation in plasma adiponectin levels. This study sought to define the genetic architecture of ADIPOQ in the comprehensively phenotyped Hispanic (n = 1,151) and African American (n = 574) participants from the Insulin Resistance Atherosclerosis Family Study (IRASFS). Through resequencing and bioinformatic analysis, rare/low frequency (<5% MAF) and common variants (>5% MAF) in ADIPOQ were identified. Genetic variants and clinical variables were assessed for association with adiponectin levels and contribution to adiponectin variance in the Hispanic and African American cohorts. Clinical traits accounted for the greatest proportion of variance (POV) at 31% (P = 1.16 × 10-(47)) and 47% (P = 5.82 × 10-(20)), respectively. Rare/low frequency variants contributed more than common variants to variance in Hispanics: POV = 18% (P = 6.40 × 10-(15)) and POV = 5% (P = 0.19), respectively. In African Americans, rare/low frequency and common variants both contributed approximately equally to variance: POV = 6% (P = 5.44 × 10-(12)) and POV = 9% (P = 1.44 × 10-(10)), respectively. Importantly, single low frequency alleles in each ethnic group were as important as, or more important than, common variants in explaining variation in adiponectin. Cumulatively, these clinical and ethnicity-specific genetic contributors explained half or more of the variance in Hispanic and African Americans and provide new insight into the sources of variation for this important adipocytokine.

Genetic risk assessment of type 2 diabetes-associated polymorphisms in African Americans

OBJECTIVE

Multiple single nucleotide polymorphisms (SNPs) associated with type 2 diabetes (T2D) susceptibility have been identified in predominantly European-derived populations. These SNPs have not been extensively investigated for individual and cumulative effects on T2D risk in African Americans.

RESEARCH DESIGN AND METHODS

Seventeen index T2D risk variants were genotyped in 2,652 African American case subjects with T2D and 1,393 nondiabetic control subjects. Individual SNPs and cumulative risk allele loads were assessed for association with risk for T2D. Cumulative risk was assessed by counting risk alleles and evaluating the difference in cumulative risk scores between case subjects and control subjects. A second analysis weighted risk scores (ln [OR]) based on previously reported European-derived effect sizes.

RESULTS

Frequencies of risk alleles ranged from 8.6 to 99.9%. Eleven SNPs had ORs >1, and 5 from ADAMTS9, WFS1, CDKAL1, JAZF1, and TCF7L2 trended or had nominally significant evidence of T2D association (P < 0.05). Individuals carried between 13 and 29 risk alleles. Association was observed between T2D and increase in risk allele load (unweighted OR 1.04 [95% CI 1.01-1.08], P = 0.010; weighted 1.06 [1.03-1.10], P = 8.10 × 10(-5)). When TCF7L2 SNP rs7903146 was included as a covariate, the risk score was no longer associated with T2D in either model (unweighted 1.02 [0.98-1.05], P = 0.33; weighted 1.02 [0.98-1.06], P = 0.40).

CONCLUSIONS

The trend of increase in risk for T2D with increasing risk allele load is similar to observations in European-derived populations; however, these analyses indicate that T2D genetic risk is primarily mediated through the effect of TCF7L2 in African Americans.

A genome-wide association search for type 2 diabetes genes in African Americans

African Americans are disproportionately affected by type 2 diabetes (T2DM) yet few studies have examined T2DM using genome-wide association approaches in this ethnicity. The aim of this study was to identify genes associated with T2DM in the African American population. We performed a Genome Wide Association Study (GWAS) using the Affymetrix 6.0 array in 965 African-American cases with T2DM and end-stage renal disease (T2DM-ESRD) and 1029 population-based controls. The most significant SNPs (n = 550 independent loci) were genotyped in a replication cohort and 122 SNPs (n = 98 independent loci) were further tested through genotyping three additional validation cohorts followed by meta-analysis in all five cohorts totaling 3,132 cases and 3,317 controls. Twelve SNPs had evidence of association in the GWAS (P<0.0071), were directionally consistent in the Replication cohort and were associated with T2DM in subjects without nephropathy (P<0.05). Meta-analysis in all cases and controls revealed a single SNP reaching genome-wide significance (P<2.5×10(-8)). SNP rs7560163 (P = 7.0×10(-9), OR (95% CI) = 0.75 (0.67-0.84)) is located intergenically between RND3 and RBM43. Four additional loci (rs7542900, rs4659485, rs2722769 and rs7107217) were associated with T2DM (P<0.05) and reached more nominal levels of significance (P<2.5×10(-5)) in the overall analysis and may represent novel loci that contribute to T2DM. We have identified novel T2DM-susceptibility variants in the African-American population. Notably, T2DM risk was associated with the major allele and implies an interesting genetic architecture in this population. These results suggest that multiple loci underlie T2DM susceptibility in the African-American population and that these loci are distinct from those identified in other ethnic populations.

Resequencing and analysis of variation in the TCF7L2 gene in African Americans suggests that SNP rs7903146 is the causal diabetes susceptibility variant

OBJECTIVE

Variation in the transcription factor 7-like 2 (TCF7L2) locus is associated with type 2 diabetes across multiple ethnicities. The aim of this study was to elucidate which variant in TCF7L2 confers diabetes susceptibility in African Americans.

RESEARCH DESIGN AND METHODS

Through the evaluation of tagging single nucleotide polymorphisms (SNPs), type 2 diabetes susceptibility was limited to a 4.3-kb interval, which contains the YRI (African) linkage disequilibrium (LD) block containing rs7903146. To better define the relationship between type 2 diabetes risk and genetic variation we resequenced this 4.3-kb region in 96 African American DNAs. Thirty-three novel and 13 known SNPs were identified: 20 with minor allele frequencies (MAF) >0.05 and 12 with MAF >0.10. These polymorphisms and the previously identified DG10S478 microsatellite were evaluated in African American type 2 diabetic cases (n = 1,033) and controls (n = 1,106).

RESULTS

Variants identified from direct sequencing and databases were genotyped or imputed. Fifteen SNPs showed association with type 2 diabetes (P < 0.05) with rs7903146 being the most significant (P = 6.32 × 10(-6)). Results of imputation, haplotype, and conditional analysis of SNPs were consistent with rs7903146 being the trait-defining SNP. Analysis of the DG10S478 microsatellite, which is outside the 4.3-kb LD block, revealed consistent association of risk allele 8 with type 2 diabetes (odds ratio [OR] = 1.33; P = 0.022) as reported in European populations; however, allele 16 (MAF = 0.016 cases and 0.032 controls) was strongly associated with reduced risk (OR = 0.39; P = 5.02 × 10(-5)) in contrast with previous studies.

CONCLUSIONS

In African Americans, these observations suggest that rs7903146 is the trait-defining polymorphism associated with type 2 diabetes risk. Collectively, these results support ethnic differences in type 2 diabetes associations.

A genome-wide association study for diabetic nephropathy genes in African Americans

A genome-wide association study was performed using the Affymetrix 6.0 chip to identify genes associated with diabetic nephropathy in African Americans. Association analysis was performed adjusting for admixture in 965 type 2 diabetic African American patients with end-stage renal disease (ESRD) and in 1029 African Americans without type 2 diabetes or kidney disease as controls. The top 724 single nucleotide polymorphisms (SNPs) with evidence of association to diabetic nephropathy were then genotyped in a replication sample of an additional 709 type 2 diabetes-ESRD patients and 690 controls. SNPs with evidence of association in both the original and replication studies were tested in additional African American cohorts consisting of 1246 patients with type 2 diabetes without kidney disease and 1216 with non-diabetic ESRD to differentiate candidate loci for type 2 diabetes-ESRD, type 2 diabetes, and/or all-cause ESRD. Twenty-five SNPs were significantly associated with type 2 diabetes-ESRD in the genome-wide association and initial replication. Although genome-wide significance with type 2 diabetes was not found for any of these 25 SNPs, several genes, including RPS12, LIMK2, and SFI1 are strong candidates for diabetic nephropathy. A combined analysis of all 2890 patients with ESRD showed significant association SNPs in LIMK2 and SFI1 suggesting that they also contribute to all-cause ESRD. Thus, our results suggest that multiple loci underlie susceptibility to kidney disease in African Americans with type 2 diabetes and some may also contribute to all-cause ESRD.

Molecular basis of a linkage peak: exome sequencing and family-based analysis identify a rare genetic variant in the ADIPOQ gene in the IRAS Family Study

Family-based linkage analysis has been a powerful tool for identification of genes contributing to traits with monogenic patterns of inheritance. These approaches have been of limited utility in identification of genes underlying complex traits. In contrast, searches for common genetic variants associated with complex traits have been highly successful. It is now widely recognized that common variations frequently explain only part of the inter-individual variation in populations. 'Rare' genetic variants have been hypothesized to contribute significantly to phenotypic variation in the population. We have developed a combination of family-based linkage, whole-exome sequencing, direct sequencing and association methods to efficiently identify rare variants of large effect. Key to the successful application of the method was the recognition that only a few families in a sample contribute significantly to a linkage signal. Thus, a search for mutations can be targeted to a small number of families in a chromosome interval restricted to the linkage peak. This approach has been used to identify a rare (1.1%) G45R mutation in the gene encoding adiponectin, ADIPOQ. This variant explains a strong linkage signal (LOD > 8.0) and accounts for ∼17% of the variance in plasma adiponectin levels in a sample of 1240 Hispanic Americans and 63% of the variance in families carrying the mutation. Individuals carrying the G45R mutation have mean adiponectin levels that are 19% of non-carriers. We propose that rare variants may be a common explanation for linkage peaks observed in complex trait genetics. This approach is applicable to a wide range of family studies and has potential to be a discovery tool for identification of novel genes influencing complex traits.

A whole genome association study of neuroticism using DNA pooling

We describe a multistage approach to identify single nucleotide polymorphisms (SNPs) associated with neuroticism, a personality trait that shares genetic determinants with major depression and anxiety disorders. Whole genome association with 452 574 SNPs was performed on DNA pools from approximately 2000 individuals selected on extremes of neuroticism scores from a cohort of 88 142 people from southwest England. The most significant SNPs were then genotyped on independent samples to replicate findings. We were able to replicate association of one SNP within the PDE4D gene in a second sample collected by our laboratory and in a family-based test in an independent sample; however, the SNP was not significantly associated with neuroticism in two other independent samples. We also observed an enrichment of low P-values in known regions of copy number variations. Simulation indicates that our study had approximately 80% power to identify neuroticism loci in the genome with odds ratio (OR)>2, and approximately 50% power to identify small effects (OR=1.5). Since we failed to find any loci accounting for more than 1% of the variance, the heritability of neuroticism probably arises from many loci each explaining much less than 1%. Our findings argue the need for much larger samples than anticipated in genetic association studies and that the biological basis of emotional disorders is extremely complex.

Association between glutamic acid decarboxylase genes and anxiety disorders, major depression, and neuroticism

Abnormalities in the gamma-aminobutyric acid (GABA) neurotransmitter system have been noted in subjects with mood and anxiety disorders. Glutamic acid decarboxylase (GAD) enzymes synthesize GABA from glutamate, and, thus, are reasonable candidate susceptibility genes for these conditions. In this study, we examined the GAD1 and GAD2 genes for their association with genetic risk across a range of internalizing disorders. We used multivariate structural equation modeling to identify common genetic risk factors for major depression, generalized anxiety disorder, panic disorder, agoraphobia, social phobia and neuroticism (N) in a sample of 9270 adult subjects from the population-based Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. One member from each twin pair for whom DNA was available was selected as a case or control based on scoring at the extremes of the genetic factor extracted from the analysis. The resulting sample of 589 cases and 539 controls was entered into a two-stage association study in which candidate loci were screened in stage 1, the positive results of which were tested for replication in stage 2. Several of the six single-nucleotide polymorphisms tested in the GAD1 region demonstrated significant association in both stages, and a combined analysis in all 1128 subjects indicated that they formed a common high-risk haplotype that was significantly over-represented in cases (P=0.003) with effect size OR=1.23. Out of 14 GAD2 markers screened in stage 1, only one met the threshold criteria for follow-up in stage 2. This marker, plus three others that formed significant haplotype combinations in stage 1, did not replicate their association with the phenotype in stage 2. Subject to confirmation in an independent sample, our study suggests that variations in the GAD1 gene may contribute to individual differences in N and impact susceptibility across a range of anxiety disorders and major depression.

Mechanical signals and mechanosensitive modulation of intracellular [Ca(2+)] in smooth muscle

We tested the hypothesis that strain is the primary mechanical signal in the mechanosensitive modulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in airway smooth muscle. We found that [Ca(2+)](i) was significantly correlated with muscle length during isotonic shortening against 20% isometric force (F(iso)). When the isotonic load was changed to 50% F(iso), data points from the 20 and 50% F(iso) experiments overlapped in the length-[Ca(2+)](i) relationship. Similarly, data points from the 80% F(iso) experiments clustered near those from the 50% F(iso) experiments. Therefore, despite 2.5- and 4-fold differences in external load, [Ca(2+)](i) did not deviate much from the length-[Ca(2+)](i) relation that fitted the 20% F(iso) data. Maximal inhibition of sarcoplasmic reticular (SR) Ca(2+) uptake by 10 microM cyclopiazonic acid (CPA) did not significantly change [Ca(2+)](i) in carbachol-induced isometric contractions and isotonic shortening. CPA also did not significantly change myosin light-chain phosphorylation or force redevelopment when carbachol-activated muscle strips were quickly released from optimal length (L(o)) to 0.5 L(o). These results are consistent with the hypothesis and suggest that SR Ca(2+) uptake is not the underlying mechanism.

Mechanical strain modulates maximal phosphatidylinositol turnover in airway smooth muscle

Mechanical strain regulates the maximal level of myosin light chain phosphorylation mediated by muscarinic activation in airway smooth muscle. Accordingly, we tested the hypothesis that mechanical strain regulates maximal phosphatidylinositol (PI) turnover (V(max)) coupled to muscarinic receptors in bovine tracheal smooth muscle. We found that PI turnover was not significantly length dependent in unstimulated tissues. However, carbachol-induced PI turnover was linearly dependent on muscle length at both 1 and 100 microM. The observed linear length dependence of PI turnover at maximal carbachol concentration (100 microM) suggests that mechanical strain regulates V(max). When carbachol concentration-PI turnover relationships were measured at optimal length and at 20% optimal length, the results could be explained by changes in V(max) alone. To determine whether the length-dependent step is upstream from heterotrimeric G proteins, we investigated the length dependence of fluoroaluminate-induced PI turnover. The results indicate that fluoroaluminate-induced PI turnover remained significantly length dependent at maximal concentration. These findings together suggest that regulating functional units of G proteins and/or phospholipase C enzymes may be the primary mechanism of mechanosensitive modulation in airway smooth muscle.

The origin and evolution of green algal and plant actins

The Viridiplantae are subdivided into two groups: the Chlorophyta, which includes the Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Prasinophyceae; and the Streptophyta, which includes the Charophyceae and all land plants. Within the Streptophyta, the actin genes of the angiosperms diverge nearly simultaneously from each other before the separation of monocots and dicots. Previous evolutionary analyses have provided limited insights into the gene duplications that have produced these complex gene families. We address the origin and diversification of land plant actin genes by studying the phylogeny of actins within the green algae, ferns, and fern allies. Partial genomic sequences or cDNAs encoding actin were characterized from Cosmarium botrytis (Zygnematales), Selaginella apoda (Selaginellales), Anemia phyllitidis (Polypodiales), and Psilotum triquetrum (Psilotales). Selaginella contains at least two actin genes. One sequence (Ac2) diverges within a group of fern sequences that also includes the Psilotum Ac1 actin gene and one gymnosperm sequence (Cycas revoluta Cyc3). This clade is positioned outside of the angiosperm actin gene radiation. The second Selaginella sequence (Ac1) is the sister to all remaining land plant actin sequences, although the internal branches in this portion of the tree are very short. Use of complete actin-coding regions in phylogenetic analyses provides support for the separation of angiosperm actins into two classes. N-terminal "signature" sequence analyses support these groupings. One class (VEG) includes actin genes that are often expressed in vegetative structures. The second class (REP) includes actin genes that trace their ancestry within the vegetative actins and contains members that are largely expressed in reproductive structures. Analysis of intron positions within actin genes shows that sequences from both Selaginella and Cosmarium contain the conserved 20-3, 152-1, and 356-3 introns found in many members of the Streptophyta. In addition, the Cosmarium actin gene contains a novel intron at position 76-1.

Actin phylogeny identifies Mesostigma viride as a flagellate ancestor of the land plants

Green algae and land plants trace their evolutionary history to a unique common ancestor. This "green lineage" is phylogenetically subdivided into two distinct assemblages, the Chlorophyta and the Streptophyta. The Chlorophyta includes the Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Prasinopohyceae, whereas the Streptophyta includes the Charophyceae plus the bryophytes, ferns, and all other multicellular land plants (Embryophyta). The Prasinophyceae is believed to contain the earliest divergences within the green lineage. Phylogenetic analyses using rDNA sequences identify the prasinophytes as a paraphyletic taxon that diverges at the base of the Chlorophyta. rDNA analyses, however, provide ambiguous results regarding the identity of the flagellate ancestor of the Streptophyta. We have sequenced the actin-encoding cDNAs from Scherffelia dubia (Prasinophyceae), Coleochaete scutata, Spirogyra sp. (Charophyceae), and the single-copy actin gene from Mesostigma viride (Prasinophyceae). Phylogenetic analyses show Mesostigma to be the earliest divergence within the Streptophyta and provide direct evidence for a scaly, biflagellate, unicellular ancestor for this lineage. This result is supported by the existence of two conserved actin-coding region introns (positions 20-3, 152-1), and one intron in the 5'-untranslated region of the actin gene shared by Mesostigma and the embryophytes.

Structural/functional properties of the Glu1-HSer57 N-terminal fragment of human plasminogen: conformational characterization and interaction with kringle domains

The Glu1-Val79 N-terminal peptide (NTP) domain of human plasminogen (Pgn) is followed by a tandem array of five kringle (K) structures of approximately 9 kDa each. K1, K2, K4, and K5 contain each a lysine-binding site (LBS). Pgn was cleaved with CNBr and the Glul-HSer57 N-terminal fragment (CB-NTP) isolated. In addition, the Ile27-Ile56 peptide (L-NTP) that spans the doubly S-S bridged loop segment of NTP was synthesized. Pgn kringles were generated either by proteolytic fragmentation of Pgn (K4, K5) or via recombinant gene expression (rK1, rK2, and rK3). Interactions of CB-NTP with each of the Pgn kringles were monitored by 1H-NMR at 500 MHz and values for the equilibrium association constants (Ka) determined: rK1, Ka approximately 4.6 mM(-1); rK2, Ka approximately 3.3 mM(-1); K4, Ka approximately 6.2 mM-'; K5, K, 2.3 mM(-1). Thus, the lysine-binding kringles interact with CB-NTP more strongly than with Nalpha-acetyl-L-lysine methyl ester (Ka < 0.6 mM(-l), which reveals specificity for the NTP. In contrast, CB-NTP does not measurably interact with rK3. which is devoid of a LBS. CB-NTP and L-NTP 1H-NMR spectra were assigned and interproton distances estimated from 1H-1H Overhauser (NOESY) experiments. Structures of L-NTP and the Glul-Ile27 segment of CB-NTP were computed via restrained dynamic simulated annealing/energy minimization (SA/EM) protocols. Conformational models of CB-NTP were generated by joining the two (sub)structures followed by a round of constrained SA/EM. Helical turns are indicated for segments 6-9, 12-16, 28-30, and 45-48. Within the Cys34-Cys42 loop of L-NTP, the structure of the Glu-Glu-Asp-Glu-Glu39 segment appears to be relatively less defined, as is the case for the stretch containing Lys5O within the Cys42-Cys54 segment, consistent with the latter possibly interacting with kringle domains in intact Glul-Pgn. Overall, the CB-NTP and L-NTP fragments are of low regular secondary structure content-as indicated by UV-CD spectra- and exhibit fast amide 1H-2H exchange in 2H2O, suggestive of high flexibility.

Lysine-50 is a likely site for anchoring the plasminogen N-terminal peptide to lysine-binding kringles

Interactions between the kringle 4 (K4) domain of human plasminogen (Pgn) and segments of the N-terminal Glu1-Lys77 peptide (NTP) have been investigated via 1H-NMR at 500 MHz. NTP peptide stretches devoid of Lys residues but carrying an internal Arg residue show negligible affinity toward K4 (equilibrium association constant Ka < 0.05 mM(-1)). In contrast, while most fragments containing an internal Lys residue exhibit affinities comparable to that shown by the blocked Lys derivative Nalpha-acetyl-L-lysine-methyl ester (Ka approximately 0.2 mM(-1), peptides encompassing Lys50O consistently show higher Ka values. Among the investigated linear peptides, Nalpha-acetyl-Ala-Phe-Tyr-His-Ser-Ser-Lys5O-Glu-Gln-NH2 (AcAFYHSK5OEQ-NH2) exhibits the strongest interaction with K4 (Ka approximately 1.4 mM(-1)), followed by AcYHSK50EQ-NH2 (Ka approximately 0.9 mM(-1)). Relative to the wild-type sequence, mutated hexapeptides exhibit lesser affinity for K4. When a Lys50 --> Ser mutation was introduced (==> AcYHSS50EQ-NH2), binding was abolished. The Ile27-lle56 construct (L-NTP) contains the Lys50 site within a loop constrained by two cystine bridges. The propensity of recombinant Pgn K1 (rK1) and K2 (rK2) modules, and of Pgn fragments encompassing the intact K4 and K5 domains, for binding L-NTP, was investigated. We find that L-NTP interacts with rK1, rK2, K4, and K5-all lysine-binding kringles-in a fashion that closely mimics what has been observed for the Glul-HSer57 N-terminal fragment of Pgn (CB-NTP). Thus, both the constellation of kringle lysine binding site (LBS) aromatic residues that are perturbed upon complexation of L-NTP and magnitudes of kringle-L-NTP binding affinities (rK1, Ka approximately 4.3 mM(-1); rK2, Ka approximately 3.7 mM(-1; K4, Ka approximately 6.4 mM(1); and K5, Ka approximately 2.1 mM(-1)) are essentially the same as for the corresponding kringle-CB-NTP pairs. Molecular modeling studies suggest that the Glu39-Lys50 stretch in NTP generates an area that complements, both topologically and electrostatically, the solvent-exposed kringle LBS surface.

Structural examination of the influence of phosphorylation on the binding of fibrinopeptide A to bovine thrombin

Upon addition of thrombin, fibrinopeptides A and B are cleaved off from the N-termini of four chains of fibrinogen (Aalpha Bbeta gamma)2, and sites of polymerization are exposed, resulting in formation of a fibrin clot. For the fibrinogen Aalpha chain, cleavage occurs most prevalently at the Arg16-Gly17 peptide bond. About 25-30% of the human fibrinogen Aalpha chains are phosphorylated in nature at the position of Ser3, but the function for this modification is not understood. Previous NMR studies indicated that the N-terminal portion (1ADSGE5) of unphosphorylated fibrinopeptide A does not interact with the surface of bovine thrombin. Kinetic and NMR studies have now been carried out to assess whether phosphorylation at Ser3 allows the N-terminal segment (1ADSGEGDFLAEGGGVR16) to become anchored on the thrombin surface, leading to formation of a catalytically more efficient enzyme-substrate complex. Kinetic results indicate that phosphorylation leads to an approximately 65% increase in substrate specificity (kcat/Km) toward hydrolysis of fibrinogen Aalpha(1-20). 31P NMR studies reveal that the phosphorylated group does interact with thrombin, and 1H line broadening studies suggest that phosphorylation does promote binding of amino acids 1-5. Two-dimensional transferred nuclear Overhauser effect spectroscopy studies of bound fibrinopeptide A(1-16 Ser3P) indicate that phosphorylation allows new through-space interactions involving amino acid residues 1ADSGE5 to be observed. Computational docking of the peptide onto the X-ray structure of thrombin suggests that the phosphate may interact with basic residues at the rim of the heparin binding site of thrombin. As a result, the phosphate may serve as an anionic linker between the fibrinopeptide and the enzyme thrombin.

Purification and characterization of a manganese-containing superoxide dismutase from a carboxydobacterium, Pseudomonas carboxydohydrogena

Superoxide dismutase from Pseudomonas carboxydohydrogena, a carboxydobacterium, grown on carbon monoxide was purified 37.6-fold in seven steps to homogeneity, with a yield of 1.4%. The final specific activity was 2,396 units per mg protein as determined by an assay based on a 50% decrease in the rate of cytochrome c reduction. The molecular weight of the native enzyme was determined to be 42,500. Sodium dodecyl sulfate gel electrophoresis revealed two identical subunits of molecular weight 21,700. The optimal pH for enzyme activity was found to be 9.0. The enzyme was stable to heat treatment. The isoelectric point of the native enzyme was found to be 7.1. The enzyme showed an absorption peak at 280 nm with a shoulder at around 289 nm. Sodium azide, but not sodium cyanide and hydrogen peroxide, was found to inhibit the enzyme activity. One mol of native enzyme was found to contain 1.09 g-atom of manganese. Analysis of amino acid composition revealed that the enzyme contains cysteine. The superoxide dismutase of P. carboxydohydrogena was found to have antigenic sites identical to those of Oligotropha carboxydovorans. The enzyme showed partial identity to Hydrogenophaga pseudoflava and Escherichia coli enzymes, but no identity to Acinetobacter sp. strain JC1 enzyme.

Ligand preferences of kringle 2 and homologous domains of human plasminogen: canvassing weak, intermediate, and high-affinity binding sites by 1H-NMR

The interaction of various small aliphatic and aromatic ionic ligands with the human plasminogen (HPg) recombinant kringle 2 (r-K2) domain has been investigated by 1H-NMR spectroscopy at 500 MHz. The results are compared against ligand-binding properties of the homologous, lysine-binding HPg kringle 1 (K1), kringle 4 (K4), and kringle 5 (K5). The investigated ligands include the omega-aminocarboxylic acids 4-aminobutyric acid (4-ABA), 5-aminopentanoic acid (5-APA), 6-aminohexanoic acid (6-AHA), 7-aminoheptanoic acid (7-AHA), lysine and arginine derivatives with free and blocked alpha-amino and/or carboxylate groups, and a number of cyclic analogs, zwitterions of similar size such as trans-(aminomethyl)cyclohexanecarboxylic acid (AMCHA) and p-benzylaminesulfonic acid (BASA), and the nonzwitterions benzylamine and benzamidine. Equilibrium association constant (Ka) values were determined from 1H-NMR ligand titration profiles. Among the aliphatic linear ligands, 5-APA (Ka approximately 3.4 mM-1) shows the strongest interaction with r-K2 followed by 6-AHA (Ka approximately 2.3 mM-1), 7-AHA (Ka approximately 0.45 mM-1), and 4-ABA (Ka approximately 0.22 mM-1). In contrast, r-K1, K4, and K5 exhibit a preference for 6-AHA (Ka approximately 74.2, 21.0, and 10.6 mM-1, respectively), a ligand approximately 1.14 A longer than 5-APA. Mutations R220G and E221D increase the affinity of r-K2 for these ligands but leave the selectivity profile essentially unaffected: 5-APA > 6-AHA > 7-AHA > 4-ABA (Ka approximately 6.5, 3.9, 1.8, and 0.74 mM-1, respectively). We find that, while r-K2 definitely interacts with Nalpha-acetyl-L-lysine and L-lysine (Ka approximately 0.96 and 0.68 mM-1, respectively), the affinity for analogs carrying a blocked carboxylate group is relatively weak (Ka approximately 0.1 mM-1). We also investigated the interaction of r-K2 with L-arginine (Ka approximately 0.31 mM-1) and its derivatives Nalpha-acetyl-L-arginine (Ka approximately 0.55 mM-1), Nalpha-acetyl-L-arginine methyl ester (Ka approximately 0.07 mM-1), and L-arginine methyl ester (Ka approximately 0.03 mM-1). Zwitterionic gamma-guanidinobutyric acid, containing one less methylene group than arginine, exhibits a Ka of approximately 0.28 mM-1. The affinity of r-K2 for lysine and arginine derivatives suggests that K2 could play a role in intermolecular as well as intramolecular interactions of HPg. As is the case for the HPg K1, K4, and K5, among the tested ligands, AMCHA is the one which interacts most firmly with r-K2 (Ka approximately 7.3 mM-1) while the aromatic ligands BASA, benzylamine, and benzamidine exhibit Ka values of approximately 4.0, approximately 0.04, and approximately 0.03 mM-1, respectively. The relative stability of these interactions indicates a strict requirement for both cationic and anionic polar groups in the ligand, whereas the presence of a lipophilic aromatic group seems to be of lesser consequence. Ligand-induced shifts of r-K2 (1)H-NMR signals and two-dimensional nuclear Overhauser effect (NOESY) experiments in the presence of 6-AHA reveal direct involvement of residues Tyr36, Trp62, Phe64, and Trp72 (kringle residue numbering convention) in ligand binding. Starting from the X-ray crystallographic structure of HPg K4 and the intermolecular 1H-NMR NOE data, two models of the K2 lysine binding site complexed to 6-AHA have been derived which differ mainly in the extent of electrostatic pairing between the K2 Arg56 and Glu57 side chains. Competition between these two conformations in equilibrium may account for the relatively lesser affinity of the K2 domain for zwitterionic lysine-type ligands.

Kringle 5 of plasminogen is a novel inhibitor of endothelial cell growth

Angiostatin is a potent angiogenesis inhibitor which has been identified as an internal fragment of plasminogen that includes its first four kringle modules. We have recently demonstrated that the anti-endothelial cell proliferative activity of angiostatin is also displayed by the first three kringle structures of plasminogen and marginally so by kringle 4 (Cao, Y., Ji, R.-W., Davidson, D., Schaller, J., Marti, D., Sohndel, S., McCance, S. G., O'Reilly, M. S. , Llinás, M., and Folkman, J. (1996) J. Biol. Chem. 271, 29461-29467). We now report that the kringle 5 fragment of human plasminogen is a specific inhibitor for endothelial cell proliferation. Kringle 5 obtained as a proteolytic fragment of human plasminogen displays potent inhibitory effect on bovine capillary endothelial cells with a half-maximal concentration (ED50) of approximately 50 nM. Thus, kringle 5 would appear to be more potent than angiostatin on inhibition of basic fibroblast growth factor-stimulated capillary endothelial cell proliferation. Appropriately folded recombinant mouse kringle 5 protein, expressed in Escherichia coli, exhibits a comparable inhibitory effect as the proteolytic kringle 5 fragment. Thus, kringle 5 domain of human plasminogen is a novel endothelial inhibitor that is sufficiently potent to block the growth factor-stimulated endothelial cell growth.

Ligand binding to the tissue-type plasminogen activator kringle 2 domain: structural characterization by 1H-NMR

Ligand binding to a recombinant human tissue-type plasminogen (tPA) kringle 2 domain has been characterized via 1H-NMR spectroscopy at 500 MHz. Seven omega-amino acid ligands were investigated: L-Lys, 6-aminohexanoic acid (6AHA), 7-aminoheptanoic acid (7AHA), trans-(aminomethyl)-cyclohexanecarboxylic acid (AMCHA), p-(aminomethyl)benzoic acid (PAMBA), p-(aminoethyl)benzoic acid (PAEBA), and p-benzylaminesulfonic acid (BASA). The interactions with two peptides containing a C-terminal lysyl residue, Tyr-Leu-Leu-Lys (YLLK) and Ala-Phe-Gln-Tyr-His-Ser-Lys (AFQYHSK), were also studied. The sequence AFQYHSK is found within the plasminogen N-terminal activation peptide while the tetrapeptide YLLK corresponds the 119-122 segment of the fibrinogen B beta-chain. Spectral comparison of ligand-free and ligand-containing kringle 2 samples leads to the conclusion that all the small ligands as well as the peptides' C-terminal lysyl residues interact with a common binding site in kringle 2. Two-dimensional spectra show that besides the Tyr36, Trp62, His64, Trp72, and Tyr74 aromatic rings, the Val35 and Asp55 aliphatic side chains also participate in ligand binding. Contact points with the ligands 6AHA and BASA were unambiguously identified from kringle 2-ligand nuclear Overhauser effects (NOEs). Overall, the ligand-induced chemical shifts and the intermolecular NOEs correlate remarkably well. Association constant (Ka) values for the kringle 2-ligand interactions were determined. Among the investigated ligands, BASA perturbs the kringle 2 spectrum the most and exhibits the highest affinity for kringle 2 (Ka approximately 233 mM-1). Of the two other aromatic ligands, PAEBA binds to kringle 2 less firmly (Ka = approximately 12 mM-1) than does the one-methylene group shorter analog PAMBA (Ka approximately 31 mM-1). By comparison, relative to 6AHA (Ka approximately 22 mM-1), the longer chain linear aliphatic ligand 7AHA interacts with kringle 2 with significantly higher affinity (Ka approximately 149 mM-1). By reference to the NMR-derived binding site structure, it is suggested that the higher affinity toward 7AHA may stem from (a) a relatively more favored ionic pairing between its carboxylate group and the LYs34 + Arg 69 side-chain cationic centers and (b) an enhanced interaction between the ligand hydrocarbon moiety and the kringle hydrophobic pocket, in particular with the Leu70 side chain. The latter is consistent with the relatively good affinity of kringle 2 for the cyclic hydrocarbon ligand AMCHA (Ka approximately 69 mM-1).(ABSTRACT TRUNCATED AT 400 WORDS)

The two polypeptide chains in fibronectin are joined in antiparallel fashion: NMR structural characterization

The fibronectin C-terminal interchain disulfide-linked heptapeptide dimer (Val-Asn-Cys-Pro-Ile-Glu-Cys)2 has been investigated via 1H NMR spectroscopy in both water and dimethyl sulfoxide (DMSO) solutions. Proton Overhauser experiments in DMSO indicate unambiguously that the two fibronectin polypeptide chains are linked head-to-tail (N-terminus to C-terminus), in an antiparallel fashion. It is found that the structure of the peptide is extended. From the 1H NMR interproton distance and angle constraints, the preferred mean (time-averaged) conformations in both H2O and DMSO were derived using distance geometry and molecular mechanics algorithms. The two conformations, although significantly dissimilar, exhibit the common feature of a structurally parallel (as opposed to chemically antiparallel) fibronectin alpha/beta chain array.