Crystal structure of the cold-active aminopeptidase from Colwellia psychrerythraea, a close structural homologue of the human bifunctional leukotriene A4 hydrolase

peer reviewedThe crystal structure of a cold-active aminopeptidase (ColAP) from Colwellia psychrerythraea strain 34H has been determined, extending the number of crystal structures of the M1 metallopeptidase family to four among the 436 members currently identified. In agreement with their sequence similarity, the overall structure of ColAP displayed a high correspondence with leukotriene A4 hydrolase (LTA4H), a human bifunctional enzyme that converts leukotriene A4 (LTA4) in the potent chemoattractant leukotriene B4. Indeed, both enzymes are composed of three domains, an N-terminal saddle-like domain, a catalytic thermolysin-like domain, and a less conserved C-terminal alpha-helical flat spiral domain. Together, these domains form a deep cavity harboring the zinc binding site formed by residues included in the conserved HEXXHX(18)H motif. A detailed structural comparison of these enzymes revealed several plausible determinants of ColAP cold adaptation. The main differences involve specific amino acid substitutions, loop content and solvent exposure, complexity and distribution of ion pairs, and differential domain flexibilities. Such elements may act synergistically to allow conformational flexibility needed for an efficient catalysis in cold environments. Furthermore, the region of ColAP corresponding to the aminopeptidase active site of LTA4H is much more conserved than the suggested LTA4 substrate binding region. This observation supports the hypothesis that this region of the LTA4H active site has evolved in order to fit the lipidic substrate

Cold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations of an aminopeptidase from the Arctic psychrophile Colwellia psychrerythraea and of human leukotriene A(4) hydrolase

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or local structural flexibility, which results in low stability. Analysis of the thermodynamic parameters of irreversible thermal unfolding suggests that entropy-driven factors are responsible for the fast unfolding rate of the cold-adapted aminopeptidase. A reduced number of proline residues, a lower degree of hydrophobic residue burial and a decreased surface accessibility of charged residues may be responsible for this effect. On the other hand, the reduction in enthalpy-driven interactions is the primary determinant of the weak conformational stability

Epithelial Immunomodulation by Aerosolized Toll like Receptor Agonists Attenuate Allergic Responsiveness in Mice

https://openworks.mdanderson.org/sumexp21/1031/thumbnail.jp

Cytokine Profiles of Severe Influenza Virus-Related Complications in Children

RationaleEffective immunomodulatory therapies for children with life-threatening “cytokine storm” triggered by acute influenza infection are lacking. Understanding the immune profiles of children progressing to severe lung injury and/or septic shock could provide insight into pathogenesis.ObjectivesTo compare the endotracheal and serum cytokine profiles of children with influenza-related critical illness and to identify their associations with severe influenza-associated complications.MethodsChildren with influenza-related critical illness were enrolled across 32 hospitals in development (N = 171) and validation (N = 73) cohorts (December 2008 through May 2016). Concentrations of 42 cytokines were measured in serum and endotracheal samples and clustered into modules of covarying cytokines. Relative concentrations of cytokines and cytokine modules were tested for associations with acute lung injury (ALI), shock requiring vasopressors, and death/ECMO.Measurements and main resultsModules of covarying cytokines were more significantly associated with disease severity than individual cytokines. In the development cohort, increased levels of a serum module containing IL6, IL8, IL10, IP10, GCSF, MCP1, and MIP1α [shock odds ratio (OR) = 3.37, family-wise error rate (FWER) p < 10−4], and decreased levels of a module containing EGF, FGF2, SCD40L, and PAI-1 (shock OR = 0.43, FWER p = 0.002), were both associated with ALI, shock, and death-ECMO independent of age and bacterial coinfection. Both of these associations were confirmed in the validation cohort. Endotracheal and serum cytokine associations differed markedly and were differentially associated with clinical outcomes.ConclusionWe identified strong positive and negative associations of cytokine modules with the most severe influenza-related complications in children, providing new insights into the pathogenesis of influenza-related critical illness in children. Effective therapies may need to target mediators of both inflammation and repair

Chromosome Xq23 is associated with lower atherogenic lipid concentrations and favorable cardiometabolic indices

Abstract Autosomal genetic analyses of blood lipids have yielded key insights for coronary heart disease (CHD). However, X chromosome genetic variation is understudied for blood lipids in large sample sizes. We now analyze genetic and blood lipid data in a high-coverage whole X chromosome sequencing study of 65,322 multi-ancestry participants and perform replication among 456,893 European participants. Common alleles on chromosome Xq23 are strongly associated with reduced total cholesterol, LDL cholesterol, and triglycerides (min P = 8.5 × 10−72), with similar effects for males and females. Chromosome Xq23 lipid-lowering alleles are associated with reduced odds for CHD among 42,545 cases and 591,247 controls (P = 1.7 × 10−4), and reduced odds for diabetes mellitus type 2 among 54,095 cases and 573,885 controls (P = 1.4 × 10−5). Although we observe an association with increased BMI, waist-to-hip ratio adjusted for BMI is reduced, bioimpedance analyses indicate increased gluteofemoral fat, and abdominal MRI analyses indicate reduced visceral adiposity. Co-localization analyses strongly correlate increased CHRDL1 gene expression, particularly in adipose tissue, with reduced concentrations of blood lipids