Insights on the evolution of prolyl 3-hydroxylation sites from comparative analysis of chicken and Xenopus fibrillar collagens

Recessive mutations that prevent 3-hydroxyproline formation in type I collagen have been shown to cause forms of osteogenesis imperfecta. In mammals, all A-clade collagen chains with a GPP sequence at the A1 site (P986), except α1(III), have 3Hyp at residue P986. Available avian, amphibian and reptilian type III collagen sequences from the genomic database (Ensembl) all differ in sequence motif from mammals at the A1 site. This suggests a potential evolutionary distinction in prolyl 3-hydroxylation between mammals and earlier vertebrates. Using peptide mass spectrometry, we confirmed that this 3Hyp site is fully occupied in α1(III) from an amphibian, Xenopus laevis, as it is in chicken. A thorough characterization of all predicted 3Hyp sites in collagen types I, II, III and V from chicken and xenopus revealed further differences in the pattern of occupancy of the A3 site (P707). In mammals only α2(I) and α2(V) chains had any 3Hyp at the A3 site, whereas in chicken all α-chains except α1(III) had A3 at least partially 3-hydroxylated. The A3 site was also partially 3-hydroxylated in xenopus α1(I). Minor differences in covalent cross-linking between chicken, xenopus and mammal type I and III collagens were also found as a potential index of evolving functional differences. The function of 3Hyp is still unknown but observed differences in site occupancy during vertebrate evolution are likely to give important clues.     

Attitudinal and demographic predictors of measles-mumps-rubella vaccine (MMR) uptake during the UK catch-up campaign 2008-09: cross-sectional survey

Background and Objective

Continued suboptimal measles-mumps-rubella (MMR) vaccine uptake has re-established measles epidemic risk, prompting a UK catch-up campaign in 2008–09 for children who missed MMR doses at scheduled age. Predictors of vaccine uptake during catch-ups are poorly understood, however evidence from routine schedule uptake suggests demographics and attitudes may be central. This work explored this hypothesis using a robust evidence-based measure.

Design

Cross-sectional self-administered questionnaire with objective behavioural outcome.

Setting and Participants

365 UK parents, whose children were aged 5–18 years and had received <2 MMR doses before the 2008–09 UK catch-up started.

Main Outcome Measures

Parents'' attitudes and demographics, parent-reported receipt of invitation to receive catch-up MMR dose(s), and catch-up MMR uptake according to child''s medical record (receipt of MMR doses during year 1 of the catch-up).

Results

Perceived social desirability/benefit of MMR uptake (OR = 1.76, 95% CI = 1.09–2.87) and younger child age (OR = 0.78, 95% CI = 0.68–0.89) were the only independent predictors of catch-up MMR uptake in the sample overall. Uptake predictors differed by whether the child had received 0 MMR doses or 1 MMR dose before the catch-up. Receipt of catch-up invitation predicted uptake only in the 0 dose group (OR = 3.45, 95% CI = 1.18–10.05), whilst perceived social desirability/benefit of MMR uptake predicted uptake only in the 1 dose group (OR = 9.61, 95% CI = 2.57–35.97). Attitudes and demographics explained only 28% of MMR uptake in the 0 dose group compared with 61% in the 1 dose group.

Conclusions

Catch-up MMR invitations may effectively move children from 0 to 1 MMR doses (unimmunised to partially immunised), whilst attitudinal interventions highlighting social benefits of MMR may effectively move children from 1 to 2 MMR doses (partially to fully immunised). Older children may be best targeted through school-based programmes. A formal evaluation element should be incorporated into future catch-up campaigns to inform their continuing improvement.     

Optimal infection strategies: should macroparasites hedge their bets?

Despite considerable research into the mechanisms that lead to the persistence of parasites, the huge diversity of macroparasite transmission strategies observed both within and among species has yet to be explained. This may be because questions of parasite persistence are typically addressed at the population level, even though observed transmission rates are determined by infection events at the level of the individual parasite. To help overcome this disparity, a simple model is developed to explore the optimal infection strategy for a macroparasite under a range of selection pressures. The model calculates the fitness of the parasite by considering explicitly the probability of the individual infective stages surviving and infecting. The optimal strategy is highly sensitive to the rate of host availability and, considering the parasite's fitness, it is often preferable to have sub-maximal infectivity to maximise survival during periods of host absence. An important finding is that when parasites are faced with unpredictable conditions such as the time of host availability, the optimum strategy may be to produce offspring that differ in their infection strategies. By spreading the risk in this way, known as bet hedging, parasites can increase the chances that at least some of their offspring will infect successfully. This potential for variation in infection strategies has not been considered explicitly before and may have wide reaching implications for current epidemiology theory.     

Altered glycan structures: the molecular basis of congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are a group of diseases that affect glycoprotein biogenesis. Eighteen different types of CDG have been defined genetically. They result from deficiencies in either the biosynthesis of oligosaccharide precursors or specific steps of N-glycan assembly, resulting in the absence or structural alteration of N-glycan chains. These diseases have a broad range of clinical phenotypes and affect nearly every organ system, with special emphasis on normal brain development and the multiple functions of the nervous, hepatic, gastrointestinal and immune systems. Although most of the deficiencies observed in CDG patients are only partial, the severity of the clinical manifestations signifies the relevance of protein N-glycosylation and shows the importance of defined glycan structures.     

Prostate epithelial stem cells

The prostate gland is the site of the most commonly diagnosed cancer in men in USA and UK, accounting for one in five of new cases of male cancer. Common with many other cancer types, prostate cancer is believed to arise from a stem cell that shares characteristics with the normal stem cell. Normal prostate epithelial stem cells were recently identified and found to have a basal cell phenotype together with expression of CD133. Preliminary data have now emerged for a prostate cancer stem cell that also expresses cell surface CD133 but lacks expression of the androgen receptor. Here we examine the evidence supporting the existence of prostate cancer stem cells and discuss possible mechanisms of stem cell maintenance.     

Modulators of the human CCR5 receptor. Part 1: Discovery and initial SAR of 1-(3,3-diphenylpropyl)-piperidinyl amides and ureas

Investigation of weak screening hits led to the identification of N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenylacetamides and N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-N'-benzylureas as potent, selective ligands for the human CCR5 chemokine receptor.     

Chemical Shifts Provide Fold Populations and Register of β Hairpins and β Sheets

A detailed analysis of peptide backbone amide (H_N) and Hα chemical shifts reveals a consistent pattern for β hairpins and three-stranded β sheets. The Hα’s at non-hydrogen-bonded strand positions are inwardly directed and shifted downfield ~1 ppm due largely to an anisotropy contribution from the cross-strand amide function. The secondary structure associated Hα shift deviations for the H-bonded strand positions are also positive but much smaller (0.1–0.3 ppm) and the turn residues display negative Hα chemical shift deviations (CSDs). The pattern of (H_N) shift deviations is an even better indicator of both hairpin formation and register, with the cross-strand H-bonded sites shifted downfield (also by ~1 ppm) and with diagnostic values for the first turn residue and the first strand position following the turn. These empirical observations, initially made for [2:2]/[2:4]-type-I' and -II' hairpins, are rationalized and can be extended to the analysis of other turns, hairpin classes ([3:5], [4:4]/[4:6]), and three-stranded peptide β-sheet models. The Hα’s at non-hydrogen-bonded sites and (H_N)’s in the intervening H-bonded sites provide the largest and most dependable measures of hairpin structuring and can be used for melting studies; however the intrinsic temperature dependence of (H_N) shifts deviations needs to reflect the extent of solvent sequestration in the folded state. Several observations made in the course of this study provide insights into β-sheet folding mechanisms: (1) The magnitude of the (H_N) shifts suggests that the cross-strand H-bonds in peptide hairpins are as short as those in protein β sheets. (2) Even L-Pro-Gly turns, which are frequently used in unfolded controls for hairpin peptides, can support hairpin populations in aqueous fluoroalcohol media. (3) The good correlation between hairpin population estimates from cross-strand H-bonded (H_N) shift deviations, Hα shift deviations, and structuring shifts at the turn locus implies that hairpin folding transitions approximate two-state behavior. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Interactions between intrinsic and extrinsic mechanisms in a cyclic species: testosterone increases parasite infection in red grouse

Field studies of mechanisms involved in population regulation have tended to focus on the roles of either intrinsic or extrinsic factors, but these are rarely mutually exclusive and their interactions can be crucial in determining dynamics. Experiments on red grouse Lagopus lagopus scoticus have shown that population instability can be caused both by the effects of a parasitic nematode, Trichostrongylus tenuis, on host production or by changes in testosterone influencing aggressive behaviour and recruitment. We experimentally tested for an interaction between testosterone and T. tenuis in free-living male grouse. A total of 123 grouse were caught in autumn, treated with an anthelmintic to remove parasites, and then given either testosterone or empty, control, implants. After one month grouse were re-infected with a standard dose of parasites. We show that males with increased testosterone levels had greater parasite intensities than controls after one year. We discuss possible physiological and behavioural mechanisms linking testosterone and increased parasite intensity, and the implications for our understanding of complex, unstable population dynamics.     

Distinct mechanisms of integrin binding by Yersinia pseudotuberculosis adhesins determine the phagocytic response of host macrophages

The enteropathogenic yersiniae express two outer membrane adhesins, invasin and YadA, that contribute to pathogenesis. While invasin binds directly to beta1 integrin receptors with high affinity, YadA binds indirectly through extracellular matrix (ECM) components. In this study, Yersinia pseudotuberculosis inv and yadA mutants were used to investigate how these distinct binding mechanisms compare and potentially compete in activating signalling pathways and promoting bacterial uptake by host macrophages. The efficiency of adhesin-mediated phagocytic responses was found to be dependent on the relative expression of invasin and YadA on the bacterial surface as well as the expression of ECM proteins in the extracellular milieu. Under conditions of low concentrations of ECM, invasin was found to be the dominant adhesin, promoting high levels of phagocytosis coincident with robust and sustained activation of the protein tyrosine kinases Fak and Pyk2, phosphorylation of the adaptor molecule Cas and activation of the small GTPase Rac1. In the presence of higher concentrations of ECM, YadA became the dominant functional adhesin through its ability to engage integrin receptors via an ECM bridge. We propose a model whereby invasin promotes robust and prolonged activation of phagocytic signalling cascades by inducing a 'high-affinity' integrin conformation as well as integrin clustering. We postulate that YadA-ECM promotes phagocytosis through a more transient activation of signalling cascades that arises from integrin clustering in the context of a cross-linked fibrillar ECM network.