Characterization of a spinach psbS cDNA encoding the 22 kDa protein of photosystem II.

An intrinsic 22 kDa polypeptide is found associated with the oxygen-evolving photosystem II (PSII) core complex in all green plants and cyanobacteria so far examined, although it does not appear to be required for oxygen evolution. Amino acid sequence information obtained from the purified 22 kDa protein was used to construct a probe that was employed to isolate a full-length cDNA clone encoding the 274-residue precursor of the 22 kDa protein. Hydropathy plot analysis predicts the existence of four membrane-spanning helices in the mature protein. The two halves of the approximately 200-residue mature protein show high sequence similarity to each other, suggesting that the psbS gene arose from an internal gene duplication. The 22 kDa protein has some sequence similarity to chlorophyll a/b-binding proteins.     

Visual Cues Given by Humans Are Not Sufficient for Asian Elephants (Elephas maximus) to Find Hidden Food

Recent research suggests that domesticated species – due to artificial selection by humans for specific, preferred behavioral traits – are better than wild animals at responding to visual cues given by humans about the location of hidden food. \Although this seems to be supported by studies on a range of domesticated (including dogs, goats and horses) and wild (including wolves and chimpanzees) animals, there is also evidence that exposure to humans positively influences the ability of both wild and domesticated animals to follow these same cues. Here, we test the performance of Asian elephants (Elephas maximus) on an object choice task that provides them with visual-only cues given by humans about the location of hidden food. Captive elephants are interesting candidates for investigating how both domestication and human exposure may impact cue-following as they represent a non-domesticated species with almost constant human interaction. As a group, the elephants (n = 7) in our study were unable to follow pointing, body orientation or a combination of both as honest signals of food location. They were, however, able to follow vocal commands with which they were already familiar in a novel context, suggesting the elephants are able to follow cues if they are sufficiently salient. Although the elephants’ inability to follow the visual cues provides partial support for the domestication hypothesis, an alternative explanation is that elephants may rely more heavily on other sensory modalities, specifically olfaction and audition. Further research will be needed to rule out this alternative explanation.     

Integrin alpha9beta1 directly binds to vascular endothelial growth factor (VEGF)-A and contributes to VEGF-A-induced angiogenesis

Vascular endothelial growth factor A (VEGF-A) is a potent inducer of angiogenesis. We now show that VEGF-A-induced adhesion and migration of human endothelial cells are dependent on the integrin alpha9beta1 and that VEGF-A is a direct ligand for this integrin. Adhesion and migration of these cells on the 165 and 121 isoforms of VEGF-A depend on cooperative input from alpha9beta1 and the cognate receptor for VEGF-A, VEGF receptor 2 (VEGF-R2). Unlike alpha3beta1or alphavbeta3 integrins, alpha9beta1 was also found to bind the 121 isoform of VEGF-A. This interaction appears to be biologically significant, because alpha9beta1-blocking antibody dramatically and specifically inhibited angiogenesis induced by VEGF-A165 or -121. Together with our previous findings that alpha9beta1 directly binds to VEGF-C and -D and contributes to lymphangiogenesis, these results identify the integrin alpha9beta1 as a potential pharmacotherapeutic target for inhibition of pathogenic angiogenesis and lymphangiogenesis.     

Glycoprotein 120 binding to CXCR4 causes p38-dependent primary T cell death that is facilitated by, but does not require cell-associated CD4

HIV-1 infection causes the depletion of host CD4 T cells through direct and indirect (bystander) mechanisms. Although HIV Env has been implicated in apoptosis of uninfected CD4 T cells via gp120 binding to either CD4 and/or the chemokine receptor 4 (CXCR4), conflicting data exist concerning the molecular mechanisms involved. Using primary human CD4 T cells, we demonstrate that gp120 binding to CD4 T cells activates proapoptotic p38, but does not activate antiapoptotic Akt. Because ligation of the CD4 receptor alone or the CXCR4 receptor alone causes p38 activation and apoptosis, we used the soluble inhibitors, soluble CD4 (sCD4) or AMD3100, to delineate the role of CD4 and CXCR4 receptors, respectively, in gp120-induced p38 activation and death. sCD4 alone augments gp120-induced death, suggesting that CXCR4 signaling is principally responsible. Supporting that model, AMD3100 reduces death caused by gp120 or by gp120/sCD4. Finally, prevention of gp120-CXCR4 interaction with 12G5 Abs blocks p38 activation and apoptosis, whereas inhibition of CD4-gp120 interaction with Leu-3a has no effect. Consequently, we conclude that gp120 interaction with CXCR4 is required for gp120 apoptotic effects in primary human T cells.     

Renal safety of a tenofovir-containing first line regimen: experience from an antiretroviral cohort in rural Lesotho

Introduction

Current guidelines contraindicate TDF use when creatinine clearance (CrCl) falls below 50 ml/min. We report prevalence of abnormal renal function at baseline and factors associated with abnormal renal function from a community cohort in Lesotho.

Methods

We calculated changes in CrCl from baseline for patients initiated on TDF at 6 and 12 months and the proportion of patients initiated on TDF who developed renal impairment. Screening algorithms were developed using risk factors determined by multivariate analysis.

Results

Among 933 adults for whom baseline creatinine was available, 176 (18.9%) presented with a baseline CrCl <50 ml/min. Renal function improved during follow-up. 19 patients who developed renal toxicity during follow up remained on TDF; renal function improved (CrCl≥50 ml/min) in all but 3 of these patients. Among 15 patients with a baseline CrCl <50 ml/min were started in error, none developed severe renal impairment.

Conclusion

In this setting TDF-associated renal toxicity is rare and mainly transient. Further studies to assess TDF safety at lower CrCl thresholds are warranted.     

Cellular Responses to Mechanical Stress: Invited Review: Plasma membrane stress failure in alveolar epithelial cells

Inthis review, we examine the hypothesis that plasma membrane stressfailure is a central event in the pathophysiology of injury fromalveolar overdistension. This hypothesis leads us to consider alveolarmicromechanics and specifically the mechanical interactions betweenlung matrix and alveolar epithelial cell cytoskeleton and plasmamembrane. We then explore events that are central to the regulation ofplasma membrane tension and detail the lipid-trafficking responses ofin vitro deformed and/or injured cells. We conclude with a reference toupregulation of stress-responsive genes after membrane injury and resealing.

     

Invited review: plasma membrane stress failure in alveolar epithelial cells.

In this review, we examine the hypothesis that plasma membrane stress failure is a central event in the pathophysiology of injury from alveolar overdistension. This hypothesis leads us to consider alveolar micromechanics and specifically the mechanical interactions between lung matrix and alveolar epithelial cell cytoskeleton and plasma membrane. We then explore events that are central to the regulation of plasma membrane tension and detail the lipid-trafficking responses of in vitro deformed and/or injured cells. We conclude with a reference to upregulation of stress-responsive genes after membrane injury and resealing.     

UDP-Gal: GlcNAc-R β1,4-galactosyltransferase—a target enzyme for drug design. Acceptor specificity and inhibition of the enzyme

Galactosyltransferases are important enzymes for the extension of the glycan chains of glycoproteins and glycolipids, and play critical roles in cell surface functions and in the immune system. In this work, the acceptor specificity and several inhibitors of bovine β1,4-Gal-transferase T1 (β4GalT, EC 2.4.1.90) were studied. Series of analogs of N-acetylglucosamine (GlcNAc) and GlcNAc-carrying glycopeptides were synthesized as acceptor substrates. Modifications were made at the 3-, 4- and 6-positions of the sugar ring of the acceptor, in the nature of the glycosidic linkage, in the aglycone moiety and in the 2-acetamido group. The acceptor specificity studies showed that the 4-hydroxyl group of the sugar ring was essential for β4GalT activity, but that the 3-hydroxyl could be replaced by an electronegative group. Compounds having the anomeric β-configuration were more active than those having the α-configuration, and O-, S- and C-glycosyl compounds were all active as substrates. The aglycone was a major determinant for the rate of Gal-transfer. Derivatives containing a 2-naphthyl aglycone were inactive as substrates although quinolinyl groups supported activity. Several compounds having a bicyclic structure as the aglycone were found to bind to the enzyme and inhibited the transfer of Gal to control substrates. The best small hydrophobic GlcNAc-analog inhibitor was found to be 1-thio-N-butyrylGlcNβ-(2-naphthyl) with a K_i of 0.01 mM. These studies help to delineate β4GalT–substrate interactions and will aid in the development of biologically applicable inhibitors of the enzyme.     

Anti-Plasmodium activity of imidazole-dioxolane compounds

A series of imidazole-dioxolane compounds, which we hypothesize should bind to heme and thus interfere with heme catabolism in the parasite, were assayed for inhibitory activity in Plasmodium falciparum cultures and the results were compared to those obtained with Chinese hamster ovary (CHO) cells. The majority of the compounds displayed a similar ratio of inhibitory activity in the two culture systems; however, a number of the compounds tested showed promising anti-Plasmodium activity. The mechanism of action of these compounds remains unclear, however their inability to act synergistically with chloroquine suggests that, if they are inhibiting heme detoxification, they do so in a manner that does not complement the action of chloroquine.     

Synthesis and evaluation of imidazole–dioxolane compounds as selective heme oxygenase inhibitors: Effect of substituents at the 4-position of the dioxolane ring

Several imidazole–dioxolane compounds were synthesized and evaluated as novel inhibitors of heme oxygenase (HO). These compounds, which include a series of substituted thiophenol and substituted phenol derivatives of (2R,4S)-2-[2-(4-chlorophenyl)ethyl]-2-[(1H-imidazol-1-yl)methyl]-4-[(phenylsulfanyl)methyl]-1,3-dioxolane hydrochloride (3), in addition to smaller functionalized derivatives, continue our structure–activity studies by exploration of the aminothiophenol region (‘northeastern region’) in our original target structure azalanstat (1). In vitro, most of the compounds in this series were found to be highly potent inhibitors of the stress-induced isozyme HO-1 and the constitutive isozyme HO-2, showing only moderate selectivity for HO-1. Nevertheless, a few of the compounds displayed higher selectivity toward HO-1. None of the compounds having a larger appendage in the northeastern region were inhibitors of CYP2E1, whereas a compound having a relatively small fluorine substituent in this region did inhibit CYP2E1; all of the compounds tested exhibited high inhibitory potency against CYP3A1/3A2.