Invasive and adherent bacterial pathogens co-Opt host clathrin for infection

Infection by the bacterium Listeria monocytogenes depends on host cell clathrin. To determine whether this requirement is widespread, we analyzed infection models using diverse bacteria. We demonstrated that bacteria that enter cells following binding to cellular receptors (termed "zippering" bacteria) invade in a clathrin-dependent manner. In contrast, bacteria that inject effector proteins into host cells in order to gain entry (termed "triggering" bacteria) invade in a clathrin-independent manner. Strikingly, enteropathogenic Escherichia coli (EPEC) required clathrin to form actin-rich pedestals in host cells beneath adhering bacteria, even though this pathogen remains extracellular. Furthermore, clathrin accumulation preceded the actin rearrangements necessary for Listeria entry. These data provide evidence for a clathrin-based entry pathway allowing internalization of large objects (bacteria and ligand-coated beads) and used by "zippering" bacteria as part of a general mechanism to invade host mammalian cells. We also revealed a nonendocytic role for clathrin required for extracellular EPEC infections.     

Emancipating ethics: an autonomist reading of Islamic forms of life in Russia

This article advances a framework aimed at capturing the political life of ethical intensity by putting autonomist theory in resonance with ethnographic material pertaining to quietist Muslim milieus in post-Soviet Russia. The emancipatory and prefigurative potential of collective projects of self-legislation – in this case, ‘halal living’ – are explored through the notions of ethical form of life and Rule/Law. It will be argued that autonomist theory (a) is helpful in conceptualizing the friction between ethical projects (however quietist) and dominant moral/political orders; (b) has the potential to broaden anthropological conversations on virtue beyond existing fault lines (notably between what I call ‘traditionist’ and ‘liberal’ theoretical families) as well as conceptual silos (‘religion', ‘secularity’); and (c) can help us envision a radical, politically engaged anthropology of ethics.     

Structure of an engineered intein reveals thiazoline ring and provides mechanistic insight

We have engineered an intein which spontaneously and reversibly forms a thiazoline ring at the native N-terminal Lys-Cys splice junction. We identified conditions to stablize the thiazoline ring and provided the first crystallographic evidence, at 1.54 Å resolution, for its existence at an intein active site. The finding bolsters evidence for a tetrahedral oxythiazolidine splicing intermediate. In addition, the pivotal mutation maps to a highly conserved B-block threonine, which is now seen to play a causative role not only in ground-state destabilization of the scissile N-terminal peptide bond, but also in steering the tetrahedral intermediate toward thioester formation, giving new insight into the splicing mechanism. We demonstrated the stability of the thiazoline ring at neutral pH as well as sensitivity to hydrolytic ring opening under acidic conditions. A pH cycling strategy to control N-terminal cleavage is proposed, which may be of interest for biotechnological applications requiring a splicing activity switch, such as for protein recovery in bioprocessing.     

Opposite fates of the purine metabolite allantoin under water and nitrogen limitations in bread wheat

Plant Molecular Biology - Degradation of nitrogen-rich purines is tightly and oppositely regulated under drought and low nitrogen supply in bread wheat. Allantoin is a key target metabolite for...     

Construction and structure studies of DNA-bipyridine complexes as versatile scaffolds for site-specific incorporation of metal ions into DNA

The facile construction of metal–DNA complexes using ‘Click’ reactions is reported here. A series of 2′-propargyl-modified DNA oligonucleotides were initially synthesized as structure scaffolds and were then modified through ‘Click’ reaction to incorporate a bipyridine ligand equipped with an azido group. These metal chelating ligands can be placed in the DNA context in site-specific fashion to provide versatile templates for binding various metal ions, which are exchangeable using a simple EDTA washing-and-filtration step. The constructed metal–DNA complexes were found to be thermally stable. Their structures were explored by solving a crystal structure of a propargyl-modified DNA duplex and installing the bipyridine ligands by molecular modeling and simulation. These metal–DNA complexes could have wide applications as novel organometallic catalysts, artificial ribonucleases, and potential metal delivery systems.     

Tick tock,tick tock: Mouse culture and tissue aging captured by an epigenetic clock

Aging is associated with dramatic changes to DNA methylation (DNAm), although the causes and consequences of such alterations are unknown. Our ability to experimentally uncover mechanisms of epigenetic aging will be greatly enhanced by our ability to study and manipulate these changes using in vitro models. However, it remains unclear whether the changes elicited by cells in culture can serve as a model of what is observed in aging tissues in vivo. To test this, we serially passaged mouse embryonic fibroblasts (MEFs) and assessed changes in DNAm at each time point via reduced representation bisulfite sequencing. By developing a measure that tracked cellular aging in vitro, we tested whether it tracked physiological aging in various mouse tissues and whether anti‐aging interventions modulate this measure. Our measure, termed CultureAGE, was shown to strongly increase with age when examined in multiple tissues (liver, lung, kidney, blood, and adipose). As a control, we confirmed that the measure was not a marker of cellular senescence, suggesting that it reflects a distinct yet progressive cellular aging phenomena that can be induced in vitro. Furthermore, we demonstrated slower epigenetic aging in animals undergoing caloric restriction and a resetting of our measure in lung and kidney fibroblasts when re‐programmed to iPSCs. Enrichment and clustering analysis implicated EED and Polycomb group (PcG) factors as potentially important chromatin regulators in translational culture aging phenotypes. Overall, this study supports the concept that physiologically relevant aging changes can be induced in vitro and used to uncover mechanistic insights into epigenetic aging.     

Malaria in migrants

An increasing proportion of malaria cases in Italy is observed in immigrants revisiting their country of origin, but little specific research work has been carried out in this field. All malaria cases occurring from 1990 to 1998 at the Reference Clinic for Infectious and Tropical Diseases in Brescia were prospectically evaluated to compare clinical outcome in migrant and non-immune cases. No difference was observed between parasitaemia at diagnosis and time to clearance of peripheral parasitaemia. Clinical presentation was milder in migrants than in non-immunes, with an OR for severe malaria of 0.27 (c.i. = 0.09-0.84) (p = 0.01). Fever clearance time was significantly shorter in migrants (3.0 days, SD = 1.2) than in non-immunes (4.3 days, SD = 1.7) (p < 0.001). Among immigrants, the proportion of severe cases was higher in residents since 2 years or less (12.5%) compared to residents since 2 to 5 years (3.3%) and residents since more than 5 years (0.9%) (p = 0.02). The proportion of malaria cases who had used chemoprophylaxis was significantly lower among immigrants (30/272, 11.0%) compared to non-immunes (41/74, 55.4%) (p < 0.001). In a population based malaria KAP analysis among 504 migrants from malaria endemic countries, correct knowledge of malaria risk was reported by 351 (69.5%). Of 170 subjects who reported at least one visit back to the home country, 30 (17.6%) had sought pre-travel advice, 24 (14.1%) had started chemoprophylaxis and 7 (4.1%) had completed it during the last visit. Of 140 migrants who failed to seek pre-travel advice, 73 (52%) were unaware of malaria risk, 56 (40%) did not know how to protect themselves, and 11 (8%) refused to use protective measures. Migrants account for a significant proportion of imported malaria cases in industrialised countries. Clinical presentation is milder compared to non-immune subjects. The proportion of migrants who adopt malaria protective measure while returning home is very low, due to both unawareness of risk and inappropriateness of medical advice.