bluuebunny/crossref_metadata_2025_split huggingface dataset:
The
N
-Acetylmuramic Acid 6-Phosphate Phosphatase MupP Completes the
Pseudomonas
Peptidoglycan Recycling Pathway Leading to Intrinsic Fosfomycin Resistance
Authors: Borisova Marina , Gisin Jonathan , Mayer Christoph 
Published: March 2017

ABSTRACT

Bacterial cells are encased in and stabilized by a netlike peptidoglycan (PGN) cell wall that undergoes turnover during bacterial growth. PGN turnover fragments are frequently salvaged by the cells via a pathway referred to as PGN recycling. Two different routes for the recycling of the cell wall sugar
N
-acetylmuramic acid (MurNAc) have been recognized in bacteria. In
Escherichia coli
and related enterobacteria, as well as in most Gram-positive bacteria, MurNAc is recovered via a catabolic route requiring a MurNAc 6-phosphate etherase (MurQ in
E. coli
) enzyme. However, many Gram-negative bacteria, including
Pseudomonas
species, lack a MurQ ortholog and use an alternative, anabolic recycling route that bypasses the
de novo
biosynthesis of uridyldiphosphate (UDP)-MurNAc, the first committed precursor of PGN. Bacteria featuring the latter pathway become intrinsically resistant to the antibiotic fosfomycin, which targets the
de novo
biosynthesis of UDP-MurNAc. We report here the identification and characterization of a phosphatase enzyme, named MupP, that had been predicted to complete the anabolic recycling pathway of
Pseudomonas
species but has remained unknown so far. It belongs to the large haloacid dehalogenase family of phosphatases and specifically converts MurNAc 6-phosphate to MurNAc. A Δ
mupP
mutant of
Pseudomonas putida
was highly susceptible to fosfomycin, accumulated large amounts of MurNAc 6-phosphate, and showed lower levels of UDP-MurNAc than wild-type cells, altogether consistent with a role for MupP in the anabolic PGN recycling route and as a determinant of intrinsic resistance to fosfomycin.

IMPORTANCE
Many Gram-negative bacteria, but not
E. coli
, make use of a cell wall salvage pathway that contributes to the pool of UDP-MurNAc, the first committed precursor of cell wall synthesis in bacteria. This salvage pathway is of particular interest because it confers intrinsic resistance to the antibiotic fosfomycin, which blocks
de novo
UDP-MurNAc biosynthesis. Here we identified and characterized a previously missing enzyme within the salvage pathway, the MurNAc 6-phosphate phosphatase MupP of
P. putida
. MupP, together with the other enzymes of the anabolic recycling pathway, AnmK, AmgK, and MurU, yields UDP-MurNAc, renders bacteria intrinsically resistant to fosfomycin, and thus may serve as a novel drug target for antimicrobial therapy.
Mouse Mammary Tumor Virus Signal Peptide Uses a Novel p97-Dependent and Derlin-Independent Retrotranslocation Mechanism To Escape Proteasomal Degradation
Authors: Byun Hyewon , Das Poulami , Yu Houqing , Aleman Alejandro , Lozano Mary M. , Matouschek Andreas , Dudley Jaquelin P. 
Published: March 2017

ABSTRACT
Multiple pathogens, including viruses and bacteria, manipulate endoplasmic reticulum-associated degradation (ERAD) to avoid the host immune response and promote their replication. The betaretrovirus mouse mammary tumor virus (MMTV) encodes Rem, which is a precursor protein that is cleaved into a 98-amino-acid signal peptide (SP) and a C-terminal protein (Rem-CT). SP uses retrotranslocation for ER membrane extraction and yet avoids ERAD by an unknown mechanism to enter the nucleus and function as a Rev-like protein. To determine how SP escapes ERAD, we used a ubiquitin-activated interaction trap (UBAIT) screen to trap and identify transient protein interactions with SP, including the ERAD-associated p97 ATPase, but not E3 ligases or Derlin proteins linked to retrotranslocation, polyubiquitylation, and proteasomal degradation of extracted proteins. A dominant negative p97 ATPase inhibited both Rem and SP function. Immunoprecipitation experiments indicated that Rem, but not SP, is polyubiquitylated. Using both yeast and mammalian expression systems, linkage of a ubiquitin-like domain (UbL) to SP or Rem induced degradation by the proteasome, whereas SP was stable in the absence of the UbL. ERAD-associated Derlin proteins were not required for SP activity. Together, these results suggested that Rem uses a novel p97-dependent, Derlin-independent retrotranslocation mechanism distinct from other pathogens to avoid SP ubiquitylation and proteasomal degradation.

IMPORTANCE
Bacterial and viral infections produce pathogen-specific proteins that interfere with host functions, including the immune response. Mouse mammary tumor virus (MMTV) is a model system for studies of human complex retroviruses, such as HIV-1, as well as cancer induction. We have shown that MMTV encodes a regulatory protein, Rem, which is cleaved into an N-terminal signal peptide (SP) and a C-terminal protein (Rem-CT) within the endoplasmic reticulum (ER) membrane. SP function requires ER membrane extraction by retrotranslocation, which is part of a protein quality control system known as ER-associated degradation (ERAD) that is essential to cellular health. Through poorly understood mechanisms, certain pathogen-derived proteins are retrotranslocated but not degraded. We demonstrate here that MMTV SP retrotranslocation from the ER membrane avoids degradation through a unique process involving interaction with cellular p97 ATPase and failure to acquire cellular proteasome-targeting sequences.
Plasmodium falciparum Maf1
Confers Survival upon Amino Acid Starvation
Authors: McLean Kyle Jarrod , Jacobs-Lorena Marcelo 
Published: March 2017

ABSTRACT

The target of rapamycin complex 1 (
TORC1
) pathway is a highly conserved signaling pathway across eukaryotes that integrates nutrient and stress signals to regulate the cellular growth rate and the transition into and maintenance of dormancy. The majority of the pathway’s components, including the central
TOR
kinase, have been lost in the apicomplexan lineage, and it is unknown how these organisms detect and respond to nutrient starvation in its absence.
Plasmodium falciparum
encodes a putative ortholog of the RNA polymerase (Pol) III repressor
Maf1
, which has been demonstrated to modulate Pol III transcription in a TOR-dependent manner in a number of organisms. Here, we investigate the role of
P. falciparum Maf1
(
PfMaf1
) in regulating RNA Pol III expression under conditions of nutrient starvation and other stresses. Using a transposon insertion mutant with an altered
Maf1
expression profile, we demonstrated that proper
Maf1
expression is necessary for survival of the dormancy-like state induced by prolonged amino acid starvation and is needed for full recovery from other stresses that slow or stall the parasite cell cycle. This
Maf1
mutant is defective in the downregulation of pre-tRNA synthesis under nutrient-limiting conditions, indicating that the function of
Maf1
as a stress-responsive regulator of structural RNA transcription is conserved in
P. falciparum
. Recent work has demonstrated that parasites carrying artemisinin-resistant
K13
alleles display an enhanced ability to recover from drug-induced growth retardation. We show that one such artemisinin-resistant line displays greater regulation of pre-tRNA expression and higher survival upon prolonged amino acid starvation, suggesting that overlapping,
Pf
Maf1-associated pathways may regulate growth recovery from both artemisinin treatment and amino acid starvation.

IMPORTANCE
Eukaryote organisms sense changes in their environment and integrate this information through signaling pathways to activate response programs to ensure survival. The
TOR
pathway is a well-studied signaling pathway found throughout eukaryotes that is known to integrate a variety of signals to regulate organismal growth in response to starvation and other stresses. The human malaria parasite
Plasmodium falciparum
appears to have lost the
TOR
pathway over the course of evolution, and it is unclear how the parasite modulates its growth in response to starvation and drug treatment. Here, we show that Maf1, a protein regulated by
TOR
in other eukaryotes, plays an important role in maintaining the parasite’s viability in the face of starvation and other forms of stress. This suggests that
PfMaf1
is a component of a yet-to-be-described nutrient and stress response pathway.
Cause of death and potentially avoidable deaths in Australian adults with intellectual disability using retrospective linked data
Authors: Trollor Julian , Srasuebkul Preeyaporn , Xu Han , Howlett Sophie 
Published: March 2017

ObjectivesTo investigate mortality and its causes in adults over the age of 20 years with intellectual disability (ID).Design, setting and participantsRetrospective population-based standardised mortality of the ID and Comparison cohorts. The ID cohort comprised 42 204 individuals who registered for disability services with ID as a primary or secondary diagnosis from 2005 to 2011 in New South Wales (NSW). The Comparison cohort was obtained from published deaths in NSW from the Australian Bureau of Statistics (ABS) from 2005 to 2011.Main outcome measuresWe measured and compared Age Standardised Mortality Rate (ASMR), Comparative Mortality Figure (CMF), years of productive life lost (YPLL) and proportion of deaths with potentially avoidable causes in an ID cohort with an NSW general population cohort.ResultsThere were 19 362 adults in the ID cohort which experienced 732 (4%) deaths at a median age of 54 years. Age Standardised Mortality Rates increased with age for both cohorts. Overall comparative mortality figure was 1.3, but was substantially higher for the 20–44 (4.0) and 45–64 (2.3) age groups. YPLL was 137/1000 people in the ID cohort and 49 in the comparison cohort. Cause of death in ID cohort was dominated by respiratory, circulatory, neoplasm and nervous system. After recoding deaths previously attributed to the aetiology of the disability, 38% of deaths in the ID cohort and 17% in the comparison cohort were potentially avoidable.ConclusionsAdults with ID experience premature mortality and over-representation of potentially avoidable deaths. A national system of reporting of deaths in adults with ID is required. Inclusion in health policy and services development and in health promotion programmes is urgently required to address premature deaths and health inequalities for adults with ID.
Comparison of the therapeutic dose of warfarin in HIV-infected and HIV-uninfected patients: a study of clinical practice
Authors: Jackson B S , Mokoena T 
Published: March 2017

BackgroundPeople infected with HIV are prone to venous thrombosis. Treatment of thrombosis is primarily with warfarin. No studies have addressed the effects of HIV infection on warfarin dose. The aims of this study were to determine whether the therapeutic dose of warfarin and induction time to therapeutic dose in HIV-infected patients differ from that in HIV-uninfected patients.MethodsA prospective and retrospective descriptive study of induction time to therapeutic warfarin dose, as well as of ambulant therapeutic warfarin dose, was performed. HIV-infected and HIV-uninfected patients being treated after deep venous thrombosis with or without pulmonary embolism were compared. Sex and use of antiretroviral drugs (ARVs) were also compared in the groups.Results234 patients were entered into the study. Induction time to therapeutic warfarin dose did not differ between the 2 groups. The mean therapeutic dose of warfarin was higher in the HIV-infected than the HIV-uninfected group: 6.06 vs 5.72 mg/day, but this was not statistically significant (p=0.29). There was no difference in therapeutic warfarin dose between ARV-naïve groups—HIV-uninfected and HIV-infected patients not on ARVs.ConclusionsThere appears to be little effect of HIV infection on warfarin dosing. Warfarin therapy should be administered conventionally in HIV-infected patients.
Green shoots of recovery: a realist evaluation of a team to support change in general practice
Authors: Bartlett Maggie , Basten Ruth , McKinley Robert K 
Published: March 2017

ObjectiveA multidisciplinary support team for general practice was established in April 2014 by a local National Health Service (NHS) England management team. This work evaluates the team's effectiveness in supporting and promoting change in its first 2 years, using realist methodology.SettingPrimary care in one area of England.ParticipantsSemistructured interviews were conducted with staff from 14 practices, 3 key senior NHS England personnel and 5 members of the support team. Sampling of practice staff was purposive to include representatives from relevant professional groups.InterventionThe team worked with practices to identify areas for change, construct action plans and implement them. While there was no specified timescale for the team's work with practices, it was tailored to each.Primary and secondary outcome measuresIn realist evaluations, outcomes are contingent on mechanisms acting in contexts, and both an understanding of how an intervention leads to change in a socially constructed system and the resultant changes are outcomes.ResultsThe principal positive mechanisms leading to change were the support team's expertise and its relationships with practice staff. The ‘external view’ provided by the team via its corroborative and normalising effects was an important mechanism for increasing morale in some practice contexts. A powerful negative mechanism was related to perceptions of ‘being seen as a failing practice’ which included expressions of ‘shame’. Outcomes for practices as perceived by their staff were better communication, improvements in patients' access to appointments resulting from better clinical and managerial skill mix, and improvements in workload management.ConclusionsThe support team promoted change within practices leading to signs of the ‘green shoots of recovery’ within the time frame of the evaluation. Such interventions need to be tailored and responsive to practices' needs. The team's expertise and relationships between team members and practice staff are central to success.
Development and long-term integration of MGE-lineage cortical interneurons in the heterochronic environment
Authors: Larimer Phillip , Spatazza Julien , Stryker Michael P. , Alvarez-Buylla Arturo , Hasenstaub Andrea R. 
Published: March 2017

Interneuron precursors transplanted into visual cortex induce network plasticity during their heterochronic maturation. Such plasticity can have a significant impact on the function of the animal and is normally present only during a brief critical period in early postnatal development. Elucidating the synaptic and physiological properties of interneuron precursors as they mature is key to understanding how long-term circuit changes are induced by transplants. We studied the development of transplant-derived interneurons and compared it to endogenously developing interneurons (those that are born and develop in the same animal) at parallel developmental time points, using patch-clamp recordings in acute cortical slices. We found that transplant-derived interneurons develop into fast-spiking and non-fast-spiking neurons characteristic of the medial ganglionic eminence (MGE) lineage. Transplant-derived interneurons matured more rapidly than endogenously developing interneurons, as shown by more hyperpolarized membrane potentials, smaller input resistances, and narrower action potentials at a juvenile age. In addition, transplant-derived fast-spiking interneurons have more quickly saturating input-output relationships and lower maximal firing rates in adulthood, indicating a possible divergence in function. Transplant-derived interneurons both form inhibitory synapses onto host excitatory neurons and receive excitatory synapses from host pyramidal cells. Unitary connection properties are similar to those of host interneurons. These transplant-derived interneurons, however, were less densely functionally connected onto host pyramidal cells than were host interneurons and received fewer spontaneous excitatory inputs from host cells. These findings suggest that many physiological characteristics of interneurons are autonomously determined, while some factors impacting their circuit function may be influenced by the environment in which they develop. NEW & NOTEWORTHY Transplanting embryonic interneurons into older brains induces a period of plasticity in the recipient animal. We find that these interneurons develop typical fast-spiking and non-fast-spiking phenotypes by the end of adolescence. However, the input-output characteristics of transplant-derived neurons diverged from endogenously developing interneurons during adulthood, and they showed lower connection rates to local pyramidal cells at all time points. This suggests a unique and ongoing role of transplant-derived interneurons in host circuits, enabling interneuron transplant therapies.
Contributions of space-clamp errors to apparent time-dependent loss of Mg2+ block induced by NMDA
Authors: Sun Min-Yu , Chisari Mariangela , Eisenman Lawrence N. , Zorumski Charles F. , Mennerick Steven J. 
Published: March 2017

N-methyl-d-aspartate receptors (NMDARs) govern synaptic plasticity, development, and neuronal response to insult. Prolonged activation of NMDARs such as during an insult may activate secondary currents or modulate Mg2+ sensitivity, but the conditions under which these occur are not fully defined. We reexamined the effect of prolonged NMDAR activation in juvenile mouse hippocampal slices. NMDA (10 μM) elicited current with the expected negative-slope conductance in the presence of 1.2 mM Mg2+. However, several minutes of continued NMDA exposure elicited additional inward current at −70 mV. A higher concentration of NMDA (100 µM) elicited the current more rapidly. The additional current was not dependent on Ca2+, network activity, or metabotropic NMDAR function and did not persist on agonist removal. Voltage ramps revealed no alteration of either reversal potential or NMDA-elicited conductance between −30 mV and +50 mV. The result was a more linear NMDA current-voltage relationship. The current linearization was also induced in interneurons and in mature dentate granule neurons but not immature dentate granule cells, dissociated cultured hippocampal neurons, or nucleated patches excised from CA1 pyramidal neurons. Comparative simulations of NMDA application to a CA1 pyramidal neuron and to a cultured neuron revealed that linearization can be explained by space-clamp errors arising from gradual recruitment of distal dendritic NMDARs. We conclude that persistent secondary currents do not strongly contribute to NMDAR responses in juvenile mouse hippocampus and careful discernment is needed to exclude contributions of clamp artifacts to apparent secondary currents. NEW & NOTEWORTHY We report that upon sustained activation of NMDARs in juvenile mouse hippocampal neurons there is apparent loss of Mg2+ block at negative membrane potentials. However, the phenomenon is explained by loss of dendritic voltage clamp, leading to a linear current-voltage relationship. Our results give a specific example of how spatial voltage errors in voltage-clamp recordings can readily be misinterpreted as biological modulation.
Functional remodeling of subtype-specific markers surrounding implanted neuroprostheses
Authors: Salatino Joseph W. , Winter Bailey M. , Drazin Matthew H. , Purcell Erin K. 
Published: March 2017

Microelectrode arrays implanted in the brain are increasingly used for the research and treatment of intractable neurological disease. However, local neuronal loss and glial encapsulation are known to interfere with effective integration and communication between implanted devices and brain tissue, where these observations are typically based on assessments of broad neuronal and astroglial markers. However, both neurons and astrocytes comprise heterogeneous cellular populations that can be further divided into subclasses based on unique functional and morphological characteristics. In this study, we investigated whether or not device insertion causes alterations in specific subtypes of these cells. We assessed the expression of both excitatory and inhibitory markers of neurotransmission (vesicular glutamate and GABA transporters, VGLUT1 and VGAT, respectively) surrounding single-shank Michigan-style microelectrode arrays implanted in the motor cortex of adult rats by use of quantitative immunohistochemistry. We found a pronounced shift from significantly elevated VGLUT1 within the initial days following implantation to relatively heightened VGAT by the end of the 4-wk observation period. Unexpectedly, we observed VGAT positivity in a subset of reactive astrocytes during the first week of implantation, indicating heterogeneity in early-responding encapsulating glial cells. We coupled our VGLUT1 data with the evaluation of a second marker of excitatory neurons (CamKiiα); the results closely paralleled each other and underscored a progression from initially heightened to subsequently weakened excitatory tone in the neural tissue proximal to the implanted electrode interface (within 40 μm). Our results provide new evidence for subtype-specific remodeling surrounding brain implants that inform observations of suboptimal integration and performance. NEW & NOTEWORTHY We report novel changes in the local expression of excitatory and inhibitory synaptic markers surrounding microelectrode arrays implanted in the motor cortex of rats, where a progressive shift toward increased inhibitory tone was observed over the 4-wk observation period. The result was driven by declining glutamate transporter expression (VGLUT1) in parallel with increasing GABA transporter expression (VGAT) over time, where a reactive VGAT+ astroglial subtype made an unexpected contribution to our findings.
Spatial attention during saccade decisions
Authors: Jonikaitis Donatas , Klapetek Anna , Deubel Heiner 
Published: March 2017

Behavioral measures of decision making are usually limited to observations of decision outcomes. In the present study, we made use of the fact that oculomotor and sensory selection are closely linked to track oculomotor decision making before oculomotor responses are made. We asked participants to make a saccadic eye movement to one of two memorized target locations and observed that visual sensitivity increased at both the chosen and the nonchosen saccade target locations, with a clear bias toward the chosen target. The time course of changes in visual sensitivity was related to saccadic latency, with the competition between the chosen and nonchosen targets resolved faster before short-latency saccades. On error trials, we observed an increased competition between the chosen and nonchosen targets. Moreover, oculomotor selection and visual sensitivity were influenced by top-down and bottom-up factors as well as by selection history and predicted the direction of saccades. Our findings demonstrate that saccade decisions have direct visual consequences and show that decision making can be traced in the human oculomotor system well before choices are made. Our results also indicate a strong association between decision making, saccade target selection, and visual sensitivity. NEW & NOTEWORTHY We show that saccadic decisions can be tracked by measuring spatial attention. Spatial attention is allocated in parallel to the two competing saccade targets, and the time course of spatial attention differs for fast-slow and for correct-erroneous decisions. Saccade decisions take the form of a competition between potential saccade goals, which is associated with spatial attention allocation to those locations.