CMPG1-dependent cell death follows perception of diverse pathogen elicitors at the host plasma membrane and is suppressed by Phytophthora infestans RXLR effector AVR3a

? Little is known about how effectors from filamentous eukaryotic plant pathogens manipulate host defences. Recently, Phytophthora infestans RXLR effector AVR3a has been shown to target and stabilize host E3 ligase CMPG1, which is required for programmed cell death (PCD) triggered by INF1. We investigated the involvement of CMPG1 in PCD elicited by perception of diverse pathogen proteins, and assessed whether AVR3a could suppress each. ? The role of CMPG1 in PCD events was investigated using virus-induced gene silencing, and the ability of AVR3a to suppress each was determined by transient expression of natural forms (AVR3a(KI) and AVR3a(EM)) and a mutated form, AVR3a(KI/Y147del) , which is unable to interact with or stabilize CMPG1. ? PCD triggered at the host plasma membrane by Cf-9/Avr9, Cf-4/Avr4, Pto/AvrPto or the oomycete pathogen-associated molecular pattern (PAMP), cellulose-binding elicitor lectin (CBEL), required CMPG1 and was suppressed by AVR3a, but not by the AVR3a(KI/Y147del) mutant. Conversely, PCD triggered by nucleotide-binding site-leucine-rich repeat (NBS-LRR) proteins R3a, R2 and Rx was independent of CMPG1 and unaffected by AVR3a. ? CMPG1-dependent PCD follows perception of diverse pathogen elicitors externally or in association with the inner surface of the host plasma membrane. We argue that AVR3a targets CMPG1 to block initial signal transduction/regulatory processes following pathogen perception at the plasma membrane.     

Effects of Prolonged Depolarization on the Nicotinic Acetylcholine Receptors of PC12 Cells

To determine whether prolonged depolarization and/or changes in intracellular Ca2+ concentrations stimulate adaptive responses of neuronal nicotinic acetylcholine receptors, PC12 pheochromocytoma cells were grown in medium containing various concentrations of K+. Nicotinic receptor function was determined as carbachol-stimulated uptake of 86Rb+. Cells were exposed to 50 mM K+ for up to 4 days and then allowed to repolarize for 60 min. Under these conditions, no changes in basal or carbachol-stimulated uptake of 86Rb+ were observed. Furthermore, neither the time course of carbachol-stimulated uptake or the carbachol concentration dependence of 86Rb+ uptake was altered. Finally, concurrent depolarization did not affect the functional down-regulation produced by chronic exposure of the cells to carbachol. Thus, neuronal nicotinic acetylcholine receptors on PC12 cells do not appear to be regulated by depolarization or prolonged elevation of the intracellular Ca2+ level.     

HIV Transmission in a State Prison System, 1988–2005

Introduction

HIV prevalence among state prison inmates in the United States is more than five times higher than among nonincarcerated persons, but HIV transmission within U.S. prisons is sparsely documented. We investigated 88 HIV seroconversions reported from 1988–2005 among male Georgia prison inmates.

Methods

We analyzed medical and administrative data to describe seroconverters'' HIV testing histories and performed a case-crossover analysis of their risks before and after HIV diagnosis. We sequenced the gag, env, and pol genes of seroconverters'' HIV strains to identify genetically-related HIV transmission clusters and antiretroviral resistance. We combined risk, genetic, and administrative data to describe prison HIV transmission networks.

Results

Forty-one (47%) seroconverters were diagnosed with HIV from July 2003–June 2005 when voluntary annual testing was offered. Seroconverters were less likely to report sex (OR [odds ratio] = 0.02, 95% CI [confidence interval]: 0–0.10) and tattooing (OR = 0.03, 95% CI: <0.01–0.20) in prison after their HIV diagnosis than before. Of 67 seroconverters'' specimens tested, 33 (49%) fell into one of 10 genetically-related clusters; of these, 25 (76%) reported sex in prison before their HIV diagnosis. The HIV strains of 8 (61%) of 13 antiretroviral-naïve and 21 (40%) of 52 antiretroviral-treated seroconverters were antiretroviral-resistant.

Discussion

Half of all HIV seroconversions were identified when routine voluntary testing was offered, and seroconverters reduced their risks following their diagnosis. Most genetically-related seroconverters reported sex in prison, suggesting HIV transmission through sexual networks. Resistance testing before initiating antiretroviral therapy is important for newly-diagnosed inmates.     

Prevention of estrogen-DNA adduct formation in MCF-10F cells by resveratrol

Resveratrol (Resv), a natural occurring phytolexin present in grapes and other foods, possesses chemopreventive effects revealed by its striking modulation of diverse cellular events associated with tumor initiation, promotion, and progression. Catechol estrogens generated in the metabolism of estrogens are oxidized to catechol quinones that react with DNA to form predominantly depurinating estrogen-DNA adducts. This event can generate the mutations responsible for cancer initiation. In this regard, Resv acts as both an antioxidant and an inducer of the phase II enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1). In this report, we present the effects of Resv on the metabolism of estrogens in normal breast epithelial cells (MCF-10F) treated with 4-hydroxyestradiol (4-OHE(2)) or estradiol-3,4-quinone (E(2)-3,4-Q). Resv induced NQO1 in a dose- and time-dependent manner, but did not affect the expression of catechol-O-methyltransferase. Ultraperformance liquid chromatography/tandem mass spectrometry was used to determine the effects of Resv on estrogen metabolism. Preincubation of the cells with Resv for 48 h decreased the formation of depurinating estrogen-DNA adducts from 4-OHE(2) or E(2)-3,4-Q and increased formation of methoxycatechol estrogens. When Resv was also present with the 4-OHE(2) or E(2)-3,4-Q, even greater increases in methoxycatechol estrogens were observed, and the DNA adducts were undetectable. We conclude that Resv can protect breast cells from carcinogenic estrogen metabolites, suggesting that it could be used in breast cancer prevention.     

Teaching medical students basic neurotransmitter pharmacology using primary research resources

Teaching pharmacology to medical students has long been seen as a challenge, and one to which a number of innovative approaches have been taken. In this article, we describe and evaluate the use of primary research articles in teaching second-year medical students both in terms of the information learned and the use of the papers themselves. We designed a seminar where small groups of students worked on different neurotransmitters before contributing information to a plenary session. Student feedback suggested that when the information was largely novel, students learned considerably more. Crucially, this improvement in knowledge was seen even when they had not directly studied a particular transmitter in their work groups, suggesting a shared learning experience. Moreover, the majority of students reported that using primary research papers was easy and useful, with over half stating that they would use them in future study.     

The dynamics of naturally acquired immune responses to Plasmodium falciparum sexual stage antigens Pfs230 & Pfs48/45 in a low endemic area in Tanzania

Background

Naturally acquired immune responses against sexual stages of P. falciparum can reduce the transmission of malaria from humans to mosquitoes. These antigens are candidate transmission-blocking vaccines but little is known about the acquisition of sexual stage immunity after exposure to gametocytes, or their longevity and functionality. We conducted a longitudinal study on functional sexual stage immune responses.

Methodology/Principal Findings

Parasitaemic individuals (n = 116) were recruited at a health centre in Lower Moshi, Tanzania. Patients presented with gametocytes (n = 16), developed circulating gametocytes by day 7 (n = 69) or between day 7 and 14 (n = 10) after treatment or did not develop gametocytes (n = 21). Serum samples were collected on the first day of gametocytaemia and 28 and 84 days post-enrolment (or d7, 28, 84 after enrolment from gametocyte-negative individuals). Antibody responses to sexual stage antigens Pfs230 and Pfs48/45 were detected in 20.7% (72/348) and 15.2% (53/348) of the samples, respectively, and were less prevalent than antibodies against asexual stage antigens MSP-1₁₉ (48.1%; 137/285) and AMA-1 (52.4%; 129/246)(p<0.001). The prevalence of anti-Pfs230 (p = 0.026) and anti-Pfs48/45 antibodies (p = 0.017) increased with longer duration of gametocyte exposure and had an estimated half-life of approximately 3 months. Membrane feeding experiments demonstrated a strong association between the prevalence and concentration of Pfs230 and Pfs48/45 antibodies and transmission reducing activity (TRA, p<0.01).

Conclusions/Significance

In a longitudinal study, anti-Pfs230 and Pf48/45 antibodies developed rapidly after exposure to gametocytes and were strongly associated with transmission-reducing activity. Our data indicate that the extent of antigen exposure is important in eliciting functional transmission-reducing immune responses.     

A Rapid Method for Characterization of Protein Relatedness Using Feature Vectors

We propose a feature vector approach to characterize the variation in large data sets of biological sequences. Each candidate sequence produces a single feature vector constructed with the number and location of amino acids or nucleic acids in the sequence. The feature vector characterizes the distance between the actual sequence and a model of a theoretical sequence based on the binomial and uniform distributions. This method is distinctive in that it does not rely on sequence alignment for determining protein relatedness, allowing the user to visualize the relationships within a set of proteins without making a priori assumptions about those proteins. We apply our method to two large families of proteins: protein kinase C, and globins, including hemoglobins and myoglobins. We interpret the high-dimensional feature vectors using principal components analysis and agglomerative hierarchical clustering. We find that the feature vector retains much of the information about the original sequence. By using principal component analysis to extract information from collections of feature vectors, we are able to quickly identify the nature of variation in a collection of proteins. Where collections are phylogenetically or functionally related, this is easily detected. Hierarchical agglomerative clustering provides a means of constructing cladograms from the feature vector output.