Translation initiation factor eIF1.2 promotes Toxoplasma stage conversion by regulating levels of key differentiation factors

The parasite Toxoplasma gondii persists in its hosts by converting from replicating tachyzoites to latent bradyzoites housed in tissue cysts. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a mutagenesis screen, we identified translation initiation factor eIF1.2 as a critical factor for T. gondii differentiation. A F97L mutation in eIF1.2 or the genetic ablation of eIF1.2 (∆eif1.2) markedly impeded bradyzoite cyst formation in vitro and in vivo. We demonstrated, at single-molecule level, that the eIF1.2 F97L mutation impacts the scanning process of the ribosome preinitiation complex on a model mRNA. RNA sequencing and ribosome profiling experiments unveiled that ∆eif1.2 parasites are defective in upregulating bradyzoite induction factors BFD1 and BFD2 during stress-induced differentiation. Forced expression of BFD1 or BFD2 significantly restored differentiation in ∆eif1.2 parasites. Together, our findings suggest that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish chronic toxoplasmosis.

Translation initiation factor eIF1.2 promotes Toxoplasma stage conversion by regulating levels of key differentiation factors

The parasite Toxoplasma gondii persists in its hosts by converting from replicating tachyzoites to latent bradyzoites housed in tissue cysts. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a mutagenesis screen, we identified translation initiation factor eIF1.2 as a critical factor for T. gondii differentiation. A F97L mutation in eIF1.2 or the genetic ablation of eIF1.2 (Δ eif1.2 ) markedly impeded bradyzoite cyst formation in vitro and in vivo . We demonstrated, at single-molecule level, that the eIF1.2 F97L mutation impacts the scanning process of the ribosome preinitiation complex on a model mRNA. RNA sequencing and ribosome profiling experiments unveiled that Δ eif1.2 parasites are defective in upregulating bradyzoite induction factors BFD1 and BFD2 during stress-induced differentiation. Forced expression of BFD1 or BFD2 significantly restored differentiation in Δ eif1.2 parasites. Together, our findings suggest that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish chronic toxoplasmosis.

Evaluation of topotecan and 10-hydroxycamptothecin on Toxoplasma gondii: Implications on baseline DNA damage and repair efficiency

Toxoplasma gondii is an obligate intracellular parasite in the phylum Apicomplexa that causes toxoplasmosis in humans and animals worldwide. Despite its prevalence, there is currently no effective vaccine or treatment for chronic infection. Although there are therapies against the acute stage, prolonged use is toxic and poorly tolerated. This study aims to explore the potential of repurposing topotecan and 10-hydroxycamptothecin (HCPT) as drugs producing double strand breaks (DSBs) in T. gondii. DSBs are mainly repaired by Homologous Recombination Repair (HRR) and Non-Homologous End Joining (NHEJ). Two T. gondii strains, RHΔHXGPRT and RHΔKU80, were used to compare the drug's effects on parasites. RHΔHXGPRT parasites may use both HRR and NHEJ pathways but RHΔKU80 lacks the KU80 protein needed for NHEJ, leaving only the HRR pathway. Here we demonstrate that topotecan and HCPT, both topoisomerase I venoms, affected parasite replication in a concentration-dependent manner. Moreover, variations in fluorescence intensity measurements for the H2A.X phosphorylation mark (γH2A.X), an indicator of DNA damage, were observed in intracellular parasites under drug treatment conditions. Interestingly, intracellular replicative parasites without drug treatment show a strong positive staining for γH2A.X, suggesting inherent DNA damage. Extracellular (non-replicating) parasites did not exhibit γH2A.X staining, indicating that the basal level of DNA damage is likely to be associated with replicative stress. A high rate of DNA replication stress possibly prompted the evolution of an efficient repair machinery in the parasite, making it an attractive target. Our findings show that topoisomerase 1 venoms are effective antiparasitics blocking T. gondii replication.

mRNA cap-binding protein eIF4E1 is a novel regulator of Toxoplasma gondii latency

The protozoan parasite Toxoplasma gondii causes serious opportunistic disease due to its ability to persist in patients as latent tissue cysts. The molecular mechanisms coordinating conversion between proliferative parasites (tachyzoites) and dormant cysts (bradyzoites) are not fully understood. We previously showed that phosphorylation of eIF2α accompanies bradyzoite formation, suggesting that this clinically relevant process involves regulation of mRNA translation. In this study, we investigated the composition and role of eIF4F multi-subunit complexes in translational control. Using CLIPseq, we find that the cap-binding subunit, eIF4E1, localizes to the 5'-end of all tachyzoite mRNAs, many of which show evidence of stemming from heterogenous transcriptional start sites. We further show that eIF4E1 operates as the predominant cap-binding protein in two distinct eIF4F complexes. Using genetic and pharmacological approaches, we found that eIF4E1 deficiency triggers efficient spontaneous formation of bradyzoites without stress induction. Consistent with this result, we also show that stress-induced bradyzoites exhibit reduced eIF4E1 expression. Overall, our findings establish a novel role for eIF4F in translational control required for parasite latency and microbial persistence.

A transcriptional network required for bradyzoite development in Toxoplasma gondii is dispensable for recrudescent disease

Identification of regulators of Toxoplasma gondii bradyzoite development and cyst formation is the most direct way to address the importance of parasite development in long-term persistence and reactivation of this parasite. Here we show that a T. gondii gene (named Regulator of Cystogenesis 1; ROCY1) is sufficient for T. gondii bradyzoite formation in vitro and in vivo. ROCY1 encodes an RNA binding protein that has a preference for 3' regulatory regions of hundreds of T. gondii transcripts, and its RNA-binding domains are required to mediate bradyzoite development. Female mice infected with ΔROCY1 parasites have reduced (>90%) cyst burden. While viable parasites can be cultivated from brain tissue for up to 6 months post-infection, chronic brain-resident ΔROCY1 parasites have reduced oral infectivity compared to wild type. Despite clear defects in bradyzoite formation and oral infectivity, ΔROCY1 parasites were able to reactivate with similar timing and magnitude as wild type parasites for up to 5 months post-infection. Therefore while ROCY1 is a critical regulator of the bradyzoite developmental pathway, it is not required for parasite reactivation, raising new questions about the persisting life stage responsible for causing recrudescent disease.

High-intensity home health physical therapy among older adult Veterans: A randomized controlled trial

BACKGROUND

Older adult Veterans are at high risk for adverse health outcomes following hospitalization. Since physical function is one of the largest potentially modifiable risk factors for adverse health outcomes, our purpose was to determine if progressive, high-intensity resistance training in home health physical therapy (PT) improves physical function in Veterans more than standardized home health PT and to determine if the high-intensity program was comparably safe, defined as having a similar number of adverse events.

METHODS

We enrolled Veterans and their spouses during an acute hospitalization who were recommended to receive home health care on discharge because of physical deconditioning. We excluded individuals who had contraindications to high-intensity resistance training. A total of 150 participants were randomized 1:1 to either (1) a progressive, high-intensity (PHIT) PT intervention or (2) a standardized PT intervention (comparison group). All participants in both groups were assigned to receive 12 visits (3 visits/week over 30 days) in their home. The primary outcome was gait speed at 60 days. Secondary outcomes included adverse events (rehospitalizations, emergency department visits, falls and deaths after 30 and 60-days), gait speed, Modified Physical Performance Test, Timed Up-and-Go, Short Physical Performance Battery, muscle strength, Life-Space Mobility assessment, Veterans RAND 12-item Health Survey, Saint Louis University Mental Status exam, and step counts at 30, 60, 90, 180 days post-randomization.

RESULTS

There were no differences between groups in gait speed at 60 days, and no significant differences in adverse events between groups at either time point. Similarly, physical performance measures and patient reported outcomes were not different at any time point. Notably, participants in both groups experienced increases in gait speed that met or exceeded established clinically important thresholds.

CONCLUSIONS

Among older adult Veterans with hospital-associated deconditioning and multimorbidity, high-intensity home health PT was safe and effective in improving physical function, but not found to be more effective than a standardized PT program.

Histone variant H2B.Z acetylation is necessary for maintenance of Toxoplasma gondii biological fitness

Through regulation of DNA packaging, histone proteins are fundamental to a wide array of biological processes. A variety of post-translational modifications (PTMs), including acetylation, constitute a proposed histone code that is interpreted by "reader" proteins to modulate chromatin structure. Canonical histones can be replaced with variant versions that add an additional layer of regulatory complexity. The protozoan parasite Toxoplasma gondii is unique among eukaryotes in possessing a novel variant of H2B designated H2B.Z. The combination of PTMs and the use of histone variants are important for gene regulation in T. gondii, offering new targets for drug development. In this work, T. gondii parasites were generated in which the 5 N-terminal acetylatable lysines in H2B.Z were mutated to either alanine (c-Myc-A) or arginine (c-Myc-R). The c-Myc-A mutant displayed no phenotype over than a mild defect in its ability to kill mice. The c-Myc-R mutant presented an impaired ability to grow and an increase in differentiation to latent bradyzoites. The c-Myc-R mutant was also more sensitive to DNA damage, displayed no virulence in mice, and provided protective immunity against future infection. While nucleosome composition was unaltered, key genes were abnormally expressed during in vitro bradyzoite differentiation. Our results show that regulation of the N-terminal positive charge patch of H2B.Z is important for these processes. We also show that acetylated N-terminal H2B.Z interacts with some unique proteins compared to its unacetylated counterpart; the acetylated peptide pulled down proteins associated with chromosome maintenance/segregation and cell cycle, suggesting a link between H2B.Z acetylation status and mitosis.

Histone variant H2B.Z acetylation is necessary for maintenance of Toxoplasma gondii biological fitness

Through regulation of DNA packaging, histone proteins are fundamental to a wide array of biological processes. A variety of post-translational modifications (PTMs), including acetylation, constitute a proposed histone code that is interpreted by "reader" proteins to modulate chromatin structure. Canonical histones can be replaced with variant versions that add an additional layer of regulatory complexity. The protozoan parasite Toxoplasma gondii is unique among eukaryotes in possessing a novel variant of H2B designated H2B.Z. The combination of PTMs and the use of histone variants is important for gene regulation in T. gondii, offering new targets for drug development. In this work, T. gondii parasites were generated in which the 5 N-terminal acetylatable lysines in H2B.Z were mutated to either alanine (c-Myc-A) or arginine (c-Myc-R). c-Myc-A mutant only displayed a mild effect in its ability to kill mice. c-Myc-R mutant presented an impaired ability to grow and an increase in differentiation to latent bradyzoites. This mutant line was also more sensitive to DNA damage, displayed no virulence in mice, and provided protective immunity against future infection. While nucleosome composition was unaltered, key genes were abnormally expressed during in vitro bradyzoite differentiation. Our results show that the N-terminal positive charge patch of H2B.Z is important for these procceses. Pull down assays with acetylated N-terminal H2B.Z peptide and unacetylated one retrieved common and differential interactors. Acetylated peptide pulled down proteins associated with chromosome maintenance/segregation and cell cycle, opening the question of a possible link between H2B.Z acetylation status and mitosis.

SPINE20 recommendations 2022: spine care-working together to recover stronger

PURPOSE

Globally, spine disorders are the leading cause of disability, affecting more than half a billion individuals. However, less than 50% of G20 countries specifically identify spine health within their public policy priorities. Therefore, it is crucial to raise awareness among policy makers of the disabling effect of spine disorders and their impact on the economic welfare of G20 nations. In 2019, SPINE20 was established as the leading advocacy group to bring global attention to spine disorders.

METHODS

Recommendations were developed through two Delphi methods with international and multi-professional panels.

RESULTS

In 2022, seven recommendations were delivered to the leaders of G20 countries, urging them to: Develop action plans to provide universal access to evidence-based spine care that incorporates the needs of minorities and vulnerable populations. Invest in the development of sustainable human resource capacity, through multisectoral and inter-professional competency-based education and training to promote evidence-based approaches to spine care, and to build an appropriate healthcare working environment that optimizes the delivery of safe health services. Develop policies using the best available evidence to properly manage spine disorders and to prolong functional healthy life expectancy in the era of an aging population. Create a competent workforce and improve the healthcare infrastructure/facilities including equipment to provide evidence-based inter-professional rehabilitation services to patients with spinal cord injury throughout their continuum of care. Build collaborative and innovative translational research capacity within national, regional, and global healthcare systems for state-of-the-art and cost-effective spine care across the healthcare continuum ensuring equality, diversity, and inclusion of all stakeholders. Develop international consensus statements on patient outcomes and how they can be used to define and develop pathways for value-based care. Recognize that intervening on determinants of health including physical activity, nutrition, physical and psychosocial workplace environment, and smoking-free lifestyle can reduce the burden of spine disabilities and improve the health status and wellness of the population. At the third SPINE20 summit 2022 which took place in Bali, Indonesia, in August 2022, 17 associations endorsed its recommendations.

CONCLUSION

SPINE20 advocacy efforts focus on developing public policy recommendations to improve the health, welfare, and wellness of all who suffer from spinal pain and disability. We propose that focusing on facilitating access to systems that prioritize value-based care delivered by a competent healthcare workforce will reduce disability and improve the productivity of the G20 nations.

SPINE20 recommendations 2021: spine care for people's health and prosperity

Purpose

The focus of SPINE20 is to develop evidence-based policy recommendations for the G20 countries to work with governments to reduce the burden of spine disease, and disability.

Methods

On September 17–18, 2021, SPINE20 held its annual meeting in Rome, Italy. Prior to the meeting, the SPINE20 created six proposed recommendations. These recommendations were uploaded to the SPINE20 website 10 days before the meeting and opened to the public for comments. The recommendations were discussed at the meeting allowing the participants to object and provide comments.

Results

In total, 27 societies endorsed the following recommendations. SPINE20 calls upon the G20 countries: (1) to expand telehealth for the access to spine care, especially in light of the current situation with COVID-19. (2) To adopt value-based interprofessional spine care as an approach to improve patient outcomes and reduce disability. (3) To facilitate access and invest in the development of a competent rehabilitation workforce to reduce the burden of disability related to spine disorders. (4) To adopt a strategy to promote daily physical activity and exercises among the elderly population to maintain an active and independent life with a healthy spine, particularly after COVID-19 pandemic. (5) To engage in capacity building with emerging countries and underserved communities for the benefit of spine patients. (6) To promote strategies to transfer evidence-based advances into patient benefit through effective implementation processes.

Conclusions

SPINE20’s initiatives will make governments and decision makers aware of efforts to reduce needless suffering from disabling spine pain through education that can be instituted across the globe.

Genome-wide localization of histone variants in Toxoplasma gondii implicates variant exchange in stage-specific gene expression

BACKGROUND

Toxoplasma gondii is a protozoan parasite that differentiates from acute tachyzoite stages to latent bradyzoite forms in response to environmental cues that modify the epigenome. We studied the distribution of the histone variants CenH3, H3.3, H2A.X, H2A.Z and H2B.Z, by genome-wide chromatin immunoprecipitation to understand the role of variant histones in developmental transitions of T. gondii parasites.

RESULTS

H3.3 and H2A.X were detected in telomere and telomere associated sequences, whereas H3.3, H2A.X and CenH3 were enriched in centromeres. Histones H2A.Z and H2B.Z colocalize with the transcriptional activation mark H3K4me3 in promoter regions surrounding the nucleosome-free region upstream of the transcription start site. The H2B.Z/H2A.Z histone pair also localizes to the gene bodies of genes that are silent but poised for activation, including bradyzoite stage-specific genes. The majority of H2A.X and H2A.Z/H2B.Z loci do not overlap, consistent with variant histones demarcating specific functional regions of chromatin. The extent of enrichment of H2A.Z/H2B.Z (and H3.3 and H2A.X) within the entire gene (5'UTR and gene body) reflects the timing of gene expression during the cell cycle, suggesting that dynamic turnover of H2B.Z/H2A.Z occurs during the tachyzoite cell cycle. Thus, the distribution of the variant histone H2A.Z/H2B.Z dimer defines active and developmentally silenced regions of the T. gondii epigenome including genes that are poised for expression.

CONCLUSIONS

Histone variants mark functional regions of parasite genomes with the dynamic placement of the H2A.Z/H2B.Z dimer implicated as an evolutionarily conserved regulator of parasite and eukaryotic differentiation.

Rebound of cyst number following discontinuation of guanabenz treatment for latent toxoplasmosis

Toxoplasma gondii is a protozoan parasite that causes opportunistic infection in immunocompromised individuals. The parasite forms latent tissue cysts that are refractory to current treatments and give rise to life-threatening reactivated infection following immune suppression. Previously, we showed that guanabenz sharply reduces brain cyst count in BALB/c mice harboring latent toxoplasmosis; however, whether cyst count would change once drug treatment stopped was not addressed. In the present study, we observed a rebound in brain cysts following the discontinuation of guanabenz or a guanabenz-pyrimethamine combination therapy. The re-expansion of brain cysts was not accompanied by symptoms of acute toxoplasmosis. We also tested whether the rebound in cyst counts could be ameliorated by administering pyrimethamine during or after guanabenz treatment.

Cervical fusion for treatment of degenerative conditions: development of appropriate use criteria

BACKGROUND CONTEXT

High quality evidence is difficult to generate, leaving substantial knowledge gaps in the treatment of spinal conditions. Appropriate use criteria (AUC) are a means of determining appropriate recommendations when high quality evidence is lacking.

PURPOSE

Define appropriate use criteria (AUC) of cervical fusion for treatment of degenerative conditions of the cervical spine.

STUDY DESIGN/SETTING

Appropriate use criteria for cervical fusion were developed using the RAND/UCLA appropriateness methodology. Following development of clinical guidelines and scenario writing, a one-day workshop was held with a multidisciplinary group of 14 raters, all considered thought leaders in their respective fields, to determine final ratings for cervical fusion appropriateness for various clinical situations.

OUTCOME MEASURES

Final rating for cervical fusion recommendation as either "Appropriate," "Uncertain" or "Rarely Appropriate" based on the median final rating among the raters.

METHODS

Inclusion criteria for scenarios included patients aged 18 to 80 with degenerative conditions of the cervical spine. Key modifiers were defined and combined to develop a matrix of clinical scenarios. The median score among the raters was used to determine the final rating for each scenario. The final rating was compared between modifier levels. Spearman's rank correlation between each modifier and the final rating was determined. A multivariable ordinal regression model was fit to determine the adjusted odds of an "Appropriate" final rating while adjusting for radiographic diagnosis, number of levels and symptom type. Three decision trees were developed using decision tree classification models and variable importance for each tree was computed.

RESULTS

Of the 263 scenarios, 47 (17.9 %) were rated as rarely appropriate, 66 (25%) as uncertain and 150 (57%) were rated as appropriate. Symptom type was the modifier most strongly correlated with the final rating (adjusted ρ2 = 0.58, p<.01). A multivariable ordinal regression adjusting for symptom type, diagnosis, and number of levels and showed high discriminative ability (C statistic = 0.90) and the adjusted odds ratio (aOR) of receiving a final rating of "Appropriate" was highest for myelopathy (aOR, 7.1) and radiculopathy (aOR, 4.8). Three decision tree models showed that symptom type and radiographic diagnosis had the highest variable importance.

CONCLUSIONS

Appropriate use criteria for cervical fusion in the setting of cervical degenerative disorders were developed. Symptom type was most strongly correlated with final rating. Myelopathy or radiculopathy were most strongly associated with an "Appropriate" rating, while axial pain without stenosis was most associated with "Rarely Appropriate."

Making it personal: science communication for the masses

To curtail the rising tide of antiscience threatening the health and progress of society, scientists are increasingly engaging with the public. Here, we describe our approach to write accessible books based on personal stories as a means to help spread scientific literacy to those who normally do not read science.

SPINE20 A global advocacy group promoting evidence-based spine care of value

PURPOSE

The Global Burden of Diseases (GBD) Studies have estimated that low back pain is one of the costliest ailments worldwide. Subsequent to GBD publications, leadership of the four largest global spine societies agreed to form SPINE20. This article introduces the concept of SPINE20, the recommendations, and the future of this global advocacy group linked to G20 annual summits.

METHODS

The founders of SPINE20 advocacy group coordinated with G20 Saudi Arabia to conduct the SPINE20 summit in 2020. The summit was intended to promote evidence-based recommendations to use the most reliable information from high-level research. Eight areas of importance to mitigate spine disorders were identified through a voting process of the participating societies. Twelve recommendations were discussed and vetted.

RESULTS

The areas of immediate concern were "Aging spine," "Future of spine care," "Spinal cord injuries," "Children and adolescent spine," "Spine-related disability," "Spine Educational Standards," "Patient safety," and "Burden on economy." Twelve recommendations were created and endorsed by 31/33 spine societies and 2 journals globally during a vetted process through the SPINE20.org website and during the virtual inaugural meeting November 10-11, 2020 held from the G20 platform.

CONCLUSIONS

This is the first time that international spine societies have joined to support actions to mitigate the burden of spine disorders across the globe. SPINE20 seeks to change awareness and treatment of spine pain by supporting local projects that implement value-based practices with healthcare policies that are culturally sensitive based on scientific evidence.

TgIF2K-B Is an eIF2α Kinase in Toxoplasma gondii That Responds to Oxidative Stress and Optimizes Pathogenicity

Toxoplasma gondii is an obligate intracellular parasite that persists in its vertebrate hosts in the form of dormant tissue cysts, which facilitate transmission through predation. The parasite must strike a balance that allows it to disseminate throughout its host without killing it, which requires the ability to properly counter host cell defenses. For example, oxidative stress encountered by Toxoplasma is suggested to impair parasite replication and dissemination. However, the strategies by which Toxoplasma mitigates oxidative stress are not yet clear. Among eukaryotes, environmental stresses induce the integrated stress response via phosphorylation of a translation initiation factor, eukaryotic initiation factor 2 (eIF2). Here, we show that the Toxoplasma eIF2 kinase TgIF2K-B is activated in response to oxidative stress and affords protection. Knockout of the TgIF2K-B gene, Δtgif2k-b, disrupted parasite responses to oxidative stresses and enhanced replication, diminishing the ability of the parasite to differentiate into tissue cysts. In addition, parasites lacking TgIF2K-B exhibited resistance to activated macrophages and showed greater virulence in an in vivo model of infection. Our results establish that TgIF2K-B is essential for Toxoplasma responses to oxidative stress, which are important for the parasite's ability to establish persistent infection in its host.IMPORTANCEToxoplasma gondii is a single-celled parasite that infects nucleated cells of warm-blooded vertebrates, including one-third of the human population. The parasites are not cleared by the immune response and persist in the host by converting into a latent tissue cyst form. Development of tissue cysts can be triggered by cellular stresses, which activate a family of TgIF2 kinases to phosphorylate the eukaryotic translation initiation factor TgIF2α. Here, we establish that the TgIF2 kinase TgIF2K-B is activated by oxidative stress and is critical for maintaining oxidative balance in the parasite. Depletion of TgIF2K-B alters gene expression, leading to accelerated growth and a diminished ability to convert into tissue cysts. This study establishes that TgIF2K-B is essential for the parasite's oxidative stress response and its ability to persist in the host as a latent infection.

Host sensing and signal transduction during Toxoplasma stage conversion

The intracellular parasite Toxoplasma gondii infects nucleated cells in virtually all warm-blooded vertebrates, including one-third of the human population. While immunocompetent hosts do not typically show symptoms of acute infection, parasites are retained in latent tissue cysts that can be reactivated upon immune suppression, potentially damaging key organ systems. Toxoplasma has a multistage life cycle that is intimately linked to environmental stresses and host signals. As this protozoan pathogen is transmitted between multiple hosts and tissues, it evaluates these external signals to appropriately differentiate into distinct life cycle stages, such as the transition from its replicative stage (tachyzoite) to the latent stage (bradyzoite) that persists as tissue cysts. Additionally, in the gut of its definitive host, felines, Toxoplasma converts into gametocytes that produce infectious oocysts (sporozoites) that are expelled into the environment. In this review, we highlight recent advances that have illuminated the interfaces between Toxoplasma and host and how these interactions control parasite stage conversion. Mechanisms underlying these stage transitions are important targets for therapeutic intervention aimed at thwarting parasite transmission and pathogenesis.

Biobehavioral Intervention Targeting Physical Activity Behavior Change for Older Veterans after Nontraumatic Amputation: A Randomized Controlled Trial

BACKGROUND

Lower-limb amputation (LLA) due to non-traumatic vascular etiology is linked to extremely low physical activity and high disability.

OBJECTIVE

To test the feasibility of a biobehavioral intervention designed to promote physical activity.

DESIGN

A randomized, single-blind feasibility trial with a crossover design.

SETTING

Veterans Administration Medical Center.

PARTICIPANTS

Military veterans (age: 65.7 [7.8] years; mean [standard deviation]) with nontraumatic lower-limb amputation (LLA), randomized to two groups: GROUP1 (n = 16) and GROUP2 (n = 15). Both groups had similar baseline amputation characteristics (level of amputation and time since amputation).

INTERVENTIONS

Twelve weekly, 30-minute telehealth sessions of physical activity behavior-change intervention, with GROUP1 participating in weeks 1-12 and GROUP2 in weeks 13-24. GROUP1 noncontact phase in weeks 13-24 and GROUP2 attention control telehealth phase in weeks 1-12.

MAIN OUTCOME MEASURES

Feasibility (participant retention, dose goal attainment, intervention acceptability [Intrinsic Motivation Inventory [IMI] Interest and Enjoyment scale], safety) and signal of efficacy (free-living physical activity [accelerometer-based average daily step count], Late Life Function and Disability Index - Disability Scale [LLFDI-DS]).

RESULTS

Participant retention rate was high (90%), with three participants lost to follow-up during the intervention period. Dose goal attainment was low, with only 10% of participants achieving an a priori walking dose goal. Intervention was rated as acceptable, with mean IMI Interest and Enjoyment score (5.8) statistically higher than the null value of 5.0 (P = .002). There were no between-group differences in adverse event rates (falls: P = .19, lower extremity wounds: P = .60). There was no signal of efficacy for change in average daily step count (d = -0.15) or LLFDI-DS (d = -0.22 and 0.17 for frequency and limitations scales, respectively).

CONCLUSIONS

Telehealth delivered biobehavioral intervention resulted in acceptable participant retention, low dose goal attainment, high participant acceptability, and low safety risk, while having no signal of efficacy (physical activity, disability) for people with nontraumatic LLA.

Emerging Therapeutic Targets Against Toxoplasma gondii: Update on DNA Repair Response Inhibitors and Genotoxic Drugs

Toxoplasma gondii is the causative agent of toxoplasmosis in animals and humans. This infection is transmitted to humans through oocysts released in the feces of the felines into the environment or by ingestion of undercooked meat. This implies that toxoplasmosis is a zoonotic disease and T. gondii is a foodborne pathogen. In addition, chronic toxoplasmosis in goats and sheep is the cause of recurrent abortions with economic losses in the sector. It is also a health problem in pets such as cats and dogs. Although there are therapies against this infection in its acute stage, they are not able to permanently eliminate the parasite and sometimes they are not well tolerated. To develop better, safer drugs, we need to elucidate key aspects of the biology of T. gondii. In this review, we will discuss the importance of the homologous recombination repair (HRR) pathway in the parasite's lytic cycle and how components of these processes can be potential molecular targets for new drug development programs. In that sense, the effect of different DNA damage agents or HHR inhibitors on the growth and replication of T. gondii will be described. Multitarget drugs that were either associated with other targets or were part of general screenings are included in the list, providing a thorough revision of the drugs that can be tested in other scenarios.

Toxoplasma gondii Co-opts the Unfolded Protein Response To Enhance Migration and Dissemination of Infected Host Cells

Toxoplasma gondii is an intracellular parasite that reconfigures its host cell to promote pathogenesis. One consequence of Toxoplasma parasitism is increased migratory activity of host cells, which facilitates dissemination. Here, we show that Toxoplasma triggers the unfolded protein response (UPR) in host cells through calcium release from the endoplasmic reticulum (ER). We further identify a novel role for the host ER stress sensor protein IRE1 in Toxoplasma pathogenesis. Upon infection, Toxoplasma activates IRE1, engaging its noncanonical role in actin remodeling through the binding of filamin A. By inducing cytoskeletal remodeling via IRE1 oligomerization in host cells, Toxoplasma enhances host cell migration in vitro and dissemination of the parasite to host organs in vivo Our study has identified novel mechanisms used by Toxoplasma to induce dissemination of infected cells, providing new insights into strategies for treatment of toxoplasmosis.IMPORTANCE Cells that are infected with the parasite Toxoplasma gondii exhibit heightened migratory activity, which facilitates dissemination of the infection throughout the body. In this report, we identify a new mechanism used by Toxoplasma to hijack its host cell and increase its mobility. We further show that the ability of Toxoplasma to increase host cell migration involves not the enzymatic activity of IRE1 but rather IRE1 engagement with actin cytoskeletal remodeling. Depletion of IRE1 from infected host cells reduces their migration in vitro and significantly hinders dissemination of Toxoplasma in vivo Our findings reveal a new mechanism underlying host-pathogen interactions, demonstrating how host cells are co-opted to spread a persistent infection around the body.

Evaluating the GCN5b bromodomain as a novel therapeutic target against the parasite Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite of great importance in human and veterinary health. The frontline treatment of antifolates suffers a variety of drawbacks, including toxicity and allergic reactions, underscoring the need to identify novel drug targets for new therapeutics to be developed. We previously showed that the Toxoplasma lysine acetyltransferase (KAT) GCN5b is an essential chromatin remodeling enzyme in the parasite linked to the regulation of gene expression. We have previously established that the KAT domain is a liability that can be targeted in the parasite by compounds like garcinol; here, we investigate the potential of the bromodomain as a targetable element of GCN5b. Bromodomains bind acetylated lysine residues on histones, which helps stabilize the KAT complex at gene promoters. Using an inducible dominant-negative strategy, we found that the GCN5b bromodomain is critical for Toxoplasma viability. We also found that the GCN5-family bromodomain inhibitor, L-Moses, interferes with the ability of the GCN5b bromodomain to associate with acetylated histone residues using an in vitro binding assay. Moreover, L-Moses displays potent activity against Toxoplasma tachyzoites in vitro, which can be overcome if parasites are engineered to over-express GCN5b. Collectively, our data support the GCN5b bromodomain as an attractive target for the development of new therapeutics.

Repositioning of Guanabenz in Conjugation with Gold and Silver Nanoparticles against Pathogenic Amoebae Acanthamoeba castellanii and Naegleria fowleri

Brain-eating amoebae cause devastating infections in the central nervous system of humans, resulting in a mortality rate of 95%. There are limited effective therapeutic options available clinically for treating granulomatous amoebic encephalitis and primary amoebic meningoencephalitis caused by Acanthamoeba castellanii (A. castellanii) and Naegleria fowleri (N. fowleri), respectively. Here, we report for the first time that guanabenz conjugated to gold and silver nanoparticles has significant antiamoebic activity against both A. castellanii and N. fowleri. Gold and silver conjugated guanabenz nanoparticles were synthesized by the one-phase reduction method and were characterized by ultraviolet-visible spectrophotometry and atomic force microscopy. Both metals were facilely stabilized by the coating of guanabenz, which was examined by surface plasmon resonance determination. The average size of gold nanoconjugated guanabenz was found to be 60 nm, whereas silver nanoparticles were produced in a larger size distribution with the average diameter of around 100 nm. Guanabenz and its noble metal nanoconjugates exhibited potent antiamoebic effects in the range of 2.5 to 100 μM against both amoebae. Nanoparticle conjugation enhanced the antiamoebic effects of guanabenz, as more potent activity was observed at a lower effective concentration (2.5 and 5 μM) compared to the drug alone. Moreover, encystation and excystation assays revealed that guanabenz inhibits the interconversion between the trophozoite and cyst forms of A. castellanii. Cysticdal effects against N. fowleri were also observed. Notably, pretreatment of A. castellanii with guanabenz and its nanoconjugates exhibited a significant reduction in the host cell cytopathogenicity from 65% to 38% and 2% in case of gold and silver nanoconjugates, respectively. Moreover, the cytotoxic evaluation of guanabenz and its nanoconjugates revealed negligible cytotoxicity against human cells. Guanabenz is already approved for hypertension and crosses the blood-brain barrier; the results of our current study suggest that guanabenz and its conjugated gold and silver nanoparticles can be repurposed as a potential drug for treating brain-eating amoebic infections.

Phosphorylation of eukaryotic initiation factor-2α in response to endoplasmic reticulum and nitrosative stress in the human protozoan parasite, Entamoeba histolytica

Entamoeba histolytica is an intestinal parasite infecting over 50 million people worldwide and is the causative agent of amebic dysentery and amoebic liver abscess. In the human host, E. histolytica experiences stress brought on by nutrient deprivation and the host immune response. To be a successful parasite, E. histolytica must counter the stress; therefore, understanding the stress response may uncover new drug targets. In many systems, the stress response includes down-regulation of protein translation, which is regulated by phosphorylation of eukaryotic initiation factor (eIF-2α). Previous work has demonstrated that phosphorylation of the E. histolytica eIF-2α (EheIF-2α) increases significantly when exposed to long-term serum starvation, oxidative stress, and long-term heat shock. However, the effects of reagents that are known to induce nitrosative or endoplasmic reticulum (ER) stresses, on EheIF-2α have yet to be evaluated. Nitrosative stress is part of the host's immune response and ER stress can be caused by several physiological or pathological factors. We treated E. histolytica cells with various reagents known to induce nitrosative stress (DPTA-NONOate and SNP) or ER stress (BFA and DTT). We examined the morphology of the ER, tracked phosphorylation of EheIF-2α, and assessed protein translation in control and stressed cells. While all four stress-inducing reagents caused a global reduction in protein translation, only DTT was capable of also inducing changes in the morphology of the ER (consistent with ER stress) and phosphorylation of EheIF-2α. This suggests that DTT authentically induces ER stress in E. histolytica and that this stress is managed by the eIF-2α-based system. This was supported by the observation that cells expressing a non-phosphorylatable version of eIF-2α were also highly sensitive to DTT-stress. Since protein translation decreased in the absence of phosphorylation of eIF-2α (after treatment with DPTA-NONOate, SNP or BFA), the data also indicate that there are alternative protein-translational control pathways in E. histolytica. Overall, our study further illuminates the stress response to nitrosative stress and ER stress in E. histolytica.

The utility of magnetic resonance imaging results in physician decision-making before initial lumbar spinal injection

BACKGROUND CONTEXT

The need for advanced imaging before spinal intervention is an area of ongoing debate. Many studies have demonstrated the accuracy of magnetic resonance imaging (MRI) results in evaluating structural pathology in the lumbar spine, but few have addressed how frequently MRI findings change clinical management. A randomized controlled trial showed that viewing MRI results did not impact outcomes in patients with radiculopathy undergoing epidural steroid injection (ESI). The results suggested ESIs that correlated with both imaging and clinical findings experienced slightly more benefit than the blinded cohort, although statistically insignificantly.

PURPOSE

Three related studies were conducted to (1) increase understanding of the opinions of interventional spine physicians regarding the utility of viewing imaging before injection and (2) evaluate the impact of viewing MRI results on injection planning (retrospective and prospective analyses).

STUDY DESIGN

Survey, prospective, and retrospective analysis.

PATIENT SAMPLE

Patients presenting to a university-based spine center for initial evaluation of back or leg pain who were candidates for spinal intervention.

OUTCOME MEASURES

Self-reported measures from a clinical practice questionnaire distributed to interventional spine physicians to determine rates and rationale for utilization of MRI before spine injection, physiologic measures including MRI results, functional measures including physician decision-making regarding type and location of injection performed.

METHODS

This study was funded by the University of Colorado Health and Welfare Trust. A survey was sent to interventional spine physicians to assess their utilization of MRI results before spine procedures. A retrospective analysis of patients who were candidates for ESI was conducted to evaluate how initial injection plan compared with the postviewing of MRI results on injection performed. In a prospective analysis, injection plans pre- and post-MRI were compared among patients presenting for initial evaluation of low back or leg pain.

RESULTS

Survey responses showed that specialists order MRI studies to correlate with physical exam (91%) and to detect the presence of synovial cysts (68%), whereas tumor/infection (93%) was most likely to cause a change in their approach. In the retrospective review, the physician's planned approach before viewing the MRI was concordant with the actual procedure 49% of the time. A different type of procedure was performed in 15% of planned injections. In such cases, the initial treatment plan was altered (ie, same procedure at a different or additional level or side) in 35% of planned injections. In the prospective data collection, 43% of injections were different from the initial physician decision. The most common reasons for altering the injection was different level affected (36%), facet pathology (22%), and different nerve root affected (16%).

CONCLUSIONS

In clinical practice, MRI before injection frequently changes management decisions in the planning and delivery of lumbar spine injections.

A novel GCN5b lysine acetyltransferase complex associates with distinct transcription factors in the protozoan parasite Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite that has a tremendous impact on human health and livestock. High seroprevalence among humans and other animals is facilitated by the conversion of rapidly proliferating tachyzoites into latent bradyzoites that are housed in tissue cysts, which allow transmission through predation. Epigenetic mechanisms contribute to the regulation of gene expression events that are crucial in both tachyzoites as well as their development into bradyzoites. Acetylation of histones is one of the critical histone modifications that is linked to active gene transcription. Unlike most early-branching eukaryotes, Toxoplasma possesses two GCN5 homologues, one of which, GCN5b, is essential for parasite viability. Surprisingly, GCN5b does not associate with most of the well-conserved proteins found in the GCN5 complexes of other eukaryotes. Of particular note is that GCN5b interacts with multiple putative transcription factors that have plant-like DNA-binding domains denoted as AP2. To understand the function of GCN5b and its role(s) in epigenetic gene regulation of stage switching, we performed co-immunoprecipitation of GCN5b under normal and bradyzoite induction conditions. We report the greatest resolution of the GCN5b complex to date under these various culture conditions. Moreover, reciprocal co-IPs were performed with distinct GCN5b-interacting AP2 factors (AP2IX-7 and AP2XII-4) to delineate the interactomes of each putative transcription factor. Our findings suggest that GCN5b is associated with at least two distinct complexes that are characterized by two different pairs of AP2 factors, and implicate up to four AP2 proteins to be involved with GCN5b-mediated gene regulation.

Regulation of arginine transport by GCN2 eIF2 kinase is important for replication of the intracellular parasite Toxoplasma gondii

Toxoplasma gondii is a prevalent protozoan parasite that can infect any nucleated cell but cannot replicate outside of its host cell. Toxoplasma is auxotrophic for several nutrients including arginine, tryptophan, and purines, which it must acquire from its host cell. The demands of parasite replication rapidly deplete the host cell of these essential nutrients, yet Toxoplasma successfully manages to proliferate until it lyses the host cell. In eukaryotic cells, nutrient starvation can induce the integrated stress response (ISR) through phosphorylation of an essential translation factor eIF2. Phosphorylation of eIF2 lowers global protein synthesis coincident with preferential translation of gene transcripts involved in stress adaptation, such as that encoding the transcription factor ATF4 (CREB2), which activates genes that modulate amino acid metabolism and uptake. Here, we discovered that the ISR is induced in host cells infected with Toxoplasma. Our results show that as Toxoplasma depletes host cell arginine, the host cell phosphorylates eIF2 via protein kinase GCN2 (EIF2AK4), leading to induced ATF4. Increased ATF4 then enhances expression of the cationic amino acid transporter CAT1 (SLC7A1), resulting in increased uptake of arginine in Toxoplasma-infected cells. Deletion of host GCN2, or its downstream effectors ATF4 and CAT1, lowers arginine levels in the host, impairing proliferation of the parasite. Our findings establish that Toxoplasma usurps the host cell ISR to help secure nutrients that it needs for parasite replication.

Parasites that live inside a host cell must develop strategies to ensure sufficient delivery of nutrients required for survival and replication. After invasion, Toxoplasma rapidly usurps the supply of its essential amino acid arginine from the host cell. Sensing low levels of arginine, the host cell initiates a nutrient starvation response designated the integrated stress response (ISR) that leads to enhanced expression of CAT1, a transporter that facilitates arginine uptake. Through activation of the host ISR and increased expression of this transporter, Toxoplasma secures a continued supply of arginine for its growth and reproduction. Inhibition of these pathways by therapeutic intervention could be a novel strategy to impair survival of the intracellular parasite.

Characterization of protein arginine methyltransferase of TgPRMT5 in Toxoplasma gondii

BACKGROUND

Protein arginine methylation is a prevalent post-translational modification. The protein arginine methyltransferase family (PRMT) is involved in many cellular processes in eukaryotes, including transcriptional regulation, epigenetic regulation, RNA metabolism, and DNA damage repair. Toxoplasma gondii, an opportunistic protozoan parasite, encodes five conserved PRMTs. PRMT5 is thought to be responsible for substantial PRMT activity in T. gondii; however, it has not yet been characterized.

METHODS

We tagged the 3' end of the endogenous TgPRMT5 genomic locus with sequence encoding a 3X hemagglutinin (HA) epitope. IFA and WB were performed to check the expression and subcellular localization of TgPRMT5 in tachyzoites and bradyzoites. In vitro methylation assays were performed to determine whether endogenous TgPRMT5 has arginine methyltransferase activity.

RESULTS

IFA and WB results showed that T. gondii PRMT5 (TgPRMT5) was localized in the cytoplasm in the tachyzoite stage; however, it shifts largely to the nuclear compartment in the bradyzoite stage. The in vitro methylation showed that TgPRMT5 has authentic type II PRMT activity and forms monomethylarginines and symmetric dimethylarginines.

CONCLUSIONS

We determined the expression and cellular localization of TgPRMT5 in tachyzoites and bradyzoites and confirmed its type II PRMT activity. We demonstrated the major changes in expression and cellular localization of TgPRMT5 during the tachyzoite and bradyzoite stages in T. gondii. Our findings suggest that TgPRMT5 protein may be involved in tachyzoite-bradyzoite transformation.

Evaluation of ATM Kinase Inhibitor KU-55933 as Potential Anti-Toxoplasma gondii Agent

Toxoplasma gondii is an apicomplexan protozoan parasite with a complex life cycle composed of multiple stages that infect mammals and birds. Tachyzoites rapidly replicate within host cells to produce acute infection during which the parasite disseminates to tissues and organs. Highly replicative cells are subject to Double Strand Breaks (DSBs) by replication fork collapse and ATM, a member of the phosphatidylinositol 3-kinase (PI3K) family, is a key factor that initiates DNA repair and activates cell cycle checkpoints. Here we demonstrate that the treatment of intracellular tachyzoites with the PI3K inhibitor caffeine or ATM kinase-inhibitor KU-55933 affects parasite replication rate in a dose-dependent manner. KU-55933 affects intracellular tachyzoite growth and induces G1-phase arrest. Addition of KU-55933 to extracellular tachyzoites also leads to a significant reduction of tachyzoite replication upon infection of host cells. ATM kinase phosphorylates H2A.X (γH2AX) to promote DSB damage repair. The level of γH2AX increases in tachyzoites treated with camptothecin (CPT), a drug that generates fork collapse, but this increase was not observed when co-administered with KU-55933. These findings support that KU-55933 is affecting the Toxoplasma ATM-like kinase (TgATM). The combination of KU-55933 and other DNA damaging agents such as methyl methane sulfonate (MMS) and CPT produce a synergic effect, suggesting that TgATM kinase inhibition sensitizes the parasite to damaged DNA. By contrast, hydroxyurea (HU) did not further inhibit tachyzoite replication when combined with KU-55933.

Improving Physical Activity Through Adjunct Telerehabilitation Following Total Knee Arthroplasty: Randomized Controlled Trial Protocol

Background

Physical activity remains low and nearly unchanged from preoperative levels following total knee arthroplasty (TKA), and this is thought to underlie long-term functional limitations, secondary health problems, and higher health care costs after TKA.

Objective

Our objective is to determine whether a telehealth-based intervention could improve physical activity and functional outcomes after TKA.

Design

The design is a 2-arm, parallel, assessor-blinded, randomized controlled trial with baseline, midintervention, postintervention, and 6-month follow-up assessments.

Setting

The setting is one academic medical center and one Veterans Affairs health care system.

Participants

One hundred US military veterans (aged 50-85 years) scheduled for unilateral TKA will participate in this study.

Intervention

The telehealth-based intervention to change physical activity behavior will be delivered through 10 sessions each of 30 minutes over a 12-week period. Participants will be provided with a wearable physical activity monitor to receive feedback on step count and guide goal-setting. Control participants will receive telehealth-based education on nonbehavioral aspects of health for the same frequency and duration as the intervention group. For both groups, telehealth sessions will occur concurrently with standardized outpatient rehabilitation.

Measurements

The primary outcome will be change in physical activity, assessed as daily step counts measured using an accelerometer-based sensor. Secondary outcomes will be measured using the Life-Space Assessment questionnaire and change in physical function (30-Second Chair-Stand Test, Timed "Up & Go" Test, Six-Minute Walk Test, Western Ontario and McMaster Universities Osteoarthritis Index, and Veterans RAND 12-Item Health Survey).

Limitations

Participant and interventionist blinding is not possible.

Conclusions

This trial will assess the efficacy of a novel behavior-change intervention to improve physical activity and physical function in patients after TKA. Effective physical activity behavior change could provide clinicians with a technique to augment current practice and resolve poor physical activity outcomes, long-term health problems, and high costs following TKA.

TgDrpC, an atypical dynamin-related protein in Toxoplasma gondii, is associated with vesicular transport factors and parasite division

Dynamin-related proteins (Drps) are involved in diverse processes such as organelle division and vesicle trafficking. The intracellular parasite Toxoplasma gondii possesses three distinct Drps. TgDrpC, whose function remains unresolved, is unusual in that it lacks a conserved GTPase Effector Domain, which is typically required for function. Here, we show that TgDrpC localizes to cytoplasmic puncta; however, in dividing parasites, TgDrpC redistributes to the growing edge of the daughter cells. By conditional knockdown, we determined that loss of TgDrpC stalls division and leads to rapid deterioration of multiple organelles and the IMC. We also show that TgDrpC interacts with proteins that exhibit homology to those involved in vesicle transport, including members of the adaptor complex 2. Two of these proteins, a homolog of the adaptor protein 2 (AP-2) complex subunit alpha-1 and a homolog of the ezrin-radixin-moesin (ERM) family proteins, localize to puncta and associate with the daughter cells. Consistent with the association with vesicle transport proteins, re-distribution of TgDrpC to the IMC during division is dependent on post-Golgi trafficking. Together, these results support that TgDrpC contributes to vesicle trafficking and is critical for stability of parasite organelles and division.

Extracellular Matrix Remodeling Regulates Glucose Metabolism through TXNIP Destabilization

The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix (ECM) remodeling as another fundamental node of cell-extrinsic metabolic regulation. Unbiased analysis of glycolytic drivers identified the hyaluronan-mediated motility receptor as being among the most highly correlated with glycolysis in cancer. Confirming a mechanistic link between the ECM component hyaluronan and metabolism, treatment of cells and xenografts with hyaluronidase triggers a robust increase in glycolysis. This is largely achieved through rapid receptor tyrosine kinase-mediated induction of the mRNA decay factor ZFP36, which targets TXNIP transcripts for degradation. Because TXNIP promotes internalization of the glucose transporter GLUT1, its acute decline enriches GLUT1 at the plasma membrane. Functionally, induction of glycolysis by hyaluronidase is required for concomitant acceleration of cell migration. This interconnection between ECM remodeling and metabolism is exhibited in dynamic tissue states, including tumorigenesis and embryogenesis.

A latent ability to persist: differentiation in Toxoplasma gondii

A critical factor in the transmission and pathogenesis of Toxoplasma gondii is the ability to convert from an acute disease-causing, proliferative stage (tachyzoite), to a chronic, dormant stage (bradyzoite). The conversion of the tachyzoite-containing parasitophorous vacuole membrane into the less permeable bradyzoite cyst wall allows the parasite to persist for years within the host to maximize transmissibility to both primary (felids) and secondary (virtually all other warm-blooded vertebrates) hosts. This review presents our current understanding of the latent stage, including the factors that are important in bradyzoite induction and maintenance. Also discussed are the recent studies that have begun to unravel the mechanisms behind stage switching.

Transcriptional repression by ApiAP2 factors is central to chronic toxoplasmosis

Tachyzoite to bradyzoite development in Toxoplasma is marked by major changes in gene expression resulting in a parasite that expresses a new repertoire of surface antigens hidden inside a modified parasitophorous vacuole called the tissue cyst. The factors that control this important life cycle transition are not well understood. Here we describe an important transcriptional repressor mechanism controlling bradyzoite differentiation that operates in the tachyzoite stage. The ApiAP2 factor, AP2IV-4, is a nuclear factor dynamically expressed in late S phase through mitosis/cytokinesis of the tachyzoite cell cycle. Remarkably, deletion of the AP2IV-4 locus resulted in the expression of a subset of bradyzoite-specific proteins in replicating tachyzoites that included tissue cyst wall components BPK1, MCP4, CST1 and the surface antigen SRS9. In the murine animal model, the mis-timing of bradyzoite antigens in tachyzoites lacking AP2IV-4 caused a potent inflammatory monocyte immune response that effectively eliminated this parasite and prevented tissue cyst formation in mouse brain tissue. Altogether, these results indicate that suppression of bradyzoite antigens by AP2IV-4 during acute infection is required for Toxoplasma to successfully establish a chronic infection in the immune-competent host.

The Toxoplasma biology that underlies the establishment of a chronic infection is developmental conversion of the acute tachyzoite stage into the latent bradyzoite-tissue cyst stage. Despite the important clinical consequences of this developmental pathway, the molecular basis of the switch mechanisms that control formation of the tissue cyst is still poorly understood. A fundamental feature of tissue cyst formation is the expression of bradyzoite-specific genes. Here we show the transcription factor AP2IV-4 directly silences bradyzoite mRNA and protein expression in the acute tachyzoite stage demonstrating that developmental control of tissue cyst formation is as much about when not to express bradyzoite genes as it is about when to activate them. Losing the suppression of bradyzoite gene expression in the acute tachyzoite stage caused by deleting AP2IV-4 blocked the establishment of chronic disease in healthy animals via increased protective immunity suggesting a possible strategy for preventing chronic Toxoplasma infections.

Autophagy participates in the unfolded protein response in Toxoplasma gondii

Environmental and genetic perturbations of endoplasmic reticulum (ER) function can lead to the accumulation of unfolded proteins. In these conditions, eukaryotic cells can activate a complex signaling network called the unfolded protein response (UPR) to reduce ER stress and restore cellular homeostasis. Autophagy, a degradation and recycling process, is part of this response. The parasitic protist Toxoplasma gondii is known to be able to activate the UPR upon ER stress, and we now show that this pathway leads to autophagy activation, supporting the idea of a regulated function for canonical autophagy as part of an integrated stress response in the parasites.

Elp3 and RlmN: A tale of two mitochondrial tail-anchored radical SAM enzymes in Toxoplasma gondii

Radical S-adenosylmethionine (rSAM) enzymes use a 5'-deoxyadensyl 5'-radical to methylate a wide array of diverse substrates including proteins, lipids and nucleic acids. One such enzyme, Elongator protein-3 (TgElp3), is an essential protein in Toxoplasma gondii, a protozoan parasite that can cause life-threatening opportunistic disease. Unlike Elp3 homologues which are present in all domains of life, TgElp3 localizes to the outer mitochondrial membrane (OMM) via a tail-anchored trafficking mechanism in Toxoplasma. Intriguingly, we identified a second tail-anchored rSAM domain containing protein (TgRlmN) that also localizes to the OMM. The transmembrane domain (TMD) on Toxoplasma Elp3 and RlmN homologues is required for OMM localization and has not been seen beyond the chromalveolates. Both TgElp3 and TgRlmN contain the canonical rSAM amino acid sequence motif (CxxxCxxC) necessary to form the 4Fe-4S cluster required for tRNA modifications. In E. coli, RlmN is responsible for the 2-methlyadenosine (m2A) synthesis at purine 37 in tRNA while in S. cerevisiae, Elp3 is necessary for the formation of 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) at the wobble tRNA position. To investigate why these two rSAM enzymes localize to the mitochondrion in Toxoplasma, and whether or not TgRlmN and TgElp3 possess tRNA methyltransferase activity, a series of mutational and biochemical studies were performed. Overexpression of either TgElp3 or TgRlmN resulted in a significant parasite replication defect, but overexpression was tolerated if either the TMD or rSAM domain was mutated. Furthermore, we show the first evidence that Toxoplasma tRNAGlu contains the mcm5s2U modification, which is the putative downstream product generated by TgElp3 activity.

Transient Hypokalemic Quadriplegia After a Lumbar Transforaminal Epidural Dexamethasone Injection: A Case Report

A 30-year-old man with no significant medical history presented with hypokalemic quadriplegia 4 hours after he received a lumbar transforaminal epidural steroid injection (ESI) containing dexamethasone and lidocaine. A comprehensive workup ruled out acquired and hereditary causes of hypokalemic paralysis. Symptoms gradually resolved within hours after potassium restoration with no residual neurologic deficits. Paralysis after transforaminal ESI is uncommon but has been associated with particulate steroids that can coalesce into aggregates and occlude vessels. To our knowledge, there have been no case reports of paralysis after ESI with dexamethasone, a nonparticulate steroid. This transient paralysis is possibly caused by the effects of glucocorticoids on Na-K channels and insulin resistance resulting in hyperglycemia and subsequent hypokalemia. We reviewed the differential diagnosis of transient paralysis after epidural steroid injection in this report.

LEVEL OF EVIDENCE

IV.

The common parasite Toxoplasma gondii induces prostatic inflammation and microglandular hyperplasia in a mouse model

BACKGROUND

Inflammation is the most prevalent and widespread histological finding in the human prostate, and associates with the development and progression of benign prostatic hyperplasia and prostate cancer. Several factors have been hypothesized to cause inflammation, yet the role each may play in the etiology of prostatic inflammation remains unclear. This study examined the possibility that the common protozoan parasite Toxoplasma gondii induces prostatic inflammation and reactive hyperplasia in a mouse model.

METHODS

Male mice were infected systemically with T. gondii parasites and prostatic inflammation was scored based on severity and focality of infiltrating leukocytes and epithelial hyperplasia. We characterized inflammatory cells with flow cytometry and the resulting epithelial proliferation with bromodeoxyuridine (BrdU) incorporation.

RESULTS

We found that T. gondii infects the mouse prostate within the first 14 days of infection and can establish parasite cysts that persist for at least 60 days. T. gondii infection induces a substantial and chronic inflammatory reaction in the mouse prostate characterized by monocytic and lymphocytic inflammatory infiltrate. T. gondii-induced inflammation results in reactive hyperplasia, involving basal and luminal epithelial proliferation, and the exhibition of proliferative inflammatory microglandular hyperplasia in inflamed mouse prostates.

CONCLUSIONS

This study identifies the common parasite T. gondii as a new trigger of prostatic inflammation, which we used to develop a novel mouse model of prostatic inflammation. This is the first report that T. gondii chronically encysts and induces chronic inflammation within the prostate of any species. Furthermore, T. gondii-induced prostatic inflammation persists and progresses without genetic manipulation in mice, offering a powerful new mouse model for the study of chronic prostatic inflammation and microglandular hyperplasia.

Targeting of tail-anchored membrane proteins to subcellular organelles in Toxoplasma gondii

Proper protein localization is essential for critical cellular processes, including vesicle-mediated transport and protein translocation. Tail-anchored (TA) proteins are integrated into organellar membranes via the C-terminus, orienting the N-terminus towards the cytosol. Localization of TA proteins occurs posttranslationally and is governed by the C-terminus, which contains the integral transmembrane domain (TMD) and targeting sequence. Targeting of TA proteins is dependent on the hydrophobicity of the TMD as well as the length and composition of flanking amino acid sequences. We previously identified an unusual homologue of elongator protein, Elp3, in the apicomplexan parasite Toxoplasma gondii as a TA protein targeting the outer mitochondrial membrane. We sought to gain further insight into TA proteins and their targeting mechanisms using this early-branching eukaryote as a model. Our bioinformatics analysis uncovered 59 predicted TA proteins in Toxoplasma, 9 of which were selected for follow-up analyses based on representative features. We identified novel TA proteins that traffic to specific organelles in Toxoplasma, including the parasite endoplasmic reticulum, mitochondrion, and Golgi apparatus. Domain swap experiments elucidated that targeting of TA proteins to these specific organelles was strongly influenced by the TMD sequence, including charge of the flanking C-terminal sequence.

Phosphorylation of Eukaryotic Initiation Factor-2α during Stress and Encystation in Entamoeba Species

Entamoeba histolytica is an enteric pathogen responsible for amoebic dysentery and liver abscess. It alternates between the host-restricted trophozoite form and the infective environmentally-stable cyst stage. Throughout its lifecycle E. histolytica experiences stress, in part, from host immune pressure. Conversion to cysts is presumed to be a stress-response. In other systems, stress induces phosphorylation of a serine residue on eukaryotic translation initiation factor-2α (eIF2α). This inhibits eIF2α activity resulting in a general decline in protein synthesis. Genomic data reveal that E. histolytica possesses eIF2α (EheIF2α) with a conserved phosphorylatable serine at position 59 (Ser⁵⁹). Thus, this pathogen may have the machinery for stress-induced translational control. To test this, we exposed cells to different stress conditions and measured the level of total and phospho-EheIF2α. Long-term serum starvation, long-term heat shock, and oxidative stress induced an increase in the level of phospho-EheIF2α, while short-term serum starvation, short-term heat shock, or glucose deprivation did not. Long-term serum starvation also caused a decrease in polyribosome abundance, which is in accordance with the observation that this condition induces phosphorylation of EheIF2α. We generated transgenic cells that overexpress wildtype EheIF2α, a non-phosphorylatable variant of eIF2α in which Ser⁵⁹ was mutated to alanine (EheIF2α-S59A), or a phosphomimetic variant of eIF2α in which Ser⁵⁹ was mutated to aspartic acid (EheIF2α-S59D). Consistent with the known functions of eIF2α, cells expressing wildtype or EheIF2α-S59D exhibited increased or decreased translation, respectively. Surprisingly, cells expressing EheIF2α-S59A also exhibited reduced translation. Cells expressing EheIF2α-S59D were more resistant to long-term serum starvation underscoring the significance of EheIF2α phosphorylation in managing stress. Finally, phospho-eIF2α accumulated during encystation in E. invadens, a model encystation system. Together, these data demonstrate that the eIF2α-dependent stress response system is operational in Entamoeba species.

Entamoeba histolytica is the causative agent of amoebic dysentery and liver abscess and is prevalent in underdeveloped countries that lack proper sanitation. Infection is acquired by ingestion of the cyst form in contaminated food or water. During infection, the parasite experiences stress including demanding growth conditions and host immune pressure. Conversion to the infective cyst may be induced by such stress. In other organisms, stress causes a decrease in protein biosynthesis by inducing phosphorylation of eIF2α, which participates in translation initiation. We exposed E. histolytica to six different stress conditions and observed that some of these conditions (long-term serum starvation, long-term heat shock, and oxidative stress) induced an increase in the level of phospho-eIF2α. Long-term serum starvation was also accompanied by a decrease in mRNA translation. A cell line expressing a mutant version of eIF2α that behaves as a phosphomimetic exhibited decreased translation and increased survival during long-term serum starvation. Finally, phospho-eIF2α accumulated in cysts of E. invadens, a reptilian pathogen that readily encysts in vitro. Together, these data demonstrate that the eIF2α-dependent stress response system is operational in Entamoeba and may regulate encystation.

Preventing friendly fire in the war on microbes

Lung injury induced by Pseudomonas aeruginosa infection might be subverted by targeting a chromatin-remodeling protein (Zou et al., this issue).

The cytoplasmic prolyl-tRNA synthetase of the malaria parasite is a dual-stage target of febrifugine and its analogs

The emergence of drug resistance is a major limitation of current antimalarials. The discovery of new druggable targets and pathways including those that are critical for multiple life cycle stages of the malaria parasite is a major goal for developing next-generation antimalarial drugs. Using an integrated chemogenomics approach that combined drug resistance selection, whole-genome sequencing, and an orthogonal yeast model, we demonstrate that the cytoplasmic prolyl-tRNA (transfer RNA) synthetase (PfcPRS) of the malaria parasite Plasmodium falciparum is a biochemical and functional target of febrifugine and its synthetic derivative halofuginone. Febrifugine is the active principle of a traditional Chinese herbal remedy for malaria. We show that treatment with febrifugine derivatives activated the amino acid starvation response in both P. falciparum and a transgenic yeast strain expressing PfcPRS. We further demonstrate in the Plasmodium berghei mouse model of malaria that halofuginol, a new halofuginone analog that we developed, is active against both liver and asexual blood stages of the malaria parasite. Halofuginol, unlike halofuginone and febrifugine, is well tolerated at efficacious doses and represents a promising lead for the development of dual-stage next-generation antimalarials.

An ensemble of specifically targeted proteins stabilizes cortical microtubules in the human parasite Toxoplasma gondii

The human parasite Toxoplasma gondii has 22 regularly spaced microtubules associated with the cortex. This work defines the differential localization of associated proteins, explores the biophysical constraints on specific targeting along the cortical microtubules, and investigates the function of these proteins in stabilizing the polymers.

Although all microtubules within a single cell are polymerized from virtually identical subunits, different microtubule populations carry out specialized and diverse functions, including directional transport, force generation, and cellular morphogenesis. Functional differentiation requires specific targeting of associated proteins to subsets or even subregions of these polymers. The cytoskeleton of Toxoplasma gondii, an important human parasite, contains at least five distinct tubulin-based structures. In this work, we define the differential localization of proteins along the cortical microtubules of T. gondii, established during daughter biogenesis and regulated by protein expression and exchange. These proteins distinguish cortical from mitotic spindle microtubules, even though the assembly of these subsets is contemporaneous during cell division. Finally, proteins associated with cortical microtubules collectively protect the stability of the polymers with a remarkable degree of functional redundancy.

The metabolic milieu of metastases

To colonize the liver, colon cancer metastases must overcome hypoxia and other metabolic stress. Loo et al. now show that metastatic cells achieve this by decreasing miR-483 and miR-551a expression, which derepresses creatine kinase expression and allows energy to be captured from extracellular ATP through generation and import of phosphocreatine.

Proteome-wide lysine acetylation in cortical astrocytes and alterations that occur during infection with brain parasite Toxoplasma gondii

Lysine acetylation is a reversible post-translational modification (PTM) that has been detected on thousands of proteins in nearly all cellular compartments. The role of this widespread PTM has yet to be fully elucidated, but can impact protein localization, interactions, activity, and stability. Here we present the first proteome-wide survey of lysine acetylation in cortical astrocytes, a subtype of glia that is a component of the blood-brain barrier and a key regulator of neuronal function and plasticity. We identified 529 lysine acetylation sites across 304 proteins found in multiple cellular compartments that largely function in RNA processing/transcription, metabolism, chromatin biology, and translation. Two hundred and seventy-seven of the acetylated lysines we identified on 186 proteins have not been reported previously in any other cell type. We also mapped an acetylome of astrocytes infected with the brain parasite, Toxoplasma gondii. It has been shown that infection with T. gondii modulates host cell gene expression, including several lysine acetyltransferase (KAT) and deacetylase (KDAC) genes, suggesting that the host acetylome may also be altered during infection. In the T. gondii-infected astrocytes, we identified 34 proteins exhibiting a level of acetylation >2-fold and 24 with a level of acetylation <2-fold relative to uninfected astrocytes. Our study documents the first acetylome map for cortical astrocytes, uncovers novel lysine acetylation sites, and demonstrates that T. gondii infection produces an altered acetylome.

Canonical histone H2Ba and H2A.X dimerize in an opposite genomic localization to H2A.Z/H2B.Z dimers in Toxoplasma gondii

Histone H2Ba of Toxoplasma gondii was expressed as recombinant protein (rH2Ba) and used to generate antibody in mouse that is highly specific. Antibody recognizing rH2Ba detects a single band in tachyzoite lysate of the expected molecular weight (12kDa). By indirect immunofluorescence (IFA) in in vitro grown tachyzoites and bradyzoites, the signal was detected only in the parasite nucleus. The nucleosome composition of H2Ba was determined through co-immunoprecipitation assays. H2Ba was detected in the same immunocomplex as H2A.X, but not with H2A.Z. Through chromatin immunoprecipitation (ChIP) assays and qPCR, it was observed that H2Ba is preferentially located at promoters of inactive genes and silent regions, accompanying H2A.X and opposed to H2A.Z/H2B.Z dimers.

Characterization of TgPuf1, a member of the Puf family RNA-binding proteins from Toxoplasma gondii

Background

Puf proteins act as translational regulators and affect many cellular processes in a wide range of eukaryotic organisms. Although Puf proteins have been well characterized in many model systems, little is known about the structural and functional characteristics of Puf proteins in the parasite Toxoplasma gondii.

Methods

Using a combination of conventional molecular approaches, we generated endogenous TgPuf1 tagged with hemagglutinin (HA) epitope and investigated the TgPuf1 expression levels and localization in the tachyzoites and bradyzoites. We used RNA Electrophoretic Mobility Shfit Assay (EMSA) to determine whether the recombination TgPuf1 has conserverd RNA binding activity and specificity.

Results

TgPuf1 was expressed at a significantly higher level in bradyzoites than in tachyzoites. TgPuf1 protein was predominantly localized within the cytoplasm and showed a much more granular cytoplasmic staining pattern in bradyzoites. The recombinant Puf domain of TgPuf1 showed strong binding affinity to two RNA fragments containing Puf-binding motifs from other organisms as artificial target sequences. However, two point mutations in the core Puf-binding motif resulted in a significant reduction in binding affinity, indicating that TgPuf1 also binds to conserved Puf-binding motif.

Conclusions

TgPuf1 appears to exhibit different expression levels in the tachyzoites and bradyzoites, suggesting that TgPuf1 may function in regulating the proliferation or/and differentiation that are important in providing parasites with the ability to respond rapidly to changes in environmental conditions. This study provides a starting point for elucidating the function of TgPuf1 during parasite development.