Invasion of Toxoplasma gondii bradyzoites: Molecular dissection of the moving junction proteins and effective vaccination targets.

Toxoplasmosis is a neglected parasitic disease necessitating public health control. Host cell invasion by Toxoplasma occurs at different stages of the parasite's life cycle and is crucial for survival and establishment of infection. In tachyzoites, which are responsible for acute toxoplasmosis, invasion involves the formation of a molecular bridge between the parasite and host cell membranes, referred to as the moving junction (MJ). The MJ is shaped by the assembly of AMA1 and RON2, as part of a complex involving additional RONs. While this essential process is well characterized in tachyzoites, the invasion process remains unexplored in bradyzoites, which form cysts and are responsible for chronic toxoplasmosis and contribute to the dissemination of the parasite between hosts. Here, we show that bradyzoites invade host cells in an MJ-dependent fashion but differ in protein composition from the tachyzoite MJ, relying instead on the paralogs AMA2 and AMA4. Functional characterization of AMA4 reveals its key role for cysts burden during the onset of chronic infection, while being dispensable for the acute phase. Immunizations with AMA1 and AMA4, alone or in complex with their rhoptry neck respective partners RON2 and RON2L1, showed that the AMA1-RON2 pair induces strong protection against acute and chronic infection, while the AMA4-RON2L1 complex targets more selectively the chronic form. Our study provides important insights into the molecular players of bradyzoite invasion and indicates that invasion of cyst-forming bradyzoites contributes to cyst burden. Furthermore, we validate AMA-RON complexes as potential vaccine candidates to protect against toxoplasmosis.

In vivo antagonistic role of the Human T-Cell Leukemia Virus Type 1 regulatory proteins Tax and HBZ.

Adult T cell leukemia (ATL) is an aggressive malignancy secondary to chronic infection by the human T-cell leukemia virus type 1 (HTLV-1) infection. Two viral proteins, Tax and HBZ, play central roles in ATL leukemogenesis. Tax expression transforms T cells in vitro and induces ATL-like disease in mice. Tax also induces a rough eye phenotype and increases hemocyte count in Drosophila melanogaster, indicative of transformation. Among multiple functions, Tax modulates the expression of the enhancer of zeste homolog 2 (EZH2), a methyltransferase of the Polycomb Repressive Complex 2 (PRC2), leading to H3K27me3-dependent reprogramming of around half of cellular genes. HBZ is a negative regulator of Tax-mediated viral transcription. HBZ effects on epigenetic signatures are underexplored. Here, we established an hbz transgenic fly model, and demonstrated that, unlike Tax, which induces NF-κB activation and enhanced PRC2 activity creating an activation loop, HBZ neither induces transformation nor NF-κB activation in vivo. However, overexpression of Tax or HBZ increases the PRC2 activity and both proteins directly interact with PRC2 complex core components. Importantly, overexpression of HBZ in tax transgenic flies prevents Tax-induced NF-κB or PRC2 activation and totally rescues Tax-induced transformation and senescence. Our results establish the in vivo antagonistic effect of HBZ on Tax-induced transformation and cellular effects. This study helps understanding long-term HTLV-1 persistence and cellular transformation and opens perspectives for new therapeutic strategies targeting the epigenetic machinery in ATL.

Ubiquitin-Related Modifier 1 (URM-1) Modulates Cx43 in Breast Cancer Cell Lines.

Gap-junction-forming connexins are exquisitely regulated by post-translational modifications (PTMs). In particular, the PTM of connexin 43 (Cx43), a tumor suppressor protein, regulates its turnover and activity. Here, we investigated the interaction of Cx43 with the ubiquitin-related modifier 1 (URM-1) protein and its impact on tumor progression in two breast cancer cell lines, highly metastatic triple-negative MDA-MB-231 and luminal breast cancer MCF-7 cell lines. To evaluate the subsequent modulation of Cx43 levels, URM-1 was downregulated in these cells. The transcriptional levels of epithelial-to-mesenchymal transition (EMT) markers and the metastatic phenotype were assessed. We demonstrated that Cx43 co-localizes and interacts with URM-1, and URMylated Cx43 was accentuated upon cellular stress. The significant upregulation of small ubiquitin-like modifier-1 (SUMO-1) was also observed. In cells with downregulated URM-1, Cx43 expression significantly decreased, and SUMOylation by SUMO-1 was affected. The concomitant expression of EMT markers increased, leading to increased proliferation, migration, and invasion potential. Inversely, the upregulation of URM-1 increased Cx43 expression and reversed EMT-induced processes, underpinning a role for this PTM in the observed phenotypes. This study proposes that the URMylation of Cx43 in breast cancer cells regulates its tumor suppression properties and contributes to breast cancer cell malignancy.

EAPB0503, an Imidazoquinoxaline Derivative Modulates SENP3/ARF Mediated SUMOylation, and Induces NPM1c Degradation in NPM1 Mutant AML.

Nucleophosmin-1 (NPM1) is a pleiotropic protein involved in numerous cellular processes. NPM1 shuttles between the nucleus and the cytoplasm, but exhibits a predominant nucleolar localization, where its fate and functions are exquisitely controlled by dynamic post-translational modifications (PTM). Sentrin/SUMO Specific Peptidase 3 (SENP3) and ARF are two nucleolar proteins involved in NPM1 PTMs. SENP3 antagonizes ARF-mediated NPM1 SUMOylation, to promote ribosomal biogenesis. In Acute Myeloid Leukemia (AML), NPM1 is frequently mutated, and exhibits an aberrant cytoplasmic localization (NPM1c). NPM1c mutations define a separate AML entity with good prognosis in some AML patients, rendering NPM1c as a potential therapeutic target. SENP3-mediated NPM1 de-SUMOylation induces resistance to therapy in NPM1c AML. Here, we demonstrate that the imidazoquinoxaline EAPB0503 prolongs the survival and results in selective reduction in the leukemia burden of NPM1c AML xenograft mice. Indeed, EAPB0503 selectively downregulates HDM2 expression and activates the p53 pathway in NPM1c expressing cells, resulting in apoptosis. Importantly, we unraveled that NPM1c expressing cells exhibit low basal levels of SUMOylation paralleled with high SENP3 and low ARF basal levels. EAPB0503 reverted these molecular players by inducing NPM1c SUMOylation and ubiquitylation, leading to its proteasomal degradation. EAPB0503-induced NPM1c SUMOylation is concurrent with SENP3 downregulation and ARF upregulation in NPM1c expressing cells. Collectively, these results provide a strong rationale for testing therapies modulating NPM1c post-translational modifications in the management of NPM1c AML.

A Novel Approach for Tuberous Breast Correction Using Power-Assisted Liposuction, Loops, and Lipofilling (PALLL).

BACKGROUND: Autologous fat grafting has recently gained popularity in breast and reconstructive procedures. OBJECTIVES: The aim of this paper was to describe a tricomposite tuberous breast reconstruction that comprises matrix dissociation through extensive tunnelization, tissue recruitment with loops, and autologous fat transfer. This approach, called "matrix modeling," was implemented by the power-assisted liposuction, loops, and lipofilling (PALLL) technique as a method to expand the lower pole, reshape the breast, and increase breast volume. METHODS: Between 2014 and 2020, a total of 47 patients underwent tuberous breast correction by combined lipofilling and the use of breast loops. The patient population included patients with unilateral or bilateral tuberous breasts of any stage. Patients who were active smokers, lean, or who desired large breasts were excluded from the study. RESULTS: Of the 47 patients (mean age, 26 years), 31 had bilateral malformations. The mean recruited flap volume was 212 mL. A single session (mean transfer volume, 163 mL) was required in 34 cases (72%). A second session (mean transfer volume, 182 mL) was necessary in the remaining 28% of cases. Patients were very satisfied in 93% of cases and satisfied in 7% of cases. One infection was observed. The mean operative time was 67 minutes. Imaging performed preoperatively and 1 year postoperatively did not reveal any anomalies other than oil cysts (4%). CONCLUSIONS: Tricomposite breast reconstruction by PALLL is a novel, simple, safe, and alternative technique for tuberous breast correction by remodeling the matrix. The aesthetic outcome is natural, implant free, and long lasting.

Scarless Composite Breast Reconstruction Utilizing an Advancement Skin Flap, Loops, and Lipofilling.

BACKGROUND: Autologous fat grafting has gained popularity in breast reconstructive surgery. To further increase the breast volume and provide a reliable breast shape, a skin flap can be advanced from the upper abdomen and lateral thorax to the breast. OBJECTIVES: The aim of this study was to propose a method of breast reconstruction utilizing the principles of power-assisted liposuction and lipofilling (PALL) for breast matrix dissociation applied through infiltration, tunnelization, extensive undermining and lipofilling, in combination with loops (PALLL) to recruit a vascularized flap to reshape the breast. METHODS: A prospective study was performed from January 2014 to January 2019. Demographic data, surgical procedure information (including volumes of the recruited advancement flap and lipofilling, and stages of lipofilling), and complication data were collected. Patient-reported outcomes, including satisfaction and well-being, were measured by a questionnaire. RESULTS: In total, 37 women (41 breasts) underwent breast reconstruction by PALLL with an average follow-up of 26 months. The mean age of the patients was 54 years, and their mean BMI was 29 kg/m2. The mean recruited flap volume was 197 mL, and the mean lipofilling volumes were 153 mL for the first session, 190 mL for the second session, and 110 mL for the third session. Nine patients needed 3 sessions, 27 patients 2 sessions, and 1 patient only 1 session. Overall, 94% of patients were satisfied with their breast shape. All patients reported sensitive breasts. There were minimal complications. CONCLUSIONS: Breast reconstruction with PALLL is a minimally invasive alternative to reconstructing and reshaping sensate breasts in which a vascularized skin flap recruited by loops from breast surroundings is combined with fat grafting. This approach provides long-term shape stability with minimal scarring and low complication rates.

A Pin1/PML/P53 axis activated by retinoic acid in NPM-1c acute myeloid leukemia.

Retinoic acid (RA) was proposed to increase survival of chemotherapy- treated patients with nucleophosmin-1 (NPM-1c)-mutated acute myeloid leukemia. We reported that, ex vivo, RA triggers NPM-1c degradation, P53 activation and growth arrest. PML organizes domains that control senescence or proteolysis. Here, we demonstrate that PML is required to initiate RA-driven NPM-1c degradation, P53 activation and cell death. Mechanistically, RA enhances PML basal expression through inhibition of activated Pin1, prior to NPM-1c degradation. Such PML induction drives P53 activation, favoring blast response to chemotherapy or arsenic in vivo. This RA/PML/P53 cascade could mechanistically explain RA-facilitated chemotherapy response in patients with NPM-1c mutated acute myeloid leukemia.

Loss of interleukin-10 activates innate immunity to eradicate adult T-cell leukemia-initiating cells.

Adult T cell leukemia/lymphoma (ATL) is associated to chronic human T cell leukemia virus type 1 (HTLV-1) infection and carries a poor prognosis. Arsenic trioxide (AS) and interferon-alpha (IFNα) together selectively trigger Tax viral oncoprotein degradation and cure Tax-driven murine ATL. AS/IFNα/zidovudine treatment achieves a high response rate in patients with chronic ATL. Interleukin 10 (IL-10) is an immuno-suppressive cytokine whose expression is activated by Tax. Here we show that, in ATL, AS/IFNα-induced abrogation of leukemia initiating cell activity requires IL-10 expression shutoff. Loss of IL-10 secretion drives production of inflammatory cytokines by the microenvironment, followed by innate immunity-mediated clearance of Taxdriven leukemic cells. Accordingly, anti-IL-10 monoclonal antibodies significantly increased the efficiency of AS/IFNα therapy. These results emphasize the sequential targeting of malignant ATL cells and their immune microenvironment in leukemia initiating cell (LIC) eradication and provide a strong rational to test AS/IFNα/anti-IL10 combination in ATL.

Adult T-Cell Leukemia: a Comprehensive Overview on Current and Promising Treatment Modalities.

PURPOSE OF THE REVIEW: Adult T-cell leukemia (ATL) is an aggressive chemo-resistant malignancy secondary to HTLV-1 retrovirus. Prognosis of ATL remains dismal. Herein, we emphasized on the current ATL treatment modalities and their drawbacks, and opened up on promising targeted therapies with special focus on the HTLV-1 regulatory proteins Tax and HBZ. RECENT FINDINGS: Indolent ATL and a fraction of acute ATL exhibit long-term survival following antiviral treatment with zidovudine and interferon-alpha. Monoclonal antibodies such as mogamulizumab improved response rates, but with little effect on survival. Allogeneic hematopoietic cell transplantation results in long-term survival in one third of transplanted patients, alas only few patients are transplanted. Salvage therapy with lenalidomide in relapsed/refractory patients leads to prolonged survival in some of them. ATL remains an unmet medical need. Targeted therapies focusing on the HTLV-1 viral replication and/or viral regulatory proteins, as well as on the host antiviral immunity, represent a promising approach for the treatment of ATL.

No-Scar Breast Reduction Utilizing Power-Assisted Liposuction Mammaplasty, Loops, and Lipofilling.

BACKGROUND: In continued interest to develop and refine minimally invasive procedures, recent publications reported a scarless approach in breast lifting. OBJECTIVES: The authors sought to describe a power-assisted lipomodeling technique combined with surgical loops to achieve breast reduction and reshaping with minimal scars. METHODS: Between 2014 and 2018, 94 patients underwent breast reduction by combined liposuction and loops. Following infiltration of the breasts, liposuction of the outer quadrants and the lower pole was achieved to reduce the breast footprint and the lateral and inferior heaviness of the breast. After multiaxial multiplanar tunnelization, 3 types of loops were taken around the breast to suspend and elevate the breast skin envelope and parenchyma. Each loop was guided through a 3-mm, 3-hole cannula passed through skin stab incisions. The first loop was designed to reduce the breast footprint and enhance the breast projection, whereas the second loop was designed to achieve breast conus remodeling. The third loop was passed circumferentially around the areola and then cephalad along the breast axis and pulled until the desired nipple-areola complex elevation was reached. Each loop was pulled to achieve the desired breast projection and shape. RESULTS: The authors achieved breast reduction with a mean nipple elevation of 7.3 cm, and 88% of patients were satisfied with their breast shape. The total complication rate was 1%, including mild cellulitis in 1 breast, treated efficiently with oral antibiotics. CONCLUSIONS: The proposed technique is a novel, simple, and safe alternative to achieve breast reduction and reshaping without a scar.

Improving the Female Silhouette and Gluteal Projection: An Anatomy-Based, Safe, and Harmonious Approach Through Liposuction, Suspension Loops, and Moderate Lipofilling.

BACKGROUND: Liposuction is the main technique to improve body contour, emphasize appealing curves, and highlight one's muscular definition. The number of procedures in which the harvested fat is utilized for gluteal augmentation has greatly increased. OBJECTIVES: The authors aim to demonstrate their technique in order to obtain a sculpted harmonious body through a safe procedure, as well as review their 101 consecutive cases between 2014 and 2018. METHODS: Anatomical guidelines and preoperative markings were provided to guide the 3-step procedure: zones of maximal and mild liposuction, barbed wire suspension, and moderate fat grafting. Novel concepts are introduced as the anterior body diagonal, posterior body diagonal as well as other specific axes the pubic unit, and a vertical ratio for the buttock, which are the basic foundations for sculpting the female body into a pleasing hourglass shape with a well projected buttock. Recommendations for location of sacral diamond, sacral dimples, and the maximally projected point of the buttock are given. The authors explain their philosophy through 4 principles: knowledge of anatomy, the relationship between specific body areas and surrounding zones, a balanced gluteal augmentation is not achieved through large volume fat grafting alone, and grafting in the subcutaneous layer. RESULTS: A total of 101 patients were treated following the described technique and examples are shown. The complication rate was low. No serious adverse effects were recorded apart from 1 ruptured suspension loop. CONCLUSIONS: The described anatomy-based approach, including liposuction, suspension loops, and fat grafting, is a novel and safe technique leading to a desirable, long-lasting outcome.

Psychometric evaluation of the Lebanese Arabic version of the Dental Fear Survey: a cross-sectional study.

BACKGROUND: Dental fear is a prevalent problem that can lead to poor dental health. The Kleinknecht's Dental Fear Survey (DFS) is one of the used scales to assess dental fear. The present study aims to evaluate the psychometric properties of the Lebanese Arabic version of the DFS (DFS-A) and to determine the optimal cut-off to identify dental fear as well as the correlates of dental fear in a group of Lebanese adults dental patients. METHODS: A cross-sectional study was conducted among a group of 442 dental patients (18-65 years) recruited at 29 dental clinics from March to June 2019. Patients completed a questionnaire including questions about demographic characteristics, previous bad dental experience, trauma's experience period, the sensation of nausea during dental treatment, the DFS-A scale, the Lebanese Arabic version of the Modified Dental Anxiety Scale (MDAS-A), and a general question about dental fear. RESULTS: DFS-A revealed evidence of adequate psychometric properties. DFS-A scale demonstrated high internal consistency (cronbach's alpha = 0.93). Test-retest reliability assessment demonstrated strong reproducibility of the DFS-A scale score (ICC = 0.92 with 95% CI (0.83-0.96), p value < 0.0001 (N = 30). Confirmatory factor analysis revealed a three-factor structure of the DFS-A reflecting fear associated with specific dental stimuli and procedures, patterns of dental avoidance and anticipatory anxiety, and physiologic arousal during dental treatment. A significant correlation was found between DFS-A and the MDAS-A indicating a good convergent validity. The optimal cut-off point to identify patients with and without dental fear is 41. Considering this cut-off score, the prevalence of dental fear in our sample was reported at 33.8%. Multivariable analysis showed that having previous scary and painful dental experiences, a sensation of nausea during treatment, and having dental anxiety were identified as predictors of dental fear. CONCLUSION: The adapted Arabic version of the DFS (DFS-A) is a valid tool to evaluate dental fear among Lebanese adult patients.

Assessment of dental anxiety and dental phobia among adults in Lebanon.

BACKGROUND: Dental anxiety continues to be a widespread problem affecting adult populations. The primary aim of our study was to evaluate the psychometric properties of the Lebanese Arabic version of the Modified Dental Anxiety Scale (MDAS-A) and to identify the optimal cut-off for assessing dental anxiety and dental phobia among adults in Lebanon. In addition, we sought to assess dental anxiety and phobia as well as their correlates among Lebanese adult patients. METHODS: A cross-sectional study was carried out on a sample of 451 dental adult patients aged between 18 and 65 years old. Information about demographic characteristics, previous bad dental experience, trauma's experience period, perception of a periodontal problem, sensation of nausea during dental treatment, the MDAS-A scale, and the Visual Analogue Scale for anxiety (VAS-A) were collected. RESULTS: MDAS-A exhibited evidence of adequate psychometric properties. The optimal cut-off was 12 for dental anxiety and 14 for dental phobia. Out of the total sample, 31.5% suffered from dental anxiety while 22.4% had a dental phobia. Multivariable analysis showed that the odds of dental anxiety and phobia were higher among females compared to males. Also, patients suffering from periodontal problem perceptions, bad dental experiences during childhood and adolescence, and the sensation of nausea during dental treatment were at a higher risk of developing dental anxiety and phobia compared to their counterparts. However, a higher level of education was found to be a protective factor against dental phobia among Lebanese adult patients. CONCLUSION: The MDAS-A scale is a suitable tool for the routine assessment of dental anxiety and phobia among Lebanese adult patients. Identifying patients with dental anxiety at the earliest opportunity is of utmost importance for delivering successful dental care.

A proteomic analysis unravels novel CORVET and HOPS proteins involved in Toxoplasma gondii secretory organelles biogenesis.

Apicomplexans use the endolysosomal system for the biogenesis of their secretory organelles, namely, micronemes, rhoptries, and dense granules. In Toxoplasma gondii, our previous in silico search identified the HOPS tethering but not the CORVET complex and demonstrated a role of Vps11 (a common component for both complexes) in its secretory organelle biogenesis. Herein, we performed Vps11-GFP-Trap pull-down assays and identified by proteomic analysis, not only the CORVET-specific subunit Vps8 but also a BEACH domain-containing protein (BDCP) conserved in eukaryotes. We show that knocking-down Vps8 affects targeting of dense granule proteins, transport of rhoptry proteins, and the localization of the cathepsin L protease vacuolar compartment marker. Only a subset of micronemal proteins are affected by the absence of Vps8, shedding light on at least two trafficking pathways involved in microneme maturation. Knocking-down BDCP revealed a restricted and particular role of this protein in rhoptry and vacuolar compartment biogenesis. Moreover, depletion of BDCP or Vps8 abolishes parasite virulence in vivo. This study identified BDCP as a novel CORVET/HOPS-associated protein, playing specific roles and acting in concert during secretory organelle biogenesis, an essential process for host cell infection. Our results open the hypothesis for a role of BDCP in the vesicular trafficking towards lysosome-related organelles in mammals and yeast.

Fatal Visceral Leishmaniasis Caused by Leishmania infantum, Lebanon.

Visceral leishmaniasis, a fatal disease if not treated, is caused by Leishmania parasites. This disease might be overlooked in the Middle East because of limited awareness and low incidence. We report 5 patients who died of visceral leishmaniasis in Lebanon and make recommendations to improve faster diagnosis and treatment.

Toxoplasma gondii autophagy-related protein ATG9 is crucial for the survival of parasites in their host.

Autophagy is a conserved, life-promoting, catabolic process involved in the recycling of nonessential cellular components in response to stress. The parasite Toxoplasma gondii is an early-diverging eukaryote in which part of the autophagy machinery is not exclusively involved in a catabolic process but instead has been repurposed for an original function in organelle inheritance during cell division. This function, depending essentially on protein TgATG8 and its membrane conjugation system, is crucial for parasite survival and prevented an in depth study of autophagy in the mutants generated so far in Toxoplasma. Thus, in order to decipher the primary function of canonical autophagy in the parasites, we generated a cell line deficient for TgATG9, a protein thought to be involved in the early steps of the autophagy process. Although the protein proved to be dispensable for the development of these obligate intracellular parasites in vitro, the absence of TgATG9 led to a reduced ability to sustain prolonged extracellular stress. Importantly, depletion of the protein significantly reduced parasites survival in macrophages and markedly attenuated their virulence in mice. Altogether, this shows TgATG9 is important for the fate of Toxoplasma in immune cells and contributes to the overall virulence of the parasite, possibly through an involvement in a canonical autophagy pathway.

Imidazoquinoxaline derivative EAPB0503: A promising drug targeting mutant nucleophosmin 1 in acute myeloid leukemia.

BACKGROUND: Nucleophosmin 1 (NPM1) is a nucleocytoplasmic shuttling protein mainly localized in the nucleolus. NPM1 is frequently mutated in acute myeloid leukemia (AML). NPM1c oligomerizes with wild-type nucleophosmin 1 (wt-NPM1), and this leads to its continuous cytoplasmic delocalization and contributes to leukemogenesis. Recent studies have shown that Cytoplasmic NPM1 (NPM1c) degradation leads to growth arrest and apoptosis of NPM1c AML cells and corrects wt-NPM1 normal nucleolar localization. METHODS: AML cells expressing wt-NPM1 or NPM1c or transfected with wt-NPM1 or NPM1c as well as wt-NPM1 and NPM1c AML xenograft mice were used. Cell growth was assessed with trypan blue or a CellTiter 96 proliferation kit. The cell cycle was studied with a propidium iodide (PI) assay. Caspase-mediated intrinsic apoptosis was assessed with annexin V/PI, the mitochondrial membrane potential, and poly(adenosine diphosphate ribose) polymerase cleavage. The expression of NPM1, p53, phosphorylated p53, and p21 was analyzed via immunoblotting. Localization was performed with confocal microscopy. The leukemia burden was evaluated by flow cytometry with an anti-human CD45 antibody. RESULTS: The imidazoquinoxaline 1-(3-methoxyphenyl)-N-methylimidazo[1,2-a]quinoxalin-4-amine (EAPB0503) induced selective proteasome-mediated degradation of NPM1c, restored wt-NPM1 nucleolar localization in NPM1c AML cells, and thus yielded selective growth arrest and apoptosis. Introducing NPM1c to cells normally harboring wt-NPM1 sensitized them to EAPB0503 and led to their growth arrest. Moreover, EAPB0503 selectively reduced the leukemia burden in NPM1c AML xenograft mice. CONCLUSIONS: These findings further reinforce the idea of targeting the NPM1c oncoprotein to eradicate leukemic cells and warrant a broader preclinical evaluation and then a clinical evaluation of this promising drug. Cancer 2017;123:1662-1673. © 2017 American Cancer Society.

ATL response to arsenic/interferon therapy is triggered by SUMO/PML/RNF4-dependent Tax degradation.

The human T-cell lymphotropic virus type I (HTLV-1) Tax transactivator initiates transformation in adult T-cell leukemia/lymphoma (ATL), a highly aggressive chemotherapy-resistant malignancy. The arsenic/interferon combination, which triggers degradation of the Tax oncoprotein, selectively induces apoptosis of ATL cell lines and has significant clinical activity in Tax-driven murine ATL or human patients. However, the role of Tax loss in ATL response is disputed, and the molecular mechanisms driving degradation remain elusive. Here we demonstrate that ATL-derived or HTLV-1-transformed cells are dependent on continuous Tax expression, suggesting that Tax degradation underlies clinical responses to the arsenic/interferon combination. The latter enforces promyelocytic leukemia protein (PML) nuclear body (NB) formation and partner protein recruitment. In arsenic/interferon-treated HTLV-1 transformed or ATL cells, Tax is recruited onto NBs and undergoes PML-dependent hyper-sumoylation by small ubiquitin-like modifier (SUMO)2/3 but not SUMO1, ubiquitination by RNF4, and proteasome-dependent degradation. Thus, the arsenic/interferon combination clears ATL through degradation of its Tax driver, and this regimen could have broader therapeutic value by promoting degradation of other pathogenic sumoylated proteins.

Retinoic acid and arsenic trioxide trigger degradation of mutated NPM1, resulting in apoptosis of AML cells.

Nucleophosmin-1 (NPM1) is the most frequently mutated gene in acute myeloid leukemia (AML). Addition of retinoic acid (RA) to chemotherapy was proposed to improve survival of some of these patients. Here, we found that RA or arsenic trioxide synergistically induce proteasomal degradation of mutant NPM1 in AML cell lines or primary samples, leading to differentiation and apoptosis. NPM1 mutation not only delocalizes NPM1 from the nucleolus, but it also disorganizes promyelocytic leukemia (PML) nuclear bodies. Combined RA/arsenic treatment significantly reduced bone marrow blasts in 3 patients and restored the subnuclear localization of both NPM1 and PML. These findings could explain the proposed benefit of adding RA to chemotherapy in NPM1 mutant AMLs, and warrant a broader clinical evaluation of regimen comprising a RA/arsenic combination.

The conserved apicomplexan Aurora kinase TgArk3 is involved in endodyogeny, duplication rate and parasite virulence.

Aurora kinases are eukaryotic serine/threonine protein kinases that regulate key events associated with chromatin condensation, centrosome and spindle function and cytokinesis. Elucidating the roles of Aurora kinases in apicomplexan parasites is crucial to understand the cell cycle control during Plasmodium schizogony or Toxoplasma endodyogeny. Here, we report on the localization of two previously uncharacterized Toxoplasma Aurora-related kinases (Ark2 and Ark3) in tachyzoites and of the uncharacterized Ark3 orthologue in Plasmodium falciparum erythrocytic stages. In Toxoplasma gondii, we show that TgArk2 and TgArk3 concentrate at specific sub-cellular structures linked to parasite division: the mitotic spindle and intranuclear mitotic structures (TgArk2), and the outer core of the centrosome and the budding daughter cells cytoskeleton (TgArk3). By tagging the endogenous PfArk3 gene with the green fluorescent protein in live parasites, we show that PfArk3 protein expression peaks late in schizogony and localizes at the periphery of budding schizonts. Disruption of the TgArk2 gene reveals no essential function for tachyzoite propagation in vitro, which is surprising giving that the P. falciparum and P. berghei orthologues are essential for erythrocyte schizogony. In contrast, knock-down of TgArk3 protein results in pronounced defects in parasite division and a major growth deficiency. TgArk3-depleted parasites display several defects, such as reduced parasite growth rate, delayed egress and parasite duplication, defect in rosette formation, reduced parasite size and invasion efficiency and lack of virulence in mice. Our study provides new insights into cell cycle control in Toxoplasma and malaria parasites and highlights Aurora kinase 3 as potential drug target.