Polo-like kinase 1 regulates immune synapse assembly and cytotoxic T cell function by driving microtubule dynamics

Elimination of virally infected or tumoral cells is mediated by cytotoxic T cells (CTL). Upon antigen recognition, CTLs assemble a specialized signaling and secretory domain at the interface with their target, the immune synapse (IS). During IS formation, CTLs acquire a transient polarity, marked by re-orientation of the centrosome and microtubule cytoskeleton toward the IS, thus directing the transport and delivery of the lytic granules to the target cell. Based on the implication that the kinase Aurora A has a role in CTL function, we hypothesized that its substrate, the mitotic regulator Polo-like kinase 1 (PLK1), might participate in CTL IS assembly. We demonstrate that PLK1 is phosphorylated upon TCR triggering and polarizes to the IS. PLK1 silencing or inhibition results in impaired IS assembly and function, as witnessed by defective synaptic accumulation of T cell receptors (TCRs), as well as compromised centrosome and lytic granule polarization to the IS, resulting in impaired target cell killing. This function is achieved by coupling early signaling to microtubule dynamics, a function pivotal for CTL-mediated cytotoxicity. These results identify PLK1 as a new player in CTL IS assembly and function.

Emerging roles of SARS-CoV-2 Spike-ACE2 in immune evasion and pathogenesis

The COVID-19 pandemic, caused by SARS-CoV-2, has caused an estimated 5 billion infections and 20 million deaths by respiratory failure. In addition to the respiratory disease, SARS-CoV-2 infection has been associated with many extrapulmonary complications not easily explainable by the respiratory infection. A recent study showed that the SARS-CoV-2 spike protein, which mediates cell entry by binding to the angiotensin-converting enzyme 2 (ACE2) receptor, signals through ACE2 to change host cell behavior. In CD8⁺ T cells, spike-dependent ACE2-mediated signaling suppresses immunological synapse (IS) formation and impairs their killing ability, leading to immune escape of virus-infected cells. In this opinion article, we discuss the consequences of ACE2 signaling on the immune response and propose that it contributes to the extrapulmonary manifestations of COVID-19.

SARS-CoV-2 Spike protein suppresses CTL-mediated killing by inhibiting immune synapse assembly

CTL-mediated killing of virally infected or malignant cells is orchestrated at the immune synapse (IS). We hypothesized that SARS-CoV-2 may target lytic IS assembly to escape elimination. We show that human CD8+ T cells upregulate the expression of ACE2, the Spike receptor, during differentiation to CTLs. CTL preincubation with the Wuhan or Omicron Spike variants inhibits IS assembly and function, as shown by defective synaptic accumulation of TCRs and tyrosine phosphoproteins as well as defective centrosome and lytic granule polarization to the IS, resulting in impaired target cell killing and cytokine production. These defects were reversed by anti-Spike antibodies interfering with ACE2 binding and reproduced by ACE2 engagement by angiotensin II or anti-ACE2 antibodies, but not by the ACE2 product Ang (1-7). IS defects were also observed ex vivo in CTLs from COVID-19 patients. These results highlight a new strategy of immune evasion by SARS-CoV-2 based on the Spike-dependent, ACE2-mediated targeting of the lytic IS to prevent elimination of infected cells.

IFT20: An Eclectic Regulator of Cellular Processes beyond Intraflagellar Transport

Initially discovered as the smallest component of the intraflagellar transport (IFT) system, the IFT20 protein has been found to be implicated in several unconventional mechanisms beyond its essential role in the assembly and maintenance of the primary cilium. IFT20 is now considered a key player not only in ciliogenesis but also in vesicular trafficking of membrane receptors and signaling proteins. Moreover, its ability to associate with a wide array of interacting partners in a cell-type specific manner has expanded the function of IFT20 to the regulation of intracellular degradative and secretory pathways. In this review, we will present an overview of the multifaceted role of IFT20 in both ciliated and non-ciliated cells.

A CVID-associated variant in the ciliogenesis protein CCDC28B disrupts immune synapse assembly

Ciliogenesis proteins orchestrate vesicular trafficking pathways that regulate immune synapse (IS) assembly in the non-ciliated T-cells. We hypothesized that ciliogenesis-related genes might be disease candidates for common variable immunodeficiency with impaired T-cell function (T-CVID). We identified a heterozygous, predicted pathogenic variant in the ciliogenesis protein CCDC28B present with increased frequency in a large CVID cohort. We show that CCDC28B participates in IS assembly by regulating polarized T-cell antigen receptor (TCR) recycling. This involves the CCDC28B-dependent, FAM21-mediated recruitment of the actin regulator WASH to retromer at early endosomes to promote actin polymerization. The CVID-associated CCDC28B^R25W variant failed to interact with FAM21, leading to impaired synaptic TCR recycling. CVID T cells carrying the ccdc28b 211 C > T allele displayed IS defects mapping to this pathway that were corrected by overexpression of the wild-type allele. These results identify a new disease gene in T-CVID and pinpoint CCDC28B as a new player in IS assembly.

The Bardet-Biedl syndrome complex component BBS1 controls T cell polarity during immune synapse assembly

Components of the intraflagellar transport (IFT) system that regulates the assembly of the primary cilium are co-opted by the non-ciliated T cell to orchestrate polarized endosome recycling and to sustain signaling during immune synapse formation. Here, we investigated the potential role of Bardet-Biedl syndrome 1 protein (BBS1), an essential core component of the BBS complex that cooperates with the IFT system in ciliary protein trafficking, in the assembly of the T cell synapse. We demonstrated that BBS1 allows for centrosome polarization towards the immune synapse. This function is achieved through the clearance of centrosomal F-actin and its positive regulator WASH1 (also known as WASHC1), a process that we demonstrated to be dependent on the proteasome. We show that BBS1 regulates this process by coupling the 19S proteasome regulatory subunit to the microtubule motor dynein for its transport to the centrosome. Our data identify the ciliopathy-related protein BBS1 as a new player in T cell synapse assembly that functions upstream of the IFT system to set the stage for polarized vesicular trafficking and sustained signaling. This article has an associated First Person interview with the first author of the paper.

The Intraflagellar Transport Protein IFT20 Recruits ATG16L1 to Early Endosomes to Promote Autophagosome Formation in T Cells

Lymphocyte homeostasis, activation and differentiation crucially rely on basal autophagy. The fine-tuning of this process depends on autophagy-related (ATG) proteins and their interaction with the trafficking machinery that orchestrates the membrane rearrangements leading to autophagosome biogenesis. The underlying mechanisms are as yet not fully understood. The intraflagellar transport (IFT) system, known for its role in cargo transport along the axonemal microtubules of the primary cilium, has emerged as a regulator of autophagy in ciliated cells. Growing evidence indicates that ciliogenesis proteins participate in cilia-independent processes, including autophagy, in the non-ciliated T cell. Here we investigate the mechanism by which IFT20, an integral component of the IFT system, regulates basal T cell autophagy. We show that IFT20 interacts with the core autophagy protein ATG16L1 and that its CC domain is essential for its pro-autophagic activity. We demonstrate that IFT20 is required for the association of ATG16L1 with the Golgi complex and early endosomes, both of which have been identified as membrane sources for phagophore elongation. This involves the ability of IFT20 to interact with proteins that are resident at these subcellular localizations, namely the golgin GMAP210 at the Golgi apparatus and Rab5 at early endosomes. GMAP210 depletion, while leading to a dispersion of ATG16L1 from the Golgi, did not affect basal autophagy. Conversely, IFT20 was found to recruit ATG16L1 to early endosomes tagged for autophagosome formation by the BECLIN 1/VPS34/Rab5 complex, which resulted in the local accumulation of LC3. Hence IFT20 participates in autophagosome biogenesis under basal conditions by regulating the localization of ATG16L1 at early endosomes to promote autophagosome biogenesis. These data identify IFT20 as a new regulator of an early step of basal autophagy in T cells.

Regulation of Selective B Cell Autophagy by the Pro-oxidant Adaptor p66SHC

p66SHC is a pro-oxidant member of the SHC family of protein adaptors that acts as a negative regulator of cell survival. In lymphocytes p66SHC exploits both its adaptor and its reactive oxygen species (ROS)-elevating function to antagonize mitogenic and survival signaling and promote apoptosis. As a result, p66SHC deficiency leads to the abnormal expansion of peripheral T and B cells and lupus-like autoimmunity. Additionally, a defect in p66SHC expression is a hallmark of B cell chronic lymphocytic leukemia, where it contributes to the accumulation of long-lived neoplastic cells. We have recently provided evidence that p66SHC exerts a further layer of control on B cell homeostasis by acting as a new mitochondrial LC3-II receptor to promote the autophagic demise of dysfunctional mitochondria. Here we discuss this finding in the context of the autophagic control of B cell homeostasis, development, and differentiation in health and disease.

Orchestration of Immunological Synapse Assembly by Vesicular Trafficking

Ligation of the T-cell antigen receptor (TCR) by cognate peptide bound to the Major Histocompatibility Complex on the surface of an antigen-presenting cell (APC) leads to the spatial reorganization of the TCR and accessory receptors to form a specialized area of intimate contact between T cell and APC, known as the immunological synapse (IS), where signals are deciphered, coordinated, and integrated to promote T cell activation. With the discovery that an endosomal TCR pool contributes to IS assembly and function by undergoing polarized recycling to the IS, recent years have witnessed a shift from a plasma membrane-centric view of the IS to the vesicular trafficking events that occur at this location following the TCR-dependent translocation of the centrosome toward the synaptic membrane. Here we will summarize our current understanding of the trafficking pathways that are responsible for the steady delivery of endosomal TCRs, kinases, and adapters to the IS to sustain signaling, as well as of the endocytic pathways responsible for signal termination. We will also discuss recent evidence highlighting a role for endosomes in sustaining TCR signaling after its internalization at the IS and identifying the IS as a site of formation and release of extracellular vesicles that allow for transcellular communication with the APC.

The intraflagellar transport protein IFT20 controls lysosome biogenesis by regulating the post-Golgi transport of acid hydrolases

The assembly and function of the primary cilium depends on multimolecular intraflagellar transport (IFT) complexes that shuttle their cargo along the axonemal microtubules through their interaction with molecular motors. The IFT system has been moreover recently implicated in a reciprocal interplay between autophagy and ciliogenesis. We have previously reported that IFT20 and other components of the IFT complexes participate in the assembly of the immune synapse in the non-ciliated T cell, suggesting that other cellular processes regulated by the IFT system in ciliated cells, including autophagy, may be shared by cells lacking a cilium. Starting from the observation of a defect in autophagic clearance and an accumulation of lipid droplets in IFT20-deficient T cells, we show that IFT20 is required for lysosome biogenesis and function by controlling the lysosomal targeting of acid hydrolases. This function involves its ability to regulate the retrograde traffic of the cation-independent mannose-6-phosphate receptor (CI-MPR) to the trans-Golgi network, which is achieved by coupling recycling CI-MPRs to the microtubule motor dynein. Consistent with the lysosomal defect, an upregulation of the TFEB-dependent expression of the lysosomal gene network can be observed in IFT20-deficient cells, which is associated with defective tonic T-cell antigen receptor signaling and mTOR activity. We additionally show that the lysosome-related function of IFT20 extends to non-ciliated cells other than T cells, as well as to ciliated cells. Our findings provide the first evidence that a component of the IFT system that controls ciliogenesis is implicated in the biogenesis of lysosomes.

The pro-oxidant adaptor p66SHC promotes B cell mitophagy by disrupting mitochondrial integrity and recruiting LC3-II

Macroautophagy/autophagy has emerged as a central process in lymphocyte homeostasis, activation and differentiation. Based on our finding that the p66 isoform of SHC1 (p66SHC) pro-apoptotic ROS-elevating SHC family adaptor inhibits MTOR signaling in these cells, here we investigated the role of p66SHC in B-cell autophagy. We show that p66SHC disrupts mitochondrial function through its CYCS (cytochrome c, somatic) binding domain, thereby impairing ATP production, which results in AMPK activation and enhanced autophagic flux. While p66SHC binding to CYCS is sufficient for triggering apoptosis, p66SHC-mediated autophagy additionally depends on its ability to interact with membrane-associated LC3-II through a specific binding motif within its N terminus. Importantly, p66SHC also has an impact on mitochondria homeostasis by inducing mitochondrial depolarization, protein ubiquitination at the outer mitochondrial membrane, and local recruitment of active AMPK. These events initiate mitophagy, whose full execution relies on the role of p66SHC as an LC3-II receptor which brings phagophore membranes to mitochondria. Importantly, p66SHC also promotes hypoxia-induced mitophagy in B cells. Moreover, p66SHC deficiency enhances B cell differentiation to plasma cells, which is controlled by intracellular ROS levels and the hypoxic germinal center environment. The results identify mitochondrial p66SHC as a novel regulator of autophagy and mitophagy in B cells and implicate p66SHC-mediated coordination of autophagy and apoptosis in B cell survival and differentiation. Abbreviations: ACTB: actin beta; AMPK: AMP-activated protein kinase; ATP: adenosine triphosphate; ATG: autophagy-related; CYCS: cytochrome c, somatic; CLQ: chloroquine; COX: cyclooxygenase; CTR: control; GFP: green fluorescent protein; HIFIA/Hif alpha: hypoxia inducible factor 1 subunit alpha; IMS: intermembrane space; LIR: LC3 interacting region; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MTOR/mTOR: mechanistic target of rapamycin kinase; OA: oligomycin and antimycin A; OMM: outer mitochondrial membrane; PHB: prohibitin; PBS: phosphate-buffered saline; PINK1: PTEN induced putative kinase 1; RFP: red fluorescent protein; ROS: reactive oxygen species; SHC: src Homology 2 domain-containing transforming protein; TMRM: tetramethylrhodamine, methyl ester; TOMM: translocase of outer mitochondrial membrane; ULK1: unc-51 like autophagy activating kinase 1; WT: wild-type.

Compartmentalized Cyclic AMP Production by the Bordetella pertussis and Bacillus anthracis Adenylate Cyclase Toxins Differentially Affects the Immune Synapse in T Lymphocytes

A central feature of the immune synapse (IS) is the tight compartmentalization of membrane receptors and signaling mediators that is functional for its ability to coordinate T cell activation. Second messengers centrally implicated in this process, such as Ca²⁺ and diacyl glycerol, also undergo compartmentalization at the IS. Current evidence suggests a more complex scenario for cyclic AMP (cAMP), which acts both as positive and as negative regulator of T-cell antigen receptor (TCR) signaling and which, as such, must be subjected to a tight spatiotemporal control to allow for signaling at the IS. Here, we have used two bacterial adenylate cyclase toxins that produce cAMP at different subcellular localizations as the result of their distinct routes of cell invasion, namely Bordetella pertussis CyaA and Bacillus anthracis edema toxin (ET), to address the ability of the T cell to confine cAMP to the site of production and to address the impact of compartmentalized cAMP production on IS assembly and function. We show that CyaA, which produces cAMP close to the synaptic membrane, affects IS stability by modulating not only the distribution of LFA-1 and its partners talin and L-plastin, as previously partly reported but also by promoting the sustained synaptic accumulation of the A-kinase adaptor protein ezrin and protein kinase A while suppressing the β-arrestin-mediated recruitment of phosphodiesterase 4B. These effects are dependent on the catalytic activity of the toxin and can be reproduced by treatment with a non-hydrolyzable cAMP analog. Remarkably, none of these effects are elicited by ET, which produces cAMP at a perinuclear localization, despite its ability to suppress TCR signaling and T cell activation through its cAMP-elevating activity. These results show that the IS responds solely to local elevations of cAMP and provide evidence that potent compartmentalization mechanisms are operational in T cells to contain cAMP close to the site of production, even when produced at supraphysiological levels.

The T cell IFT20 interactome reveals new players in immune synapse assembly

Sustained signalling at the immune synapse (IS) requires the synaptic delivery of recycling endosome-associated T cell antigen receptors (TCRs). IFT20, a component of the intraflagellar transport system, controls TCR recycling to the IS as a complex with IFT57 and IFT88. Here, we used quantitative mass spectrometry to identify additional interaction partners of IFT20 in Jurkat T cells. In addition to IFT57 and IFT88, the analysis revealed new binding partners, including IFT54 (also known as TRAF3IP1), GMAP-210 (also known as TRIP11), Arp2/3 complex subunit-3 (ARPC3), COP9 signalosome subunit-1 (CSN1, also known as GPS1) and ERGIC-53 (also known as LMAN1). A direct interaction between IFT20 and both IFT54 and GMAP-210 was confirmed in pulldown assays. Confocal imaging of antigen-specific conjugates using T cells depleted of these proteins by RNA interference showed that TCR accumulation and phosphotyrosine signalling at the IS were impaired in the absence of IFT54, ARPC3 or ERGIC-53. Similar to in IFT20-deficient T cells, this defect resulted from a reduced ability of endosomal TCRs to polarize to the IS despite a correct translocation of the centrosome towards the antigen-presenting cell contact. Our data underscore the traffic-related role of an IFT20 complex that includes components of the intracellular trafficking machinery in IS assembly.

Vesicular Trafficking to the Immune Synapse: How to Assemble Receptor-Tailored Pathways from a Basic Building Set

The signals that orchestrate T-cell activation are coordinated within a highly organized interface with the antigen-presenting cell (APC), known as the immune synapse (IS). IS assembly depends on T-cell antigen receptor engagement by a specific peptide antigen-major histocompatibility complex ligand. This primary event leads to polarized trafficking of receptors and signaling mediators associated with recycling endosomes to the cellular interface, which contributes to IS assembly as well as signal termination and favors information transfer from T cells to APCs. Here, we will review recent advances on the vesicular pathways implicated in IS assembly and maintenance, focusing on the spatiotemporal regulation of the traffic of specific receptors by Rab GTPases. Based on accumulating evidence that the IS is a functional homolog of the primary cilium, which coordinates several central signaling pathways in ciliated cells, we will also discuss the similarities in the mechanisms regulating vesicular trafficking to these specialized membrane domains.

Burkitt lymphoma beyond MYC translocation: N-MYC and DNA methyltransferases dysregulation

Background

The oncogenic transcription factor MYC is pathologically activated in many human malignancies. A paradigm for MYC dysregulation is offered by Burkitt lymphoma, where chromosomal translocations leading to Immunoglobulin gene-MYC fusion are the crucial initiating oncogenic events. However, Burkitt lymphoma cases with no detectable MYC rearrangement but maintaining MYC expression have been identified and alternative mechanisms can be involved in MYC dysregulation in these cases.

Methods

We studied the microRNA profile of MYC translocation-positive and MYC translocation-negative Burkitt lymphoma cases in order to uncover possible differences at the molecular level. Data was validated at the mRNA and protein level by quantitative Real-Time polymerase chain reaction and immunohistochemistry, respectively.

Results

We identified four microRNAs differentially expressed between the two groups. The impact of these microRNAs on the expression of selected genes was then investigated. Interestingly, in MYC translocation-negative cases we found over-expression of DNA-methyl transferase family members, consistent to hypo-expression of the hsa-miR-29 family. This finding suggests an alternative way for the activation of lymphomagenesis in these cases, based on global changes in methylation landscape, aberrant DNA hypermethylation, lack of epigenetic control on transcription of targeted genes, and increase of genomic instability. In addition, we observed an over-expression of another MYC family gene member, MYCN that may therefore represent a cooperating mechanism of MYC in driving the malignant transformation in those cases lacking an identifiable MYC translocation but expressing the gene at the mRNA and protein levels.

Conclusions

Collectively, our results showed that MYC translocation-positive and MYC translocation-negative Burkitt lymphoma cases are slightly different in terms of microRNA and gene expression. MYC translocation-negative Burkitt lymphoma, similarly to other aggressive B-cell non Hodgkin’s lymphomas, may represent a model to understand the intricate molecular pathway responsible for MYC dysregulation in cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1661-7) contains supplementary material, which is available to authorized users.

The small GTPase Rab29 is a common regulator of immune synapse assembly and ciliogenesis

Accumulating evidence underscores the T-cell immune synapse (IS) as a site of intense vesicular trafficking, on which productive signaling and cell activation crucially depend. Although the T-cell antigen receptor (TCR) is known to exploit recycling to accumulate to the IS, the specific pathway that controls this process remains to be elucidated. Here we demonstrate that the small GTPase Rab29 is centrally implicated in TCR trafficking and IS assembly. Rab29 colocalized and interacted with Rab8, Rab11 and IFT20, a component of the intraflagellar transport system that regulates ciliogenesis and participates in TCR recycling in the non-ciliated T cell, as assessed by co-immunoprecipitation and immunofluorescence analysis. Rab29 depletion resulted in the inability of TCRs to undergo recycling to the IS, thereby compromizing IS assembly. Under these conditions, recycling TCRs accumulated in Rab11(+) endosomes that failed to polarize to the IS due to defective Rab29-dependent recruitment of the dynein microtubule motor. Remarkably, Rab29 participates in a similar pathway in ciliated cells to promote primary cilium growth and ciliary localization of Smoothened. These results provide a function for Rab29 as a regulator of receptor recycling and identify this GTPase as a shared participant in IS and primary cilium assembly.

Regulation of vesicular traffic at the T cell immune synapse: lessons from the primary cilium

The signals that orchestrate the process of T cell activation are coordinated at the specialized interface that forms upon contact with an antigen presenting cell displaying a specific MHC-associated peptide ligand, known as the immune synapse. The central role of vesicular traffic in the assembly of the immune synapse has emerged only in recent years with the finding that sustained T-cell receptor (TCR) signaling involves delivery of TCR/CD3 complexes from an intracellular pool associated with recycling endosomes. A number of receptors as well as membrane-associated signaling mediators have since been demonstrated to exploit this process to localize to the immune synapse. Here, we will review our current understanding of the mechanisms responsible for TCR recycling, with a focus on the intraflagellar transport system, a multimolecular complex that is responsible for the assembly and function of the primary cilium which we have recently implicated in polarized endosome recycling to the immune synapse.

HIV-1 Tat induces DNMT over-expression through microRNA dysregulation in HIV-related non Hodgkin lymphomas

BACKGROUND

A close association between HIV infection and the development of cancer exists. Although the advent of highly active antiretroviral therapy has changed the epidemiology of AIDS-associated malignancies, a better understanding on how HIV can induce malignant transformation will help the development of novel therapeutic agents.

METHODS

HIV has been reported to induce the expression of DNMT1 in vitro, but still no information is available about the mechanisms regulating DNMT expression in HIV-related B-cell lymphomas. In this paper, we investigated the expression of DNMT family members (DNMT1, DNMT3a/b) in primary cases of aggressive B-cell lymphomas of HIV-positive subjects.

RESULTS

Our results confirmed the activation of DNMT1 by HIV in vivo, and reported for the first time a marked up-regulation of DNMT3a and DNMT3b in HIV-positive aggressive B-cell lymphomas. DNMT up-regulation in HIV-positive tumors correlated with down-regulation of specific microRNAs, as the miR29 family, the miR148-152 cluster, known to regulate their expression. Literature reports the activation of DNMTs by the human polyomavirus BKV large T-antigen and adenovirus E1a, through the pRb/E2F pathway. We have previously demonstrated that the HIV Tat protein is able to bind to the pocket proteins and to inactivate their oncosuppressive properties, resulting in uncontrolled cell proliferation. Therefore, we focused on the role of Tat, due to its capability to be released from infected cells and to dysregulate uninfected ones, using an in vitro model in which Tat was ectopically expressed in B-cells.

CONCLUSIONS

Our findings demonstrated that the ectopic expression of Tat was per se sufficient to determine DNMT up-regulation, based on microRNA down-regulation, and that this results in aberrant hypermethylation of target genes and microRNAs. These results point at a direct role for Tat in participating in uninfected B-cell lymphomagenesis, through dysregulation of the epigenetical control of gene expression.

The effects of HIV-1 Tat protein on cell cycle during cervical carcinogenesis

The role of HPV in the carcinogenesis of intraepithelial and invasive anogenital lesions is currently well established. E6 and E7 oncoproteins of high-risk HPV genotypes are known to inactivate p53 and pRb pathways. Several studies have described an increased prevalence and recurrence of both cervical HPV infection and invasive cervical cancer among HIV-1 positive women compared to HIV-1 negative cases. For these reasons, cervical cancer is considered an AIDS-defining neoplasm. Unlike other AIDS-associated neoplasms, the occurrence of cervical cancer is independent of immune suppression. HIV-1 infection in patients with high grade precancerous lesions and invasive cervical cancers results in a therapy refractory and more aggressive disease phenotype, which is not yet well understood at the molecular level. An upregulation of HPV E6 and E7 gene expressions by HIV-1 proteins such as Tat has been documented by some authors. However, the role of HIV-1 in cervical carcinomas is still unclear. It is already known that HIV-1 Tat protein is able to influence cell cycle progression. Altogether, these facts led us to investigate the effects of Tat on the expression of cell cycle regulator genes. After transfection of HeLa cells with Tat, we analyzed the expression of cell cycle regulators from these cells by IHC and Real-time PCR. A significant reduction in the expression of cell cycle inhibitors of transcription and an increase in the levels of proliferation markers were observed. These results suggest that HIV-1 may enhance cervical carcinogenesis by promoting cell cycle progression. We also found that this HIV-1 Tat-induced cell proliferation was not dependent on the E2F family of transcription factors, and therefore postulate that Sp factors may be involved.

The Epstein Barr-encoded BART-6-3p microRNA affects regulation of cell growth and immuno response in Burkitt lymphoma

Background

Burkitt lymphoma is an aggressive B-cell lymphoma presenting in three clinical forms: endemic, sporadic and immunodeficiency-associated. More than 90% of endemic Burkitt lymphoma carry latent Epstein-Barr virus, whereas only 20% of sporadic Burkitt lymphoma are associated with Epstein-Barr infection. Although the Epstein-Barr virus is highly related with the endemic form, how and whether the virus participates in its pathogenesis remains to be fully elucidated. In particular, the virus may impair cellular gene expression by its own encoded microRNAs.

Methods

Using microRNA profiling we compared Epstein-Barr-positive and Epstein-Barr-negative Burkitt lymphoma cases for both cellular and viral microRNAs. The array results were validated by qRT-PCR, and potential targets of viral microRNAs were then searched by bioinformatic predictions, and classified in functional categories, according to the Gene Ontology. Our findings were validated by in vitro functional studies and by immunohistochemistry on a larger series of cases.

Results

We showed that a few cellular microRNAs are differentially expressed between Epstein-Barr-positive and Epstein-Barr-negative Burkitt lymphoma cases, and identified a subset of viral microRNAs expressed in Epstein-Barr-positive Burkitt lymphomas. Of these, we characterized the effects of viral BART6-3p on regulation of cellular genes. In particular, we analyzed the IL-6 receptor genes (IL-6Rα and IL-6ST), PTEN and WT1 expression for their possible relevance to Burkitt lymphoma. By means of immunohistochemistry, we observed a down-regulation of the IL-6 receptor and PTEN specifically in Epstein-Barr-positive Burkitt lymphoma cases, which may result in the impairment of key cellular pathways and may contribute to malignant transformation. On the contrary, no differences were observed between Epstein-Barr-positive and Epstein-Barr-negative Burkitt lymphoma cases for WT1 expression.

Conclusions

Our preliminary results point at an active role for the Epstein-Barr virus in Burkitt lymphomagenesis and suggest new possible mechanisms used by the virus in determining dysregulation of the host cell physiology.

Specific recycling receptors are targeted to the immune synapse by the intraflagellar transport system

T cell activation requires sustained signaling at the immune synapse, a specialized interface with the antigen-presenting cell (APC) that assembles following T cell antigen receptor (TCR) engagement by major histocompatibility complex (MHC)-bound peptide. Central to sustained signaling is the continuous recruitment of TCRs to the immune synapse. These TCRs are partly mobilized from an endosomal pool by polarized recycling. We have identified IFT20, a component of the intraflagellar transport (IFT) system that controls ciliogenesis, as a central regulator of TCR recycling to the immune synapse. Here, we have investigated the interplay of IFT20 with the Rab GTPase network that controls recycling. We found that IFT20 forms a complex with Rab5 and the TCR on early endosomes. IFT20 knockdown (IFT20KD) resulted in a block in the recycling pathway, leading to a build-up of recycling TCRs in Rab5(+) endosomes. Recycling of the transferrin receptor (TfR), but not of CXCR4, was disrupted by IFT20 deficiency. The IFT components IFT52 and IFT57 were found to act together with IFT20 to regulate TCR and TfR recycling. The results provide novel insights into the mechanisms that control TCR recycling and immune synapse assembly, and underscore the trafficking-related function of the IFT system beyond ciliogenesis.

Epstein-Barr nuclear antigen 1 induces expression of the cellular microRNA hsa-miR-127 and impairing B-cell differentiation in EBV-infected memory B cells. New insights into the pathogenesis of Burkitt lymphoma

Epstein-Barr Virus (EBV) is a γ-herpesvirus that infects >90% of the human population. Although EBV persists in its latent form in healthy carriers, the virus is also associated with several human cancers. EBV is strongly associated with Burkitt lymphoma (BL), even though there is still no satisfactory explanation of how EBV participates in BL pathogenesis. However, new insights into the interplay between viruses and microRNAs (miRNAs) have recently been proposed. In particular, it has been shown that B-cell differentiation in EBV-positive BL is impaired at the post-transcriptional level by altered expression of hsa-miR-127. Here, we show that the overexpression of hsa-miR-127 is due to the presence of the EBV-encoded nuclear antigen 1 (EBNA1) and give evidence of a novel mechanism of direct regulation of the human miRNA by this viral product. Finally, we show that the combinatorial expression of EBNA1 and hsa-miR-127 affects the expression of master B-cell regulators in human memory B cells, confirming the scenario previously observed in EBV-positive BL primary tumors and cell lines. A good understanding of these mechanisms will help to clarify the complex regulatory networks between host and pathogen, and favor the design of more specific treatments for EBV-associated malignancies.

Alteration of microRNAs regulated by c-Myc in Burkitt lymphoma

Background

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma, with a characteristic clinical presentation, morphology and immunophenotype. Over the past years, the typical translocation t(8;14) and its variants have been considered the molecular hallmark of this tumor. However, BL cases with no detectable MYC rearrangement have been identified. Intriguingly, these cases express MYC at levels comparable with cases carrying the translocation. In normal cells c-Myc expression is tightly regulated through a complex feedback loop mechanism. In cancer, MYC is often dysregulated, commonly due to genomic abnormalities. It has recently emerged that this phenomenon may rely on an alteration of post-transcriptional regulation mediated by microRNAs (miRNAs), whose functional alterations are associated with neoplastic transformation. It is also emerging that c-Myc modulates miRNA expression, revealing an intriguing crosstalk between c-Myc and miRNAs.

Principal Findings

Here, we investigated the expression of miRNAs possibly regulated by c-Myc in BL cases positive or negative for the translocation. A common trend of miRNA expression, with the exception of hsa-miR-9*, was observed in all of the cases. Intriguingly, down-regulation of this miRNA seems to specifically identify a particular subset of BL cases, lacking MYC translocation. Here, we provided evidence that hsa-miR-9-1 gene is heavily methylated in those cases. Finally, we showed that hsa-miR-9* is able to modulate E2F1 and c-Myc expression.

Conclusions

Particularly, this study identifies hsa-miR-9* as potentially relevant for malignant transformation in BL cases with no detectable MYC translocation. Deregulation of hsa-miR-9* may therefore be useful as a diagnostic tool, suggesting it as a promising novel candidate for tumor cell marker.

Geographic variation and environmental conditions as cofactors in Chlamydia psittaci association with ocular adnexal lymphomas: a comparison between Italian and African samples

A particular extra-nodal lymphoma type arises from B cells of the marginal zone (MZ) of mucosa-associated lymphoid tissue (MALT). The aetiology of MZ lymphomas suggests that they are associated with chronic antigenic stimulation by microbial pathogens, among which Helicobacter pylori-associated gastric MALT lymphoma is the best studied. Recently, MALT lymphomas have been described in the context of chronic conjunctivitis, which can be associated with Chlamydia spp. infection. Studies from Italy showed the presence of Chlamydia psittaci in 87% of ocular adnexal lymphomas (OAL), and C. psittaci has been described in a large part of samples from Austria and Korea as well. However, this finding was not always confirmed by other studies, suggesting that the association with C. psittaci may depend on geographic heterogeneity. Interestingly, none of the studies up to now has been carried out in the African population, where a strong association between infectious agents and the occurrence of human neoplasms has been reported. This study was designed to investigate the possible association of Chlamydia psittaci in cases retrieved from Kenya, compared to cases from Italy. Our results showed that there was a marked variation between the two geographical areas in terms of association with C. psittaci, as 17% (5/30) of the samples from Italy were positive for C. psittaci, whereas no association with this pathogen was observed in any of the African samples (0/9), suggesting that other cofactors may determine the OAL occurrence in those areas. OAL cases are often characterized by down-regulation of p16/INK4a expression and promoter hypermethylation of the p16/INK4a gene. Our results showed a partial methylation of p16/INK4a promoter in C. psittaci-negative cases, whereas no hypermethylation of this gene was found in C. psittaci-positive cases, suggesting that mechanisms other than promoter hypermethylation lead to p16/INK4a silencing in C. psittaci-positive cases. We may conclude that the role of epidemiologic, environmental and genetic factors, must be considered in the aetiology of this disease.

Downregulation and aberrant promoter methylation of p16INK4A: a possible novel heritable susceptibility marker to retinoblastoma

RB loss has long been recognized as the causative genetic alteration underlying retinoblastoma but it is increasingly evident that other alterations are required for the tumor to develop. Therefore, we set out to identify additional inheritable susceptibility markers and new potential preventive and therapeutic targets for retinoblastoma. We focused on the p16INK4A tumor suppressor gene because of its possible role in retinoblastoma pathogenesis and its involvement in predisposition to familial cancer. p16INK4A expression was analyzed in tumor samples from retinoblastoma patients by immunohistochemistry and in peripheral blood cells from both patients and their parents by real-time quantitative reverse transcription-PCR (qRT-PCR). Since promoter methylation is a common mechanism regulating p16INK4A expression, the methylation status of its promoter was also analyzed in blood samples from patients and their parents by methylation-specific PCR. A downregulation of p16INK4A was observed in 55% of retinoblastoma patients. Interestingly, in 56% of the cases showing p16INK4A downregulation at least one of the patients' parents bore the same alteration in blood cells. Analysis of p16INK4A promoter methylation showed hypermethylation in most patients with p16INK4A downregulation and in the parents with the same alteration in p16INK4A expression. The finding that p16INK4A was downregulated both in patients and their parents suggests that this alteration could be a novel inheritable susceptibility marker to retinoblastoma. The observation that p16INK4A downregulation seems to be due to its promoter hypermethylation opens the way for the development of new preventive and therapeutic strategies using demethylating agents.

B-cell differentiation in EBV-positive Burkitt lymphoma is impaired at posttranscriptional level by miRNA-altered expression

Endemic, sporadic and HIV-associated Burkitt lymphoma (BL) all have a B-cell phenotype and a MYC translocation, but a variable association with the Epstein-Barr virus (EBV). However, there is still no satisfactory explanation of how EBV participates in the pathogenesis of BL. A recent investigation suggested that EBV-positive and EBV-negative BL have different cells of origin. In particular, according to immunoglobulin gene mutation analysis, EBV-negative BLs may originate from early centroblasts, whereas EBV-positive BLs seem to arise from postgerminal center B cells or memory B cells. The appearance of a germinal center phenotype in EBV-positive cells might thus derive from a block in B-cell differentiation. The exit from the germinal center involves a complex series of events, which require the activation of BLIMP-1, and the consequent downregulation of several target genes. Here, we investigated the expression of specific miRNAs predicted to be involved in B-cell differentiation and found that hsa-miR-127 is differentially expressed between EBV-positive and EBV-negative BLs. In particular, it was strongly upregulated only in EBV-positive BL samples, whereas EBV-negative cases showed levels of expression similar to normal controls, including microdissected germinal centers (GC) cells. In addition, we found evidence that hsa-miR-127 is involved in B-cell differentiation process through posttranscriptional regulation of BLIMP1 and XBP1. The overexpression of this miRNA may thus represent a key event in the lymphomagenesis of EBV positive BL, by blocking the B-cell differentiation process.

Rare lymphoid neoplasms coexpressing B- and T-cell antigens. The role of PAX-5 gene methylation in their pathogenesis

We report 3 cases of lymphoid neoplasms with mixed lineage features of T-, NK-, or B-cell marker expression and clonal gene rearrangement for both T-cell receptor and immunoglobulin light chain IgK. A characteristic of our cases was the lack of expression of the specific B-cell transcription factor, Pax5, which is essential for maintaining the identity and function of mature B cells during late B lymphopoiesis. In the absence of Pax5, B cells in vitro can differentiate into macrophages, dendritic cells, granulocytes, and T/NK cells. Methylation analysis of the Pax5 gene in our cases suggests that its inactivation by this epigenetic event in a committed or mature B cell, before plasma cell differentiation, may well be a common pathogenetic mechanism in mature lymphoid neoplasms with expression of multilineage antigens. In particular, case 1 may represent a mixed NK- and B-cell lineage; and cases 2 and 3 may represent mixed T and B-cell lineage, respectively. Aberrations in the DNA methylation patterns are currently recognized as a hallmark of human cancer. Cases with aberrant phenotypes require molecular analysis for lineage assignment. Studies of such cases may be helpful to better elucidate whether they represent a distinct entity with clinical, immunophenotypic, and molecular characteristics or an incidental phenomenon during malignant transformation. Interestingly, these cases were all characterized by poor clinical outcome.

MYC translocation-negative classical Burkitt lymphoma cases: an alternative pathogenetic mechanism involving miRNA deregulation

The molecular feature of Burkitt lymphoma (BL) is the translocation that places c-Myc under the control of immunoglobulin gene regulatory elements. However, there is accumulating evidence that some cases may lack an identifiable MYC translocation. In addition, during the EUROFISH project, aiming at the standardization of FISH procedures in lymphoma diagnosis, we found that five cases out of 35 classic endemic BLs were negative for MYC translocations by using a split-signal as well as a dual-fusion probe. Here we investigated the expression pattern of miRNAs predicted to target c-Myc, in BL cases, to clarify whether alternative pathogenetic mechanisms may be responsible for lymphomagenesis in cases lacking the MYC translocation. miRNAs are a class of small RNAs that are able to regulate gene expression at the post-transcriptional level. Several studies have reported their involvement in cancer and their association with fragile sites in the genome. They have also been shown to control cell growth, differentiation, and apoptosis, suggesting that these molecules could act as tumour suppressors or oncogenes. Our results demonstrated a modulation of specific miRNAs. In particular, down-regulation of hsa-let-7c was observed in BL cases, compared to normal controls. More interestingly, hsa-mir-34b was found to be down-regulated only in BL cases that were negative for MYC translocation, suggesting that this event might be responsible for c-Myc deregulation in such cases. This hypothesis was further confirmed by our in vitro experiments, which demonstrated that increasing doses of synthetic hsa-mir-34b were able to modulate c-Myc expression. These results indicate for the first time that hsa-mir-34b may influence c-Myc expression in Burkitt lymphoma as the more common aberrant control exercised by the immunoglobulin enhancer locus.

The role of the Cdk9/Cyclin T1 complex in T cell differentiation

The Cdk9/Cyclin T1 complex is very important in controlling specific differentiative pathways of several cell types, including muscle cells and neurons. We recently demonstrated the involvement of this complex in B cell activation/differentiation. To check whether the Cdk9/Cyclin T1 complex is also involved in the T cell activation/differentiation process, we isolated different T cell populations by magnetic separation, based on their surface antigens. We observed that the expression level of Cdk9/Cyclin T1 increases in effector T cells (CD27(+)), as well as in activated T cells (CD25(+)) and memory T cells (CD45RA(-)), thus suggesting a specific upregulation of the Cdk9/Cyclin T1 complex following antigen encounter. We have previously demonstrated that in B cells, Cdk9 interacts in vivo with the E2A gene products E12/E47 (members of the basic helix-loop-helix family) which are involved in differentiation. In this article, we show that this interaction also occurs in T cells. This suggests an active role for the Cdk9/Cyclin T1 complex during lymphoid differentiation, through physical binding with E12 and E47. These preliminary results suggest that the Cdk9/Cyclin T1 complex may be important in the activation and differentiation program of lymphoid cells and that its upregulation, which is due to still unknown mechanisms, may contribute to malignant transformation.

Gene-expression analysis identifies novel RBL2/p130 target genes in endemic Burkitt lymphoma cell lines and primary tumors

Burkitt lymphoma (BL) is a B-cell tumor whose characteristic gene aberration is the translocation t(8;14), which determines c-myc overexpression. Several genetic and epigenetic alterations other than c-myc overexpression have also been described in BL. It has been demonstrated that the RBL2/p130 gene, a member of the retinoblastoma family (pRbs), is mutated in BL cell lines and primary tumors. The aim of this study was to investigate the biologic effect of RBL2/p130 in BL cells and its possible role in lymphomagenesis. Therefore, we reintroduced a functional RBL2/p130 in BL cell lines where this gene was mutated. Our results demonstrated that RBL2/p130-transfected cells regain growth control. This suggests that RBL2/p130 may control the expression of several genes, which may be important for cell growth and viability. Gene-expression analysis revealed a modulation of several genes, including CGRRF1, RGS1, BTG1, TIA1, and PCDHA2, upon RBL2/p130 reintroduction. We then monitored their expression in primary tumors of endemic BL as well, demonstrating that their expression resembled those of the BL cell lines. In conclusion, these data suggest that, as RBL2/p130 modulates the expression of target genes, which are important for cell growth and viability, its inactivation may be relevant for the occurrence of BL.

[On the job training at construction sites of the hospital corporation of Careggi (Florence)]

The "Careggi Safety" project has like objective to guarantee the safety execution of Careggi Hospital (Florence) restoration and development works, thanks to an in itinere training program into building sites and through tutor figure using. The project aim is to overcomes traditional indoor training limits, not effective in complex and dynamics reality like as building sites, constrained by contracts deadline and high labour turnover (subcontracts) inside carry out process. Solutions chose are: (a) a training projected in itinere, following site works evolution and safety and coordination plan, and through a constant agreement between customer and operative enterprises; (b) a building site's tutor, standing beside workers during realization phases, contributing to form on respective safety carry out job. In to "Careggi Safety" project training has been chose as preliminary and obligatory condition for labours admission and control into the building site.

Titration biosensors for the estimation of the biochemical nitrate demand of municipal and industrial wastes

An anoxic titrimetric test was investigated for measuring denitrification potential of different wastewaters, both municipal and industrial, and to quantify the denitrifying activity in an activated sludge system. The method measures the amount of acid that is required to maintain the pH set-point value in a batch denitrification experiment, and it was performed using a DENICON (denitrification controller) biosensor. The amount of acid is proportional to the nitrate used to oxidise the biodegradable chemical oxygen demand present in the wastewater, while the acid consumption rate is used to derive the denitrifying activity. The wastewaters tested were a municipal wastewater (MW), an industrial-municipal wastewater (MIW; 70% and 30%, respectively), and four industrial wastewaters drawn from an ice-cream factory (IW1), a beet-sugar factory (IW2), a brewery (IW3), and a tuna cannery industry (IW4). Good correlation between titration data and analyses was found.

Use of industrial wastewaters for the optimization and control of nitrogen removal processes

In this experimental study the characterization of 2 industrial wastewaters, coming from an ice cream production industry (IW1) and a beet-sugar factory (IW2), with respect to their readily biodegradable fraction and denitrification potential, has been performed. To this end physical-chemical and biological characterization methods, both anoxic and aerobic, were used. Moreover a pilot scale SBR fed with municipal wastewater was started to verify the effect of the gradual addition of the concentrated organic wastewaters during the anoxic phase. The SBR was initially fed only with a primary municipal wastewater, then the organic load was increased by adding to the feed, during the anoxic phase, a small amount of the IW1 (second period). Once the initial conditions were restored the load was again raised using the second industrial wastewater (IW2) (third period). With those additions the nitrogen removal efficiency increased from 26% to 50%, in the case of the IW1 and from 23% to 53% in the case of the wastewater IW2, without any negative effect on the global performance of the system. In addition, periodical kinetic studies of denitrification and nitrification in the SBR, were performed.

Hormonal replacement therapy and gynecological cancer

The problem of quality of life and lifestyle in elderly women is today a very important social problem all over the world but particularly in rich western countries. Life expectancy of the population will be longer and longer in the future and for both females and males the biological involution correlated with the aging process must be delayed. The gonadal hormones stimulate the healthy state of the entire body (heart, skin, brain, bones, urogenital apparatus and so on) and consequently hormonal replacement therapy (HRT) is mandatory. In women the biological clock of menopause allows us to intervene at the right time, with personalized estrogenic, estroprogestinic or estroandrogenic treatments. Health benefits and groundless risks allow today a careful hormonal management even in women treated for gynaecological cancers (breast and endometrium as well).

Mortality of Italian lead smelter workers

OBJECTIVES

The purpose of this study was to evaluate the health consequences of employment in the lead-smelting industry.

METHODS

A mortality study of 1388 workers and laborers in production and maintenance departments was conducted in an Italian lead-smelting plant. The vital status of cohort members was determined from 1950 to 1992. Standardized mortality ratios were calculated for specific causes of death on the basis of national and regional reference rates. The relative risk for selected causes of death was also modeled as a function of age, calendar period, latency, and duration of employment with Poisson regression analysis.

RESULTS

A significant 4.5-fold excess mortality from pneumoconiosis and other diseases of the respiratory system was observed, but the risk of pneumoconiosis did not show a significant trend by duration of employment. Mortality from all cancers, stomach cancer, and lung cancer was lower than expected. The standardized mortality ratios for genitourinary diseases and kidney cancer were not significantly elevated, but the Poisson regression analysis showed that both risks increased significantly by duration of employment.

CONCLUSIONS

These findings provide limited evidence that long-term employment in lead-smelting plants increases the risk of genitourinary diseases and kidney cancer. The observed increase in mortality from pneumoconiosis and other diseases of the respiratory system was more likely related to silica exposure in other workplaces.