Kamel Khalili

Publications of Kamel Khalili

• Integrating role of T-antigen, Rb2/p130, CTCF and BORIS in mediating non-canonical endoplasmic reticulum-dependent death pathways triggered by ER-chronic stress in mouse medulloblastoma.

  Authors: Marcella Macaluso, Valentina Caracciolo, Valeria Rizzo, Ang Sun, Micaela Montanari, Giuseppe Russo, Gianfranco Bellipanni, Kamel Khalili, Antonio Giordano

  Cell cycle (Georgetown, Tex.). 05/2012; 11(9).

  Distinct molecular pathways could be constitutively active in mouse T-Antigen positive and T-Antigen negative medulloblastoma cell lines, contributing to their phenotypic differences as well as toDistinct molecular pathways could be constitutively active in mouse T-Antigen positive and T-Antigen negative medulloblastoma cell lines, contributing to their phenotypic differences as well as to cellular responses, cell cycle progression, cell death and survival. The diversity of these responses may be due, at least in part, to distinct activities of Rb2/p130, CTCF and BORIS proteins in response to an altered network of signaling evoked by the T-Ag presence. Here, we provided evidence supporting a role for the T-Antigen in causing chronic endoplasmic reticulum (ER) stress and aberrant Caspase-12 expression and activation, subsequently driving to both massive cell death, and perhaps selection of cells with a higher malignant phenotype. Furthermore, we observed that the endoplasmic stress, either chronically caused by T-Ag or transiently induced by glucose deprivation, is accompanied by the formation of complexes between the retinoblastoma related protein Rb2/p130 and the chromatin insulator CCCTC-binding factor CTCF, or the CTCF-paralogue BORIS. Our study represents the first evidence supporting a role of the T-Antigen in inducing/maintaining chronic ER-stress, as well as, indicating a role of Rb2/p130, CTCF and BORIS as potential mediators of non-canonical ER-dependent death pathway in mouse medulloblastoma.

• MEKK1-MKK4-JNK-AP1 Pathway Negatively Regulates Rgs4 Expression in Colonic Smooth Muscle Cells.

  Authors: Yonggang Zhang, Fang Li, Shu Liu, Hong Wang, Sunila Mahavadi, Karnam S Murthy, Kamel Khalili, Wenhui Hu

  PloS one. 01/2012; 7(4):e35646.

  BACKGROUND: Regulator of G-protein Signaling 4 (RGS4) plays an important role in regulating smooth muscle contraction, cardiac development, neural plasticity and psychiatric disorder. However, theBACKGROUND: Regulator of G-protein Signaling 4 (RGS4) plays an important role in regulating smooth muscle contraction, cardiac development, neural plasticity and psychiatric disorder. However, the underlying regulatory mechanisms remain elusive. Our recent studies have shown that upregulation of Rgs4 by interleukin (IL)-1β is mediated by the activation of NFκB signaling and modulated by extracellular signal-regulated kinases, p38 mitogen-activated protein kinase, and phosphoinositide-3 kinase. Here we investigate the effect of the c-Jun N-terminal kinase (JNK) pathway on Rgs4 expression in rabbit colonic smooth muscle cells. METHODOLOGY/PRINCIPAL FINDINGS: Cultured cells at first passage were treated with or without IL-1β (10 ng/ml) in the presence or absence of the selective JNK inhibitor (SP600125) or JNK small hairpin RNA (shRNA). The expression levels of Rgs4 mRNA and protein were determined by real-time RT-PCR and Western blot respectively. SP600125 or JNK shRNA increased Rgs4 expression in the absence or presence of IL-1β stimulation. Overexpression of MEKK1, the key upstream kinase of JNK, inhibited Rgs4 expression, which was reversed by co-expression of JNK shRNA or dominant-negative mutants for MKK4 or JNK. Both constitutive and inducible upregulation of Rgs4 expression by SP600125 was significantly inhibited by pretreatment with the transcription inhibitor, actinomycin D. Dual reporter assay showed that pretreatment with SP600125 sensitized the promoter activity of Rgs4 in response to IL-1β. Mutation of the AP1-binding site within Rgs4 promoter increased the promoter activity. Western blot analysis confirmed that IL-1β treatment increased the phosphorylation of JNK, ATF-2 and c-Jun. Gel shift and chromatin immunoprecipitation assays validated that IL-1β increased the in vitro and ex vivo binding activities of AP1 within rabbit Rgs4 promoter. CONCLUSION/SIGNIFICANCE: Activation of MEKK1-MKK4-JNK-AP1 signal pathway plays a tonic inhibitory role in regulating Rgs4 transcription in rabbit colonic smooth muscle cells. This negative regulation may aid in maintaining the transient level of RGS4 expression.

• Oncogenic viruses and tumor glucose metabolism: like kids in a candy store.

  Authors: Evan Noch, Kamel Khalili

  Molecular cancer therapeutics. 01/2012; 11(1):14-23.

  Oncogenic viruses represent a significant public health burden in light of the multitude of malignancies that result from chronic or spontaneous viral infection and transformation. Although many ofOncogenic viruses represent a significant public health burden in light of the multitude of malignancies that result from chronic or spontaneous viral infection and transformation. Although many of the molecular signaling pathways that underlie virus-mediated cellular transformation are known, the impact of these viruses on metabolic signaling and phenotype within proliferating tumor cells is less well understood. Whether the interaction of oncogenic viruses with metabolic signaling pathways involves enhanced glucose uptake and glycolysis (both hallmark features of transformed cells) or dysregulation of molecular pathways that regulate oxidative stress, viruses are adept at facilitating tumor expansion. Through their effects on cell proliferation pathways, such as the PI3K and MAPK pathways, the cell cycle regulatory proteins p53 and ATM, and the cell stress response proteins HIF-1α and AMPK, viruses exert control over critical metabolic signaling cascades. Additionally, oncogenic viruses modulate the tumor metabolomic profile through direct and indirect interactions with glucose transporters, such as GLUT1, and specific glycolytic enzymes, including pyruvate kinase, glucose 6-phosphate dehydrogenase, and hexokinase. Through these pathways, oncogenic viruses alter the phenotypic characteristics and energy-use methods of transformed cells; therefore, it may be possible to develop novel antiglycolytic therapies to target these dysregulated pathways in virus-derived malignancies.

• JC Virus T-Antigen Regulates Glucose Metabolic Pathways in Brain Tumor Cells.

  Authors: Evan Noch, Ilker Kudret Sariyer, Jennifer Gordon, Kamel Khalili

  PloS one. 01/2012; 7(4):e35054.

  Recent studies have reported the detection of the human neurotropic virus, JCV, in a significant population of brain tumors, including medulloblastomas. Accordingly, expression of the JCV earlyRecent studies have reported the detection of the human neurotropic virus, JCV, in a significant population of brain tumors, including medulloblastomas. Accordingly, expression of the JCV early protein, T-antigen, which has transforming activity in cell culture and in transgenic mice, results in the development of a broad range of tumors of neural crest and glial origin. Evidently, the association of T-antigen with a range of tumor-suppressor proteins, including p53 and pRb, and signaling molecules, such as β-catenin and IRS-1, plays a role in the oncogenic function of JCV T-antigen. We demonstrate that T-antigen expression is suppressed by glucose deprivation in medulloblastoma cells and in glioblastoma xenografts that both endogenously express T-antigen. Mechanistic studies indicate that glucose deprivation-mediated suppression of T-antigen is partly influenced by 5'-activated AMP kinase (AMPK), an important sensor of the AMP/ATP ratio in cells. In addition, glucose deprivation-induced cell cycle arrest in the G1 phase is blocked with AMPK inhibition, which also prevents T-antigen downregulation. Furthermore, T-antigen prevents G1 arrest and sustains cells in the G2 phase during glucose deprivation. On a functional level, T-antigen downregulation is partially dependent on reactive oxygen species (ROS) production during glucose deprivation, and T-antigen prevents ROS induction, loss of ATP production, and cytotoxicity induced by glucose deprivation. Additionally, we have found that T-antigen is downregulated by the glycolytic inhibitor, 2-deoxy-D-glucose (2-DG), and the pentose phosphate inhibitors, 6-aminonicotinamide and oxythiamine, and that T-antigen modulates expression of the glycolytic enzyme, hexokinase 2 (HK2), and the pentose phosphate enzyme, transaldolase-1 (TALDO1), indicating a potential link between T-antigen and metabolic regulation. These studies point to the possible involvement of JCV T-antigen in medulloblastoma proliferation and the metabolic phenotype and may enhance our understanding of the role of viral proteins in glycolytic tumor metabolism, thus providing useful targets for the treatment of virus-induced tumors.

• Nuclear factor kappa B signaling initiates early differentiation of neural stem cells.

  Authors: Yonggang Zhang, Jianjun Liu, Shaohua Yao, Fang Li, Lin Xin, Mowen Lai, Valerie Bracchi-Ricard, Hong Xu, William Yen, Wentong Meng [......] Leiting Yang, Shaffiat Karmally, Jin Liu, Hongyan Zhu, Jennifer Gordon, Kamel Khalili, Shanthi Srinivasan, John R Bethea, Xianming Mo, Wenhui Hu

  Stem cells (Dayton, Ohio). 12/2011; 30(3):510-24.

  Inflammatory mediators, many of which activate the signaling of nuclear factor kappa B (NFκB), have received increasing attention in the field of neurogenesis. NFκB signaling regulates neuriteInflammatory mediators, many of which activate the signaling of nuclear factor kappa B (NFκB), have received increasing attention in the field of neurogenesis. NFκB signaling regulates neurite outgrowth and neural plasticity as well as the proliferation/apoptosis and terminal differentiation of neural stem cells (NSCs). Early neurogenesis from NSCs produces identical progeny through symmetric division and committed daughter cells through asymmetric division. Here, we show that NFκB signaling is required for NSC initial differentiation. The canonical IKKβ/IκBα/p65 pathway is activated during the initial stages of neural differentiation induced by treatment with TNFα or withdrawal of epidermal growth factor/basic fibroblast growth factor. NSC-specific inhibition of NFκB in transgenic mice causes an accumulation of Nestin(+) /Sox2(+) /glial fibrillary acidic protein(+) NSCs. Inhibition of NFκB signaling in vitro blocks differentiation and asymmetric division and maintains NSCs in an undifferentiated state. The induction of initial differentiation and asymmetry by NFκB signaling occurs through the inhibition of C/EBPβ expression. Our data reveal a novel function of NFκB signaling in early neurogenesis and provide insight into the molecular mechanisms underlying neurodevelopmental disorders and neurodegenerative diseases. STEM CELLS 2012;30:510-524.

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• Growth inhibition of malignant glioblastoma by DING protein.

  Authors: Markus J Bookland, Nune Darbinian, Michael Weaver, Shohreh Amini, Kamel Khalili

  Journal of neuro-oncology. 11/2011; 107(2):247-56.

  Malignant gliomas are a highly aggressive type of brain tumor with extremely poor prognosis. These tumors are highly invasive and are often surgically incurable and resistant to chemotherapeutics andMalignant gliomas are a highly aggressive type of brain tumor with extremely poor prognosis. These tumors are highly invasive and are often surgically incurable and resistant to chemotherapeutics and radiotherapy. Thus, novel therapies that target pathways involved in growth and survival of the tumor cells are required for the treatment of this class of brain tumors. Previous studies revealed that epidermal growth factor receptor and extracellular-signal-regulated kinases (ERKs), which are involved in the induction of cell proliferation, are activated in the most aggressive type of glioma, i.e. glioblastoma multiforme (GBM). In fact, GBMs with increased levels of ERK activity exhibit a more aggressive phenotype than the others with moderate ERK activity, pointing to the importance of ERK and its kinase activity in the development and progression of these tumors. In this study, we have evaluated the effect of p38SJ, a novel member of the DING family of proteins, derived from Hypericum perforatum calluses, on the growth of malignant glioma cell lines, T98G and U-87MG by focusing on cell cycle and signaling pathways controlled by phosphorylation of various regulatory proteins including ERK. p38SJ, which exhibits profound phosphatase activity, shows the capacity to affect the phosphorylation status of several important kinases modulating signaling pathways, and cell growth and proliferation. Our results demonstrate that p38SJ reduces glioma cell viability and arrests cell cycle progression at G0/G1. The observed growth inhibitory effect of p38SJ is likely mediated by the downregulation of several cell cycle gatekeeper proteins, including cyclin E, Cdc2, and E2F-1. These results suggest that p38SJ may serve as a potential candidate for development of a therapeutic agent for the direct treatment of malignant gliomas and/or as a potential radiosensitizer.

• JCV agnoprotein-induced reduction in CXCL5/LIX secretion by oligodendrocytes is associated with activation of apoptotic signaling in neurons.

  Authors: Nana Merabova, Rafal Kaminski, Barbara Krynska, Shohreh Amini, Kamel Khalili, Armine Darbinyan

  Journal of cellular physiology. 10/2011;

  An indispensable role for oligodendrocytes in the protection of axon function and promotion of neuronal survival is strongly supported by the finding of progressive neuron/axon degeneration in humanAn indispensable role for oligodendrocytes in the protection of axon function and promotion of neuronal survival is strongly supported by the finding of progressive neuron/axon degeneration in human neurological diseases that affect oligodendrocytes. Imaging and pathological studies of the CNS have shown the presence of neuroaxonal injury in progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the CNS, resulting from destruction of oligodendrocytes upon productive replication of the pathogenic neurotropic polyomavirus JC. Here, we examined the extracellular factors involved in communication between oligodendrocytes and neurons. Culturing cortical neurons with conditioned medium (CM) from rat CG4 oligodendrocytic cells that express the JCV agnoprotein showed that CXCL5/LIX, which is a chemokine closely related to the human CXCL5/ENA78 and CXCL6/GCP-2 chemokines, is essential for neuronal cell survival. We found that in CM from agnoprotein-producing CG-4 cells level of CXC5/LIX is decreased compared to control cells. We also demonstrated that a reduced expression of CXCL5/LIX by CG4 GFP-Agno cells triggered a cascade of signaling events in cortical neurons. Analysis of mitogen-activated protein kinases (MAPK) and glycogen synthase kinase (GSK3) pathways showed that they are involved in mechanisms of neuronal apoptosis in response to the depletion of CXCL5/LIX signaling. These data suggest that agnoprotein-induced dysregulation of chemokine production by oligodendrocytes may contribute to neuronal/axonal injury in the pathogenesis of PML lesions. J. Cell. Physiol. © 2011 Wiley Periodicals, Inc.

• Epigenetics of µ-opioid receptors: Intersection with HIV-1 infection of the central nervous system.

  Authors: Patrick M Regan, Rajnish S Dave, Prasun K Datta, Kamel Khalili

  Journal of cellular physiology. 10/2011;

  The abuse of intravenous drugs, such as heroin, has become a major public health concern due to the increased risk of HIV-1 infection. Opioids such as heroin were originally identified andThe abuse of intravenous drugs, such as heroin, has become a major public health concern due to the increased risk of HIV-1 infection. Opioids such as heroin were originally identified and subsequently abused for their analgesic effects. However, many investigations have found additional effects of opioids, including regulation of the immune system. As such, chronic opioid abuse has been shown to promote HIV-1 pathogenesis and facilitate HIV-1-associated neurocognitive dysfunction. Clinical opioids, such as morphine and methadone, as well as illicit opioids, such as heroin, exert their effects primarily through interactions with the µ-opioid receptor (MOR). However, the mechanisms by which opioids enhance neurocognitive dysfunction through MOR-mediated signaling pathways are not completely understood. New findings in the regulation of MOR expression, particularly epigenetic and transcriptional regulation as well as alternative splicing, sheds new insights into possible mechanisms of HIV-1 and opiate synergy. In this review, we identify mechanisms regulating MOR expression and propose novel mechanisms by which opioids and HIV-1 may modulate this regulation. Additionally, we suggest that differential regulation of newly identified MOR isoforms by opioids and HIV-1 has functional consequence in enhancing HIV-1 neurocognitive dysfunction. J. Cell. Physiol. © 2011 Wiley Periodicals, Inc.

• Progressive multifocal leukoencephalopathy: clinical and molecular aspects.

  Authors: Eleonora Tavazzi, Martyn K White, Kamel Khalili

  Reviews in medical virology. 09/2011; 22(1):18-32.

  The fatal CNS demyelinating disease, progressive multifocal leukoencephalopathy (PML), is rare and appears to occur almost always as a consequence of immune dysfunction. Thus, it is associated withThe fatal CNS demyelinating disease, progressive multifocal leukoencephalopathy (PML), is rare and appears to occur almost always as a consequence of immune dysfunction. Thus, it is associated with HIV/AIDS and also as a side effect of certain immunomodulatory monoclonal antibody therapies. In contrast to the rarity of PML, the etiological agent of the disease, the polyomavirus JC (JCV), is widespread in populations worldwide. In the 40 years since JCV was first isolated, much has been learned about the virus and the disease from laboratory and clinical observations. However, there are many aspects of the viral life cycle and of the pathogenesis of the disease that remain unclear, and our understanding is constantly evolving. In this review, we will discuss our current understanding of the clinical features of PML and molecular characteristics of JCV and of how they relate to each other. Clinical observations can inform molecular studies of the virus, and likewise, molecular findings concerning the life cycle of the virus can guide the development of novel therapeutic strategies.

• BAG3 protein is overexpressed in human glioblastoma and is a potential target for therapy.

  Authors: Michelina Festa, Luis Del Valle, Kamel Khalili, Renato Franco, Giosuè Scognamiglio, Vincenzo Graziano, Vincenzo De Laurenzi, Maria Caterina Turco, Alessandra Rosati

  The American journal of pathology. 06/2011; 178(6):2504-12.

  Glioblastoma multiforme, which represents 80% of malignant gliomas, is characterized by aggressiveness and high recurrence rates. Despite therapeutic advances, patients with glioblastoma multiformeGlioblastoma multiforme, which represents 80% of malignant gliomas, is characterized by aggressiveness and high recurrence rates. Despite therapeutic advances, patients with glioblastoma multiforme show a poor survival, and identification of novel markers and molecular targets for therapy is needed. A role for BAG3, a member of the BAG family of HSC/HSP70 co-chaperones, in promoting tumor cell growth in vivo has recently been described. We analyzed BAG3 levels by IHC in specimens from patients affected by brain tumors and we found that BAG3, although negative in normal brain tissues, was highly expressed in astrocytic tumors and increasingly expressed in more aggressive types of cancer; it was particularly high in glioblastomas. Down-regulating BAG3 both in vitro and in vivo in a rat glioblastoma model resulted in increased sensitivity to apoptosis, suggesting that BAG3 is a potential target for novel therapies. Finally, we determined that the underlying molecular mechanism requires the formation of a complex of BAG3, HSP70, and BAX that prevents BAX translocation to mitochondria, thus protecting tumor cells from apoptosis. Our data identify BAG3 as a potential marker of glial brain tumor sensitivity to therapy and thus also an attractive candidate for new molecular therapies.

• Pathogenesis of progressive multifocal leukoencephalopathy--revisited.

  Authors: Martyn K White, Kamel Khalili

  The Journal of infectious diseases. 03/2011; 203(5):578-86.

  Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system that is rare even though the proven etiological agent of PML, the polyomavirus JC (JC virus),Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system that is rare even though the proven etiological agent of PML, the polyomavirus JC (JC virus), is ubiquitous within the human population. The common feature of PML cases appears to be underlying immunosuppression, and PML has gained clinical visibility because of its association with human immunodeficiency virus and AIDS and its occurrence as a side effect of certain immunomodulatory drugs. A hypothesis has gained general acceptance that JC virus causes a primary infection in childhood and enters a latent state, after which immunosuppression allows viral reactivation leading to PML. Nonetheless, many important aspects of PML pathogenesis remain unclear, including the molecular bases of latency and reactivation, the site(s) of latency, the relationship of archetype and prototype virus and the mode of virus transmission within the body and between individuals. In this review, we will revisit these areas and examine what the available evidence suggests.

• Astrocyte-elevated gene-1 (AEG-1) induction by hypoxia and glucose deprivation in glioblastoma.

  Authors: Evan Noch, Markus Bookland, Kamel Khalili

  Cancer biology & therapy. 01/2011; 11(1):32-9.

  Glioblastomas continue to carry poor prognoses for patients despite advances in surgical, chemotherapeutic, and radiation regimens. One feature of glioblastoma associated with poor prognosis is theGlioblastomas continue to carry poor prognoses for patients despite advances in surgical, chemotherapeutic, and radiation regimens. One feature of glioblastoma associated with poor prognosis is the degree of hypoxia and expression levels of hypoxia-inducible factor-1 α (HIF-1α). HIF-1α expression allows metabolic adaptation to low oxygen availability, partly through upregulation of VEGF and increased tumor angiogenesis. Here, we demonstrate an induced level of astrocyte-elevated gene-1 (AEG-1) by hypoxia in glioblastoma cells. AEG-1 has the capacity to promote anchorage-independent growth and cooperates with Ha-ras in malignant transformation. In addition, AEG-1 was recently demonstrated to serve as an oncogene and can induce angiogenesis in glioblastoma. Results from in vitro studies show that hypoxic induction of AEG-1 is dependent on HIF-1α stabilization during hypoxia and that PI3K inhibition abrogates AEG-1 induction during hypoxia through loss of HIF-1α stability. Furthermore, we show that AEG-1 is induced by glucose deprivation and that prevention of intracellular reactive oxygen species (ROS) production prevents this induction. Additionally, AEG-1 knockdown results in increased ROS production and increased glucose deprivation-induced cytotoxicity. On the other hand, AEG-1 overexpression prevents ROS production and decreases glucose deprivation-induced cytotoxicity, indicating that AEG-1 induction is necessary for cells to survive this type of cell stress. These observations link AEG-1 overexpression in glioblastoma with hypoxia and glucose deprivation, and targeting these physiological pathways may lead to therapeutic advances in the treatment of glioblastoma in the future.

• Suppression of HIV-1 transcriptional elongation by a DING phosphatase.

  Authors: Nune Darbinian, Rebeccah Gomberg, Loriann Mullen, Samantha Garcia, Martyn K White, Kamel Khalili, Shohreh Amini

  Journal of cellular biochemistry. 01/2011; 112(1):225-32.

  HIV-1 gene transcription is controlled by the cooperation of viral and host factors which bind to specific DNA sequences within the viral promoter spanning the long terminal repeat (LTR). PreviouslyHIV-1 gene transcription is controlled by the cooperation of viral and host factors which bind to specific DNA sequences within the viral promoter spanning the long terminal repeat (LTR). Previously we showed that the St. John's Wort DING phosphatase, p27SJ, suppresses HIV-1 gene transcription by binding to the viral protein Tat and preventing its nuclear import. Here, we describe the inhibitory effect of p27SJ on the phosphorylation of the C-terminal domain (CTD) of RNA polymerase II (RNAPII). This inhibition leads to the suppression of the association of RNAPII with the LTR. Inhibition of binding of RNAPII to LTR by p27SJ resulted in the suppression of LTR transcription elongation and a decrease in LTR transcriptional activity. Another form of the St. John's Wort DING phosphatase, p38SJ, also suppressed binding of RNAPII to the LTR, reduced transcription elongation and was even more powerful than p27SJ in inhibiting the transcriptional activity of the LTR. Our data suggest a possible mechanism by which the p27SJ/p38SJ DING phosphatase can regulate HIV-1 LTR expression by inhibiting phosphorylation of the CTD of RNAPII and suppressing LTR transcription elongation.

• BAG3 expression in glioblastoma cells promotes accumulation of ubiquitinated clients in an Hsp70-dependent manner.

  Authors: Antonio Gentilella, Kamel Khalili

  The Journal of biological chemistry. 01/2011; 286(11):9205-15.

  Disposal of damaged proteins and protein aggregates is a prerequisite for the maintenance of cellular homeostasis and impairment of this disposal can lead to a broad range of pathological conditions,Disposal of damaged proteins and protein aggregates is a prerequisite for the maintenance of cellular homeostasis and impairment of this disposal can lead to a broad range of pathological conditions, most notably in brain-associated disorders including Parkinson and Alzheimer diseases, and cancer. In this respect, the Protein Quality Control (PQC) pathway plays a central role in the clearance of damaged proteins. The Hsc/Hsp70-co-chaperone BAG3 has been described as a new and critical component of the PQC in several cellular contexts. For example, the expression of BAG3 in the rodent brain correlates with the engagement of protein degradation machineries in response to proteotoxic stress. Nevertheless, little is known about the molecular events assisted by BAG3. Here we show that ectopic expression of BAG3 in glioblastoma cells leads to the activation of an HSF1-driven stress response, as attested by transcriptional activation of BAG3 and Hsp70. BAG3 overexpression determines an accumulation of ubiquitinated proteins and this event requires the N-terminal region, WW domain of BAG3 and the association of BAG3 with Hsp70. The ubiquitination mainly occurs on BAG3-client proteins and the inhibition of proteasomal activity results in a further accumulation of ubiquitinated clients. At the cellular level, overexpression of BAG3 in glioblastoma cell lines, but not in non-glial cells, results in a remarkable decrease in colony formation capacity and this effect is reverted when the binding of BAG3 to Hsp70 is impaired. These observations provide the first evidence for an involvement of BAG3 in the ubiquitination and turnover of its partners.

• Regulation of human neurotropic JC virus replication by alternative splicing factor SF2/ASF in glial cells.

  Authors: Ilker Kudret Sariyer, Kamel Khalili

  PloS one. 01/2011; 6(1):e14630.

  The human neurotropic virus, JC virus (JCV), is the etiologic agent of the fatal demyelinating disease of the central nervous system, Progressive Multifocal Leukoencephalopathy (PML) that is seenThe human neurotropic virus, JC virus (JCV), is the etiologic agent of the fatal demyelinating disease of the central nervous system, Progressive Multifocal Leukoencephalopathy (PML) that is seen primarily in immunodeficient individuals. Productive infection of JCV occurs only in glial cells, and this restriction is, to a great extent, due to the activation of the viral promoter that has cell type-specific characteristics. Earlier studies led to the hypothesis that glial-specific activation of the JCV promoter is mediated through positive and negative transcription factors that control reactivation of the JCV genome under normal physiological conditions and suppress its activation in non-glial cells. Using a variety of virological and molecular biological approaches, we demonstrate that the alternative splicing factor SF2/ASF has the capacity to exert a negative effect on transcription of the JCV promoter in glial cells through direct association with a specific DNA sequence within the viral enhancer/promoter region. Our results show that down-regulation of SF2/ASF in fetal and adult glial cells increases the level of JCV gene expression and its replication indicating that negative regulation of the JCV promoter by SF2/ASF may control reactivation of JCV replication in brain. Our results establish a new regulatory role for SF2/ASF in controlling gene expression at the transcriptional level.

• Regulation of the HIV-1 promoter by HIF-1α and Vpr proteins.

  Authors: Satish L Deshmane, Shohreh Amini, Satarupa Sen, Kamel Khalili, Bassel E Sawaya

  Virology journal. 01/2011; 8:477.

  We previously demonstrated the ability of HIV-1 Vpr protein to activate the oxidative stress pathway, thus leading to the induction of the hypoxia inducible factor 1 alpha (HIF-1α). Therefore, weWe previously demonstrated the ability of HIV-1 Vpr protein to activate the oxidative stress pathway, thus leading to the induction of the hypoxia inducible factor 1 alpha (HIF-1α). Therefore, we sought to examine the interplay between the two proteins and the impact of HIF-1α activation on HIV-1 transcription. Using transient transfection assays, we identified the optimal concentration of HIF-1α necessary for the activation of the HIV-1 promoter as well as the domain within HIF-1α responsible for this activation. Our findings indicated that activation of the HIV-1 LTR by Vpr is HIF-1α dependent. Furthermore, we showed that both Vpr and HIF-1α activate the HIV-1 promoter through the GC-rich binding domain within the LTR. Taken together, these data shed more light on the mechanisms used by Vpr to activate the HIV-1 promoter and placed HIF-1α as a major participant in this activation.

• Role for tumor necrosis factor-α in JC virus reactivation and progressive multifocal leukoencephalopathy.

  Authors: Hassen S Wollebo, Mahmut Safak, Luis Del Valle, Kamel Khalili, Martyn K White

  Journal of neuroimmunology. 12/2010; 233(1-2):46-53.

  JCV causes the CNS demyelinating disease progressive multifocal leukoencephalopathy (PML). After primary infection, JCV persists in a latent state, where viral protein expression and replication areJCV causes the CNS demyelinating disease progressive multifocal leukoencephalopathy (PML). After primary infection, JCV persists in a latent state, where viral protein expression and replication are not detectable. NF-κB and C/EBPβ regulate the JCV promoter via a control element, κB, suggesting proinflammatory cytokines may reactivate JCV to cause PML, e.g., in HIV-1/AIDS. Since HIV-1 induces cytokines in brain, including TNF-α, we examined a role for TNF-α in JCV regulation. TNF-α stimulated both early and late JCV transcription. Further, the κB element conferred TNF-α response to a heterologous promoter. Immunohistochemistry of HIV+/PML revealed robust labeling for TNF-α and TNFR-1. These data suggest TNF-α stimulation of κB may contribute to JCV reactivation in HIV+/PML.

• Role of Purα in the cellular response to ultraviolet-C radiation.

  Authors: Rafal Kaminski, Laurelle Cheeseboro, Shohreh Amini, Edward M Johnson, Martyn K White, Kamel Khalili, Armine Darbinyan

  Cell cycle (Georgetown, Tex.). 10/2010; 9(20):4164-73.

  Purα is a nucleic acid-binding protein with DNA-unwinding activity, which has recently been shown to have a role in the cellular response to DNA damage. We have investigated the function of Purα inPurα is a nucleic acid-binding protein with DNA-unwinding activity, which has recently been shown to have a role in the cellular response to DNA damage. We have investigated the function of Purα in Ultraviolet-C (UVC) radiation-induced DNA damage and nucleotide excision repair (NER). Mouse embryo fibroblasts from PURA(-/-) knockout mice, which lack Purα, showed enhanced sensitivity to UVC irradiation as assessed by assays for cell viability and clonogenicity compared to Purα positive control cultures. In reporter plasmid reactivation assays to measure the removal of DNA adducts induced in vitro by UVC, the Purα-negative cells were less efficient in DNA damage repair. Purα-negative cells were also more sensitive to UVC-induced DNA damage measured by Comet assay and showed a decreased ability to remove UVC-induced cyclobutane pyrimidine dimers. In wild-type mouse fibroblasts, expression of Purα is induced following S-phase checkpoint activation by UVC in a similar manner to the NER factor TFIIH. Moreover, co-immunoprecipitation experiments showed that Purα physically associates with TFIIH. Thus, Purα has a role in NER and the repair of UVC-induced DNA damage.

• BAG3 expression is sustained by FGF2 in neural progenitor cells and impacts cell proliferation.

  Authors: Antonio Gentilella, Kamel Khalili

  Cell cycle (Georgetown, Tex.). 10/2010; 9(20):4245-7.

• Could NSP5a3a be a target for head and neck cancer?

  Authors: Martyn K White, Kamel Khalili

  Oncotarget. 10/2010; 1(6):386.