Current Molecular Medicine - Volume 13, Issue 7, 2013

The basic Helix-Loop-Helix/PER-ARNT-SIM (bHLH-PAS) domain family of transcription factors mediates cellular responses to a variety of internal and external stimuli. As functional transcription factors, these proteins act as bHLH-PAS heterodimers and can be further sub-classified into sensory/activated subunits and regulatory or ARNT-like proteins. This class of proteins act as master regulators of the bHLHPAS superfamily of transcription factors that mediate circadian rhythm gene programs, innate and adaptive immune responses, oxygen-sensing mechanisms and compensate for deleterious environmental exposures. Some contribute to the etiology of human pathologies including cancer because of their effects on cell growth and metabolism. We will review the canonical roles of ARNT and ARNT-like proteins with an emphasis on coactivator selectivity and recruitment. We will also discuss recent advances in our understanding of noncanonical DNA-binding independent or off-target roles of ARNT that are uncoupled from its classic heterodimeric bHLH-PAS binding partners. Understanding the DNA binding-independent functions of ARNT may identify novel therapeutic options for the treatment of a large spectrum of disease states.

Background: Nuclear Hormone Receptors (NHR) are, as the name implies, receptors located in the cell nucleus that have transcription modulating characteristics. Activated non-steroidal lipophilic ligands bind these receptors resulting in dimerisation of the ligands, DNA-binding and transcriptional regulation of target proteins that influence especially cell differentiation, metabolic homeostasis and embryogenesis. Methods: This review is based on publications derived from PubMed based pursuit of scientific literature in conjunction with the authors' experience. Results: Here, a summary of NHR family members (RXR, PPAR, VDR, TR) first in respect to known general aspects such as ligands, binding domains, signalling mechanism and second focussing especially their influence on female reproduction is offered. Furthermore, crosstalk with other prominent signalling proteins important to trophoblast function [signal transducer and activator of transcription (STAT), mitogen-activated protein kinase (MAPK), nuclear factor 'kappa-light-chain-enhancer' of activated B-cells (NFκB), Akt/ phosphaidyl-3-kinase (PI3K), and Wnt, are described. Conclusion: Considering their attributes, it is not surprising that NHR family members play a central role in female reproduction by targeting cell differentiation, metabolic homeostasis and embryogenesis. However, it seems that crosstalk depends on stage of trophoblast differentiation.

Adoptive cell therapy has shown impressive efficacy to combat cancer in early phase clinical trials, in particular when T cells engineered to specifically target tumor cells were applied. The patient's T cells are genetically equipped with a chimeric antigen receptor (CAR) which allows them to be redirected in a predefined manner towards virtually any target; by using an antibody-derived domain for binding, CAR T cells can be redirected in a major histocompatibility complex (MHC) dependent and independent fashion. The CAR also provides the stimuli required to induce and maintain T cell activation. Recent clinical data sustain the notion that strong costimulation in conjunction with the primary activation signal is crucial for lasting therapeutic efficacy of CAR T cells. However, costimulation is a double-edged sword and the impact of the individual costimuli to optimize T cell activation is still under debate; some general rules are emerging. The review summarizes how costimulation modulates, improves and prolongs the redirected anti-tumor T cell response and how the same costimulatory signals may contribute to unintended side effects including "cytokine storm" and T cell repression. Upcoming strategies to break the activation/repression circle by using CAR's with modified costimulatory signals are also discussed.

IκB kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1) are two non-canonical IKKs which are involved in interferon regulatory factor (IRF) as well as nuclear factor kappaB (NF-κB) signaling cascades. Both kinases have already been linked to the pathophysiology of several diseases and therefore been suggested as potential promising targets for the development of therapeutic drugs. In this review, we summarize the roles of IKKε and TBK1 in different diseases and outline therapeutic options for modulation of these kinases.

Proline-directed protein phosphorylation (pSer/Thr-Pro), a central signaling mechanism in diverse cellular processes in physiology and disease, has been proposed to be subject to further cis-trans conformational regulation by the unique prolyl isomerase Pin1. Until recently, no tool is available to directly detect the cis-trans conformation of Pin1-catalyzed cis-trans conformational changes in vivo. We have developed novel peptide chemistry that enables to generate the first antibodies that can distinguish cis from trans pThr231-Pro conformation in tau (p-tau). Using these conformation-specific antibodies, we have discovered that cis, but not trans, p-tau appears early in mild cognitive impairment (MCI) neurons and further accumulates in neurofibrillary degenerated neurons as Alzheimer's disease (AD) progresses, localizing to the dystrophic neurites, an early hallmark change that correlates with synaptic and cognitive deficits. Unlike trans p-tau, the cis not only cannot promote microtubule assembly, but also is more resistant to dephosphorylation and degradation, and prone to aggregation. Pin1 accelerates cis to trans conversion to prevent the accumulation of the pathogenic cis p-tau conformation in AD, providing the first structural evidence for how Pin1 protects against AD. These findings develop the first tool to directly detect cis-trans prolyl isomerization, especially after phosphorylation and uncover cis p-tau as the very early pathogenic conformation leading to tau pathology and memory loss in AD. These results also suggest novel conformation-specific diagnoses and therapies for AD and likely others.

Inflammatory bowel disease (IBD) is a group of inflammatory disorders in the small and large intestines. Several studies have proved that persistent and disregulated host/microbial interactions are required for the development of IBD. It is well known that chronic IBD is strongly associated with an increased risk of developing colorectal cancer by 0.5-1% annually, 8-10 years after the initial diagnosis. To detect the tiny dysplasia or early stage of cancer in chronic IBD patients, a tremendous amount of effort is currently directed for improving colonoscopic technology and noninvasive serological marker development. However, there is only a limited amount of data available to understand the exact mechanism of how long term chronic colitis is connected to the development of colorectal tumors. Recently, our group has identified significantly increased expression of chitinase 3-like 1 (CHI3L1) molecule in non-dysplastic mucosa from patients with IBD and remote dysplasia/cancer, compared to patients with IBD without dysplasia or healthy controls. CHI3L1 seems to contribute to the proliferation, migration, and neoplastic progression of colonic epithelial cells (CECs) under inflammatory conditions. Furthermore, the TLR4-mediated intracellular signaling cascade is likely to interact with CHI3L1 signaling in CECs. In this review article, we have concisely summarized the cellular and molecular mechanisms underlining the development of IBD and colitis-associated cancer, with particular focus on the TLR4- and CHI3L1-signaling pathways in CECs.

Despite significant research since it was discovered more than 50 years ago, respiratory syncytial virus (RSV) continues to be the leading agent causing infant hospitalization and respiratory distress worldwide. Although RSV normally does not cause mortality, this virus is recognized as a major public health and economic burden around the globe. RSV can modulate host immunity leading to an inflammatory response that produces lung damage and virus dissemination in the host airways. Remarkably, infection with the virus elicits poor immunity that in most cases fails to protect against subsequent exposures. Here, we review advances made on the understanding of the lifecycle of the virus, some of the molecular mechanisms it has evolved to cause pathology and ineffective immunity during infection. Hopefully, ongoing research will contribute to developing new drugs and candidate vaccines that will decrease the health burden caused by this virus.

Pancreatic cancer remains one of the deadliest of all cancers despite aggressive surgical treatment combined with adjuvant radiotherapy and chemotherapy. Chemoresistance and radioresistance are the principal causes of failure of pancreatic cancer patients to respond to therapy. Conditionally replicationcompetent adenovirus (CRCA)-based cancer gene therapy is an innovative strategy for treating cancers displaying inherent resistance to treatment. Limitations of current adenovirus (Ad)-based gene therapies for malignant tumors include lack of cancer-specificity, and effective and targeted delivery. To remedy this situation, CRCAs have been designed that express E1A, necessary for Ad replication, under the control of a cancer-specific progression elevated gene-3 promoter (PEG-Prom) with concomitant expression of an immunomodulatory cytokine, such as mda-7/IL-24 or interferon-γ (IFN-γ), under the control of a ubiquitous and strong cytomegalovirus promoter (CMV-Prom) from the E3 region. These bipartite CRCAs, when armed with a transgene, are called cancer terminator viruses (CTVs), i.e., Ad.PEG-E1A-CMV-mda-7 (CTV-M7) and Ad.PEG-E1A-CMV-IFN-γ (CTV-γ), because of their universal effectiveness in cancer treatment irrespective of p53/pRb/p16 or other genetic alterations in tumor cells. In addition to their selective oncolytic effects in tumor cells, the potent ‘bystander antitumor’ properties of MDA-7/IL-24 and IFN-γ embody the CTVs with expanded treatment properties for both primary and distant cancers. Pancreatic cancer cells display a “translational block” of mda-7/IL-24 mRNA, limiting production of MDA-7/IL-24 protein and cancer-specific apoptosis. Specific chemopreventive agents abrogate this “translational block” resulting in pancreatic cancer-specific killing. This novel chemoprevention gene therapy (CGT) strategy holds promise for both prevention and treatment of pancreatic cancers where all other strategies have proven ineffective.

Spinal muscular atrophy (SMA) is caused by mutations that reduce the level of the survival motor neuron protein (SMN) resulting in death of alpha-motor neurons, yet it is unclear why these cells are preferentially affected by a reduction in this ubiquitously-expressed protein. In mouse models of SMA, one of the earliest events detected is defects at the neuromuscular junction (NMJ). Although NMJs are established at a normal frequency, there are structural as well as functional perturbations and a lack of maturation of the primitive synapse. These early defects are followed by loss of the NMJ, denervation of the muscle and onset of muscle atrophy. In this review, we discuss our current understanding of the contribution of NMJ dysfunction in SMA disease pathogenesis, and also provide an overview of therapies currently under preclinical and clinical development for treatment of SMA.

Most drug targets are cellular proteins that selectively interact with chemicals administered to treat diseases. Chemical proteomics, as an interdisciplinary technology that integrates synthetic and analytic chemistry, biochemistry and cell biology, has recently emerged as a powerful platform to specifically enrich and comprehensively profile drug-binding proteins, and thus has been extensively applied in the identification of drug targets. In addition, chemical proteomics can also provide information for researchers to understand the poly-pharmacological activities of the pharmaceutical compounds, and thus help in maximizing the efficacy and minimizing the side effects of the drugs. In this manuscript, we summarized several popular approaches of chemical proteomics by illustrating their essential features in drug target-fishing through specific profiling of drug-protein interaction. Alternative technologies for target identification were also discussed.

Prolonged existence of helminth parasites in their mammalian hosts has led to the establishment of a very particular immunological microenvironment that supports the fitness of both the pathogen and the host. The modern way of living in developed societies has interrupted this tight relationship by almost completely removing helminths from the human population. It is believed that, as a consequence of this process, a rapid increase in the incidence of asthma and other inflammatory disorders has occurred. Data derived from experimental models clearly show that worms and their products can ameliorate asthma-like disease in mice. This review will concentrate on the effects of helminth-driven regulatory mechanisms on the function of eosinophils and neutrophils in experimental asthma. Eosinophils and neutrophils are major effector cells driving pathology in the lung, therefore learning how to control their exacerbated activation in asthma might aid in creating much needed novel therapeutics to combat this common inflammatory disorder.

U1 snRNP (U1 small nuclear ribonucleoprotein) is a well-characterized splicing factor. Besides, when U1 snRNP binds close to a putative polyadenylation site, mostly located in introns, it prevents premature cleavage and polyadenylation and controls the length of most cellular mRNAs. On the other hand, U1 snRNP binding close to the 3´-end of some mRNAs, inhibits polyadenylation and, therefore, gene expression. The inhibition of polyadenylation by U1 snRNP is the basis of U1i (U1 snRNP-based inhibition), a technique used to inhibit gene expression. U1i consists of the expression of a U1 snRNP modified to interact with a target mRNA and inhibit target gene expression. U1i has been used to inhibit the expression of reporter or endogenous genes both in tissue culture and in animal models. Furthermore, combination of U1i and RNA interference (RNAi) results in synergistic increased inhibitions which allow the dose of inhibitors to be decreased whilst at the same time obtaining good inhibitions with fewer unwanted secondary effects. The combination of RNAi and U1i is of special interest for antiviral therapy, as a functional decrease of the expression of replicative viral RNAs may require high inhibition and the combination of two or more inhibitors should decrease the possibility of escape mutants resistant to treatment. In fact, a therapy with U1i combined with RNAi is currently being developed for the treatment of HBV infections. We believe that this review will clarify the hallmarks of U1i technology and will encourage many laboratories to use U1i for functional studies and therapeutic applications.

Organ transplantation is an increasingly used medical procedure for treating otherwise fatal endstage organ diseases with 107,000 transplants performed worldwide in 2010. Newly developed anti-rejection drugs greatly helped to prolong long-term survival of both the individual and the transplanted organ, and they facilitate the diffusion of organ transplantation. Presently, 5-year patient survival rates are around 90% after kidney transplant and 70% after liver transplant. However, the prolonged chronic use of immunosuppressive drugs is well known to increase the risks of opportunistic diseases, particularly infections and virus-related malignancies. Although transplant recipients experience a nearly 2-fold elevated risk for all types of de-novo cancers, persistent infections with oncogenic viruses – such as Kaposi sarcoma herpes virus, high-risk human papillomaviruses, and Epstein-Barr virus – are associated with up to 100-fold increased cancer risks. This review, focusing on kidney and liver transplants, highlights updated evidences linking iatrogenic immunosuppression, persistent infections with oncogenic viruses and cancer risk. The implicit capacity of oncogenic viruses to immortalise infected cells by disrupting the cell-cycle control can lead, in a setting of induced lowered immune surveillance, to tumorigenesis and this ability is thought to closely correlate with cumulative exposure to immunosuppressive drugs. Mechanisms underlying the relationship between viral infections, immunosuppressive drugs and the risk of skin cancers, post-transplant lymphoproliferative disorders, Kaposi sarcoma, cervical and other ano-genital cancers are reviewed in details.