Metabolic changes within the tumor microenvironment include increased glycolysis; however, it not clear if enhanced glycolytic activity is the result of tumorigenesis or an oncogenic-driving event. Using a 3-dimensional cell culture system (lrECM) to evaluate the role of aerobic glycolysis in breast cancer cells, Yasuhito Onodera, Jin-Min Nam, and Mina Bissell revealed that increased sugar uptake by mammary cells promotes oncogenesis, rather than being a cancer-induced metabolic change. Overexpression of glucose transporter 3 (GLUT3) in non-malignant human breast cells activated known oncogenic pathways, resulting in a loss of tissue polarity, and increased cell replication. In contrast, reduction of glucose uptake in malignant breast cancer cells restored tissue organization and suppressed oncogenic signaling. Furthermore, the authors revealed that glucose-dependent upregulation of EPAC/RAP1 and O-linked N-acetylglucosamine pathways drive cancer-associated phenotypes. In the accompanying image, non-malignant S1 cells (top left) and malignant T4-2 cells (top right) show no difference in organization when cultured in 2D; however, S1 cells cultured in lrECM (bottom left) exhibit a polarized structure, while T4-2 cells cultured in lrECM exhibit a disorganized structure as seen with staining for alpha-6 integrin (green), beta-actin (red) and DAPI (blue).
Maintaining T cell polyfunctionality
In order to protect the body from viruses and cancer, T cells must perform multiple functions, a feature that is often lost during chronic infection. Jonathan Schneck and colleagues examined the molecular mechanisms that maintain T cell polyfunctionality. They found that MAPK/ERK signaling was upregulated in polyfunctional T cells and that activation of this pathway was altered in response to different levels of antigen. Importantly, high levels of antigen increased levels of sprouty-2 (SPRY2), a negative regulator of MAPK/ERK signaling. High levels of SPRY2 were observed in HIV-specific T cells and inhibition of SPRY2 expression increased polyfunctional responses to HIV. These findings suggest that SPRY2 could be targeted to increase T cell polyfunctionality in the context of chronic viral infections.
Watch the video: http://www.youtube.com/watch?v=sqYJm7mg_5U
Read the article: http://www.jci.org/articles/view/70510
In the latest Conversations with Giants in Medicine, the JCI speaks with Thomas Südhof of Stanford University. In 2013, Dr. Südhof was a co-recipient of the Nobel Prize in Physiology or Medicine and the Albert Lasker Basic Medical Research Award for his contribution to the understanding of the molecular mechanisms of neurotransmission in synaptic signaling. The full interview between Ushma Neil and Thomas Südhof can be seen on the JCI website, along with all of the JCI‘s Conversations with Giants in Medicine.
PTEN hamartoma syndrome (PHTS) is a diverse syndrome that develops as the result of mutations in the gene encoding the tumor suppressor PTEN. Cataract formation is common in PHTS patients; however, it is not clear if cataract onset is directly a result of PTEN loss or a secondary effect. Caterina Sellitto and colleagues at Stony Brook University generated a mouse line with lens-specific deletion of Pten to evaluate the contribution of PTEN to cataract development. Lenses from mice lacking PTEN exhibited increased hydrostatic pressure and intracellular sodium concentrations, which led to swelling, cataract, and eye rupture. The authors determined that AKT activation was increased in the lenses of these mice, and pharmacological inhibition of AKT reduced lens pressure. This study demonstrates that PTEN directly regulates lens ion transport via AKT and provides an animal model to investigate PHTS-associated cataract development. The accompanying image shows a WT mouse (top) and a mouse with lens-specific Pten deletion (bottom) at 24 weeks. Cataracts are clearly visible in the mutant animal.
Protecting the kidney through ion channel inhibition
Damage to the glomerulus, which mediates the kidney’s filtering function, causes plasma protein to spill into the urine, a sign of kidney failure and cardiovascular disease. Calcium influx into the podocytes, the cells that form the filtration barrier of the glomerulus, is known to damage the glomerulus, but the ion channel that mediates this influx was unknown. In this episode, Anna Greka and colleagues discuss their recent work demonstrating that inhibition of the TRPC5 ion channel protects mice from kidney damage by preventing calcium influx into the podocytes, and blocks the cytoskeletal alterations in the podocytes that disrupts the filtration barrier in the glomerulus
Read the article: http://www.jci.org/articels/view/71165
Watch the video: http://www.youtube.com/watch?v=SMK4aPugL2s#t=36
Exploring long-term expression of theraputic transgenes
Results from early-phase clinical trials have indicated that recombinant adeno-associated viruses (rAAV) could potentially be used for gene therapy. In each trial, however, patients have developed T cell-mediated immune responses that may interfere with therapeutic gene expression. In this episode, Terence Flotte and Christian Mueller discuss their recent study investigating T cell responses to intramuscular injection of a rAAV encoding M-type α1-antitrypsin (AAT) in patients with AAT-deficiency. Their results demonstrate that AAT expression persists for up to 12 months and suggest that immunomodulation of T cell populations may not be necessary for long-term, rAAV-mediated transgene expression.
Read the article: http://www.jci.org/articles/view/70314
Watch the video: http://www.youtube.com/watchv=JiqkCaEzLlI&list=UUdSgoILd_nUqms9KYtD-Ojg
The kidney is responsible for retaining essential proteins and removing waste products from the blood stream. The kidney filter is maintained by an intricate structure formed by the actin-rich foot process of podocytes that surround the glomerular capillaries. Injury to the kidney promotes a signaling cascade that results in cytoskeletal remodeling, effacement of podocyte foot processes, and loss of the filter function, which can ultimately result in kidney failure. Thomas Schaldecker, Sookyung Kim, Constantine Tarabanis and colleagues at Massachusetts General Hospital discovered that mice lacking the ion channel TRPC5 were protected from podocyte effacement and loss of the kidney filtration barrier following kidney injury. Using live imaging, the authors found that in the absence of TRPC5, podocytes were protected from cytoskeletal remodeling in response to injury, thereby keeping the filter in tact. Furthermore, the authors demonstrated that pharmacological inhibition of TRPC5 protects animals from protein loss in the urine following kidney injury. This study indicates that activation of ion channel TRPC5 following kidney injury promotes loss of kidney filter function, and inhibition of this ion channel may have therapeutic potential. The accompanying indexed color image of a podocyte reveals intricate cytoskeletal structures using Life-Act technology. This image highlights the importance of the podocyte actin cytoskeleton to maintain an intact kidney filter barrier.
Patients suffering from myasthenia gravis (MG) have debilitating muscle weakness and fatigue. MG is the result of neuromuscular junction (NMJ) dysfunction and is frequently associated with the presence of autoantibodies that target the acetylcholine receptor (AChR) or the kinase MuSK, which are critical for NMJ formation. Subsets of MG patients do not produce autoantibodies against either AChR or MuSK and little is know about how MG develops in these individuals. Recently, autoantibodies against the low-density lipoprotein receptor-related protein 4 (LRP4) were identified in a cohort of three patients with MG. To determine if LRP4 autoantibodies contribute to MG, Chengyong Shen, Yisheng Lu, Bin Zhang, and colleagues from Georgia Regents University developed a mouse model of LRP4 autoantibody-induced MG. Immunization of mice with the extracellular domain of LRP4 induced the production of anti-LRP4 antibodies and MG-like symptoms. Furthermore, transfer of anti-LRP4 sera into mice also resulted in MG phenotypes. NMJs from these mice were fragmented and not fully formed. This study demonstrates that LRP4 antibodies promote MG, and that LRP4 is required to maintain NMJ function. The companion image depicts the NMJ. Neurofilaments are green, AchRs are red, and nuclei are stained blue. These structures are disrupted in MG.
The ability of the immune system to fend off specific pathogens following immunization depends the generation high-affinity antibody producing plasma cells (PCs) and long-lived memory B cells. Both PCs and B cells differentiate in germinal centers (GCs) within lymphoid tissue. Many B cell malignancies, including lymphoma, are the result of GC dysfunction; however the factors that regulate the GC response are poorly understood. Given that the histone H3 lysine 27 methyltransferase enhancer of zeste homolog 2 (EZH2) is highly expressed in human GC B cells, Marieta Caganova and colleagues from the Italian Foundation for Cancer Research evaluated the contribution of EZH2 to the maintenance of GC function. Lack of EZH2 in mouse B cells reduced the number of B cells in GCs, which led to poor antibody responses and fewer memory B cells. Furthermore, the absence of EZH2 increased apoptosis and sensitivity to genotoxic damage. GC-derived Non-Hodgkin lymphoma is associated with gain of function mutations in EZH2, and inhibition of EZH2 in NHL cells impaired growth. These data indicate that EZH2 function to maintain GC responses. The accompanying micrograph shows EZH2 expression (brown) in germinal centers of reactive lymph nodes.
Regulating immune activation by necrotic cells
In order to mount an effective immune response, T cells must be primed with the appropriate antigens to help them recognize malignant or pathogen-infected cells. Tim Greten and colleagues examined how necrotic cell death influences T cell cross-priming. Here they report on a molecular mechanism that blocks antigen cross-presentation by necrotic cells. Moreover, they found that this mechanism could be circumvented to promote immunogenicity of tumor cells.
Read the article: http://www.jci.org/articles/view/65698
Watch the video: http://www.youtube.com/watch?v=XnBtWCrSbjw