Activation of brain melanocortin 4 receptors (MC4Rs) leads to reduced food intake, increased energy expenditure, increased insulin sensitivity, and reduced linear growth. MC4R effects on energy expenditure and glucose metabolism are primarily mediated by the G protein Gsα in brain regions outside of the paraventricular nucleus of the hypothalamus (PVN). However, the G protein(s) that is involved in MC4R-mediated suppression of food intake and linear growth, which are believed to be regulated primarily though action in the PVN, is unknown. Here, we show that PVN-specific loss of Gqα and G11α, which stimulate PLC, leads to severe hyperphagic obesity, increased linear growth, and inactivation of the hypothalamic-pituitary-adrenal axis, without affecting energy expenditure or glucose metabolism. Moreover, we demonstrate that the ability of an MC4R agonist delivered to PVN to inhibit food intake is lost in mice lacking Gq/11α in the PVN but not in animals deficient for Gsα. The blood pressure response to the same MC4R agonist was only lost in animals lacking Gsα specifically in the PVN. Together, our results exemplify how different physiological effects of GPCRs may be mediated by different G proteins and identify a pathway for appetite regulation that could be selectively targeted by Gq/11α-biased MC4R agonists as a potential treatment for obesity.
Yong-Qi Li, Yogendra Shrestha, Mritunjay Pandey, Min Chen, Ahmed Kablan, Oksana Gavrilova, Stefan Offermanns, Lee S. Weinstein
Vascular oxidative injury accompanies many common conditions associated with hypertension. In the present study, we employed mouse models with excessive vascular production of ROS (tgsm/p22phox mice, which overexpress the NADPH oxidase subunit p22
Jing Wu, Mohamed A. Saleh, Annet Kirabo, Hana A. Itani, Kim Ramil C. Montaniel, Liang Xiao, Wei Chen, Raymond L. Mernaugh, Hua Cai, Kenneth E. Bernstein, Jörg J. Goronzy, Cornelia M. Weyand, John A. Curci, Natalia R. Barbaro, Heitor Moreno, Sean S. Davies, L. Jackson Roberts II, Meena S. Madhur, David G. Harrison
MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. The mechanisms that underlie MDM4 upregulation in cancer cells are largely unknown. Here, we have shown that this key oncogenic event mainly depends on a specific alternative splicing switch. We determined that while a nonsense-mediated, decay-targeted isoform of
Michael Dewaele, Tommaso Tabaglio, Karen Willekens, Marco Bezzi, Shun Xie Teo, Diana H.P. Low, Cheryl M. Koh, Florian Rambow, Mark Fiers, Aljosja Rogiers, Enrico Radaelli, Muthafar Al-Haddawi, Soo Yong Tan, Els Hermans, Frederic Amant, Hualong Yan, Manikandan Lakshmanan, Ratnacaram Chandrahas Koumar, Soon Thye Lim, Frederick A. Derheimer, Robert M. Campbell, Zahid Bonday, Vinay Tergaonkar, Mark Shackleton, Christine Blattner, Jean-Christophe Marine, Ernesto Guccione
The DNA methyltransferases DNMT3A and DNMT3B are primarily responsible for de novo methylation of specific cytosine residues in CpG dinucleotides during mammalian development. While loss-of-function mutations in DNMT3A are highly recurrent in acute myeloid leukemia (AML),
Christopher B. Cole, Angela M. Verdoni, Shamika Ketkar, Elizabeth R. Leight, David A. Russler-Germain, Tamara L. Lamprecht, Ryan T. Demeter, Vincent Magrini, Timothy J. Ley
Magnetic resonance–guided focused ultrasound (MRgFUS) facilitates noninvasive image-guided conformal thermal therapy of cancer. Yet in many scenarios, the sensitive tissues surrounding the tumor constrain the margins of ablation; therefore, augmentation of MRgFUS with chemotherapy may be required to destroy remaining tumor. Here, we used 64Cu-PET-CT, MRI, autoradiography, and fluorescence imaging to track the kinetics of long-circulating liposomes in immunocompetent mammary carcinoma–bearing FVB/n and BALB/c mice. We observed a 5-fold and 50-fold enhancement of liposome and drug concentration, respectively, within MRgFUS thermal ablation–treated tumors along with dense accumulation within the surrounding tissue rim. Ultrasound-enhanced drug accumulation was rapid and durable and greatly increased total tumor drug exposure over time. In addition, we found that the small molecule gadoteridol accumulates around and within ablated tissue. We further demonstrated that dilated vasculature, loss of vascular integrity resulting in extravasation of blood cells, stromal inflammation, and loss of cell-cell adhesion and tissue architecture all contribute to the enhanced accumulation of the liposomes and small molecule probe. The locally enhanced liposome accumulation was preserved even after a multiweek protocol of doxorubicin-loaded liposomes and partial ablation. Finally, by supplementing ablation with concurrent liposomal drug therapy, a complete and durable response was obtained using protocols for which a sub-mm rim of tumor remained after ablation.
Andrew W. Wong, Brett Z. Fite, Yu Liu, Azadeh Kheirolomoom, Jai W. Seo, Katherine D. Watson, Lisa M. Mahakian, Sarah M. Tam, Hua Zhang, Josquin Foiret, Alexander D. Borowsky, Katherine W. Ferrara
Increased sodium influx via incomplete inactivation of the major cardiac sodium channel NaV1.5 is correlated with an increased incidence of atrial fibrillation (AF) in humans. Here, we sought to determine whether increased sodium entry is sufficient to cause the structural and electrophysiological perturbations that are required to initiate and sustain AF. We used mice expressing a human NaV1.5 variant with a mutation in the anesthetic-binding site (F1759A-NaV1.5) and demonstrated that incomplete Na+ channel inactivation is sufficient to drive structural alterations, including atrial and ventricular enlargement, myofibril disarray, fibrosis and mitochondrial injury, and electrophysiological dysfunctions that together lead to spontaneous and prolonged episodes of AF in these mice. Using this model, we determined that the increase in a persistent sodium current causes heterogeneously prolonged action potential duration and rotors, as well as wave and wavelets in the atria, and thereby mimics mechanistic theories that have been proposed for AF in humans. Acute inhibition of the sodium-calcium exchanger, which targets the downstream effects of enhanced sodium entry, markedly reduced the burden of AF and ventricular arrhythmias in this model, suggesting a potential therapeutic approach for AF. Together, our results indicate that these mice will be important for assessing the cellular mechanisms and potential effectiveness of antiarrhythmic therapies.
Elaine Wan, Jeffrey Abrams, Richard L. Weinberg, Alexander N. Katchman, Joseph Bayne, Sergey I. Zakharov, Lin Yang, John P. Morrow, Hasan Garan, Steven O. Marx
The cover image shows ovarioles from a fly expressing a transgenic mutant of nucleoporin-107 (Nup107, red), which frequently led to collapsed nuclear envelopes, condensed nuclei (green), and increased apoptosis (cleaved caspase-3, blue). On page 4295, Weinberg-Shukron et al. identify a missense mutation in human NUP107 in a family with XX gonadal dysgenesis and demonstrate that the analogous mutation in Drosophila causes ovarian developmental defects.
JCI This Month is a digest of the research, reviews, and other features published each month.
In the mid-1800s, Rudolf Virchow noted the presence of surfeit inflammatory cells in many tumors. Roughly 50 years later, Paul Ehrlich postulated that the immune system both recognizes and protects against cancer. Since then, researchers have been trying to elucidate the relationship between cancer, inflammation, and the innate and adaptive immune systems, starting with the theory of immunosurveillance introduced by Lewis Thomas and further developed by Sir MacFarlane Burnet. We now know that tumor cells display antigens that are recognized by immune cells, but that anti-tumor immunity can be circumvented directly by tumor cells themselves via a variety of escape mechanisms. The goal of cancer immunotherapy is to mount an effective anti-tumor immune response by repairing, stimulating or, enhancing the immune system’s response to cancer cells. Reviews in this series detail progress in cancer immunoediting, immunosuppressive cells in the tumor microenvironment, cancer-associated inflammation, therapeutic cancer vaccines, genomic approaches in immunotherapy, adoptive transfer of genetically engineered T cells, and checkpoint blockade therapy.