Proteinopathies are characterized by the accumulation of misfolded proteins, which ultimately interfere with normal cell function. While neurological diseases, such as Huntington disease and Alzheimer disease, are well-characterized proteinopathies, cardiac diseases have recently been associated with alterations in proteostasis. In this issue of the JCI, Fang and colleagues demonstrate that mice with cardiac-specific deficiency of the co-chaperone protein BCL2-associated athanogene 3 (BAG3) develop dilated cardiomyopathy that is associated with a destabilization of small HSPs as the result of a disrupted interaction between BAG3 and HSP70. Together, the results of this study suggest that strategies to upregulate BAG3 during cardiac dysfunction may be beneficial.
Wataru Mizushima, Junichi Sadoshima
Coronary revascularization is an effective means of treating ischemic heart disease; however, current therapeutic revascularization strategies are limited to large caliber vessels. Because the mammalian heart scars following cardiac injury, recent work showing that cardiac fibroblasts can transdifferentiate into new coronary endothelium raises a new and exciting approach to promoting endogenous revascularization following cardiac injury. In this issue of the JCI, He et al. report on their employment of a battery of lineage-tracing tools to address the developmental origins of fibroblasts that give rise to new endothelial cells. Surprisingly, cardiac fibroblasts did not appear to contribute appreciably to regeneration of cardiac endothelium. Instead, cardiac endothelial cells were likely to proliferate and generate new endothelium following injury. As these conclusions diverge from prior findings, additional work will be required to understand the sources that generate cardiac endothelium in new blood vessels after injury. Clarification of the origins of coronary endothelial cells during cardiac repair is essential for identifying improved approaches to revascularizing damaged myocardium in patients with ischemic heart disease.
Ravi Karra, Agoston O. Walter, Sean M. Wu
Overconsumption of fructose and other sugars has been linked to nonalcoholic fatty liver disease (NAFLD); however, the sugar-associated effects that lead to disease are poorly defined. In this issue of the JCI, Zhang and colleagues show that the carbohydrate response element–binding protein (ChREBP) coordinates an adaptive response to a high-fructose diet in mice and that loss of this transcription factor leads to hepatic inflammation and early signs of fibrosis. Intriguingly, ChREBP-dependent effects were due to an exaggerated activation of the proapoptotic arms of the endoplasmic reticulum stress response that is probably secondary to inappropriate derepression of cholesterol biosynthesis. These findings suggest that a previously unknown link exists between ChREBP and the regulation of cholesterol synthesis that affects liver injury.
Angela M. Hall, Brian N. Finck
While antiretroviral therapy (ART) can reduce HIV-1 to undetectable levels, the virus generally reappears if treatment is stopped. Resurgence of the virus is due to the reactivation of T cells harboring latent integrated provirus, and recent studies indicate that proliferation of these latently infected cells helps maintain the HIV-1 reservoir. In this issue of the JCI, Lee et al. evaluated CD4+ T cell subsets to determine whether certain populations are more likely to harbor full-length, replication-competent provirus. The authors identified an enrichment of clonally expanded Th1 cells containing intact HIV-1 proviruses, suggesting that this polarized subset contributes to the persistence of the reservoir. Strategies to target these provirus-harboring cells need to be considered for future therapies aimed toward HIV-1 cure.
Kyungyoon J. Kwon, Robert F. Siliciano
WNT proteins drive the development and maintenance of many tissues, including bone. It is less clear which of the many WNT proteins act on bone or where these WNTs act in the skeleton; however, loss-of-function mutations in WNT1 cause bone fragility in children and adults. In this issue of the JCI, Joeng and colleagues demonstrate that bone formation is under the control of WNT1 produced by osteocytes, the cells that reside deep in the bone matrix and form dendritic networks. The implication of WNT1 in the control of bone formation identifies a potential new target for the treatment of low bone mass disorders, such as osteoporosis.
Osteoclasts are the cells responsible for bone resorption, a process that is essential for the maintenance of healthy bones. Bone diseases, such as osteoporosis, which are characterized by high rates of bone resorption and loss of bone mass, may benefit from treatments that inhibit osteoclast formation and/or function. The RANKL/RANK pathway is critical for both osteoclast formation and function, and these effects are thought to be mediated by the transcription factor nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). In this issue of the
Diabetes mellitus is associated with an increased risk for cardiovascular disease, but the link between hyperglycemia and atherothrombotic disease is not completely understood. Patients with diabetes often show hyporesponsiveness to antiplatelet therapies, and it has been suggested that hyperreactive reticulated platelets underlie this altered therapeutic response. In this issue of the
Robert H. Lee, Wolfgang Bergmeier
The spermatogenesis/oogenesis helix-loop-helix (SOHLH) proteins SOHLH1 and SOHLH2 play important roles in male and female reproduction. Although previous studies indicate that these transcriptional regulators are expressed in and have in vivo roles in postnatal ovaries, their expression and function in the embryonic ovary remain largely unknown. Because oocyte differentiation is tightly coupled with the onset of meiosis, it is of significant interest to determine how early oocyte transcription factors regulate these two processes. In this issue of the
T. Rajendra Kumar
Observed deficits in protein phosphatase 2A (PP2A) function in a variety of human cancers have stimulated drug discovery efforts aimed at restoring PP2A function to inhibit tumor growth. Work published by Sangodkar et al. in this issue of the
Patients who present with unique immunological phenotypes provide an opportunity to better understand defect-driving mutations. In this issue of the
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