A novel circulation phosphaturic hormone is postulated to regulate systemic phosphate homeostasis. Two new studies reveal that the phosphaturic factor FGF-23 is increased in hypophosphatemic subjects with McCune-Albright syndrome and that secreted frizzled-related protein-4 (sFRP-4), a factor produced by tumors derived from subjects with tumor-induced osteomalacia, also has phosphaturic activity. It remains to be established whether FGF-23 and sFRP-4 represent two distinct phosphatonins or are somehow integrated in a novel phosphate-regulating bone-kidney axis.
L. Darryl Quarles
CD1d, a nonclassical MHC class I–like molecule, is prominently expressed on intestinal epithelial cells and is thought to function in the regulation of intestinal intraepithelial lymphocyte activity. Hsp110, an abundant heat shock protein present in essentially all mammalian tissues, has now been shown to upregulate CD1d expression in colonic tissue culture cell lines. Might this abundant chaperone serve an autocrine function in the regulation of CD1d expression?
Christopher V. Nicchitta
Mammals coexist in an overall symbiotic relationship with a complex array of commensal bacterial flora that colonizes the gastrointestinal tract. These intestinal bacteria interface with cells of the mucosal immune system, including DCs. Here we discuss mechanisms of interaction between intestinal bacteria and DCs and the role of localized gastrointestinal immune responses.
Holm H. Uhlig, Fiona Powrie
It has long been noted that while patients with familial hypertrophic cardiomyopathy due to cardiac troponin T (cTnT) mutations often suffer sudden cardiac death, they do not develop significant ventricular hypertrophy, suggesting that a distinct cellular mechanism apart from alterations in myocardial contractility is responsible. A new study has revealed that a single missense mutation in cTnT causes a striking disruption to energy metabolism, leading to cardiomyopathy.
Ketty Schwartz, Jean-Jacques Mercadier
A new study demonstrates that angiotensin-induced hypertension results in a marked decrease in expression of the β subunit of the BK channel, suggesting a role for this critical subunit in the regulation of vascular tone.
Michael Kotlikoff, Ian Hall
Bacillus anthracis, the causative agent of anthrax, is believed to induce disease and death in humans in an endotoxic shock–like manner. A comprehensive study of the effects of anthrax toxin in mice demonstrates that toxin-induced death is mediated not by cytokine release, as previously thought, but by hypoxia-induced liver failure. The study strongly suggests that the therapies developed for treatment of cytokine-mediated septic shock will not be appropriate for the treatment of anthrax.
Alice S. Prince
In an unusual paradox, asthmatics who are chronically treated with bronchodilating β-agonists sometimes experience a worsening of their condition. A new study describes one possible mechanism and reveals a potential new therapeutic target in the treatment of asthma.
Stephanie A. Shore, Jeffrey M. Drazen
Thyroid hormones are critical for differentiation, growth, and metabolism. A new study investigating the biological role of the TH receptor TR-β has demonstrated that DNA binding is critical for most of its functions, but also suggests that novel mechanisms independent of DNA binding may contribute to regulation of auditory function by TR-β.
Mitchell A. Lazar
The cell-surface associated molecule Cripto is overexpressed in a wide range of epithelial cancers, yet little is known about potential mechanisms by which Cripto expression might enhance tumorigenesis. A new study reveals that binding of Cripto to the TGF-β ligand Activin B can block Activin B–mediated suppression of cell proliferation. Furthermore, this study also demonstrates that antibody blockade of Cripto function may prove useful in the inhibition of tumorigenesis.
Michael M. Shen
Hepatitis delta virus (HDV) is a cause of acute and chronic liver disease for which no effective therapy is currently available. Previous research has demonstrated that prenylation of the large HDV antigen is essential for viral assembly. A new report describes a novel small animal model for HDV replication and demonstrates that prenylation inhibitors are highly effective at clearing viremia and thus have potential relevance for the treatment of chronic delta hepatitis.
Theo Heller, Jay H. Hoofnagle
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