Sprouty/Spred family proteins have been identified as negative regulators of growth factor-induced ERK/mitogen-activated protein (MAP) kinase activation. However, it has not been clarified whether these proteins regulate cytokine-induced ERK activity. We found that Spred-1 is highly expressed in interleukin-3 (IL-3)-dependent hematopoietic cell lines and bone marrow-derived mast cells. To investigate the roles of Spred-1 in hematopoiesis, we expressed wild-type Spred-1 and a dominant negative form of Spred-1, ⌬C-Spred, in IL-3-and stem cell factor (SCF)-dependent cell lines as well as hematopoietic progenitor cells from mouse bone marrow by retrovirus gene transfer. In IL-3-dependent Ba/F3 cells expressing c-kit, forced expression of Spred-1 resulted in a reduced proliferation rate and ERK activation in response to not only SCF but also IL-3. In contrast, ⌬C-Spred augmented IL-3-induced cell proliferation and ERK activation. Wild-type Spred-1 inhibited colony formation of bone marrow cells in the presence of cytokines, whereas ⌬C-Spred-1 expression enhanced colony formation. Augmentation of ERK activation and proliferation in response to IL-3 was also observed in Spred-1-deficient bone marrow-derived mast cells. These data suggest that Spred-1 negatively regulates hematopoiesis by suppressing not only SCFinduced but also IL-3-induced ERK activation.Receptor tyrosine kinases, such as stem cell factor (SCF) 1 receptor (c-kit), as well as cytokine receptors including interleukin (IL)-3 or erythropoietin (EPO) receptor activate the extracellular signal-regulated kinase (ERK) cascade. ERK activation is initiated by binding of Grb2 to the phosphorylated tyrosine residues of the receptor or phosphorylated adaptor molecules such as Shc, FRS-2, IRS-1/2, SHP-2, and Gab-1. The complex of Grb2 and SOS (son of sevenless) activates Ras by GTP loading. Ras-GTP recruits Raf1 to the plasma membrane (1, 2), which is then phosphorylated and activated by several, not well defined, kinases with complex regulatory mechanisms (3-5). Activated Raf then phosphorylates and activates the dual-specific kinase MEK, which phosphorylates and activates ERKs. In addition, the Ras-independent Raf1-ERK activation mechanism has been recently demonstrated, and members of the protein kinase C family of serine/threonine kinases have been implicated as potential activators of Raf (6).Mitogen-activated protein (MAP) kinases including ERKs play important roles in hematopoiesis. Most hematopoietic cytokines (hematopoietins) activate the JAK-STAT and Ras-ERK pathways, both being required for a satisfactory level of proliferation and differentiation of hematopoietic cells. For example, STAT5 activation is not sufficient for EPO-dependent growth of CTLL2 cells expressing EPO receptor, but additional activation of MAP kinases can support their cellular proliferation in response to EPO (7). MAP kinases have also been shown to play a critical role in megakaryopoiesis by c-mpl (8). However, little is known about how MAP kinase is regulated in hematopoietic cell...

We report here that loss of the Sprouty2 gene (also known as Spry2) in mice resulted in enteric nerve hyperplasia, which led to esophageal achalasia and intestinal pseudo-obstruction. Glial cell line-derived neurotrophic factor (GDNF) induced hyperactivation of ERK and Akt in enteric nerve cells. Anti-GDNF antibody administration corrected nerve hyperplasia in Sprouty2-deficient mice. We show Sprouty2 to be a negative regulator of GDNF for the neonatal development or survival of enteric nerve cells.

BackgroundRecent studies suggest that tonsilloliths are clinically related to halitosis and tonsillar abscess. Based on our empirical knowledge, tonsilloliths are relatively commonly encountered in daily clinical practice. It has been reported that the detection rate of tonsilloliths was under 24% in previous reports, although experience suggests otherwise. The purpose of the study was to evaluate the prevalence and characteristics of tonsilloliths using computed tomography (CT). In addition, the possible causes of low detection rates on panoramic radiographs were evaluated based on comparisons between CT images and panoramic radiographs in order to elucidate the limitations of visualizing the area around the palatine tonsils on panoramic radiographs.Methods482 pairs of CT images and panoramic radiographs were retrospectively assessed with respect to the presence and characteristics of tonsilloliths. In addition, the causes in cases of disagreement between the two modalities were analyzed.ResultsThe detection rate of tonsilloliths was 46.1% using CT scans, unlike previous reports. The characteristics of tonsillolith were dot-like figures with about 300-500 Hounsfield units within the palatine tonsil under the soft palate. The most common length of tonsilloliths was about 3 or 4 mm. As the subjects aged, the detection rate increased gradually. A significant difference in the tonsillolith detection rate was found between the over and under 40-year-old groups (p < 0.0001). However, the detection rate of tonsilloliths was only 7.3% on panoramic radiographs. A significant correlation was observed between the detection rate of tonsilloliths on panoramic radiographs and CT number (Spearman r = 0.429), size, (Spearman r = 0.318), and number of tonsilloliths (Spearman r = 0.333).ConclusionThe present results suggest that tonsilloliths are relatively more common than previously suggested. However, panoramic radiographs detect only a small percentage of palatine tonsilloliths. The low detection rates on panoramic radiographs might be related to the degree of calcification, size, and number of tonsilloliths.

Inflammation associates with insulin resistance, which dysregulates nutrient homeostasis and leads to diabetes. The suppressor of cytokine signaling 3 (SOCS3), which is induced by pro-inflammatory cytokines, such as TNFalpha and IL-6, has been implicated in inflammation-mediated insulin resistance in the liver and adipocytes. However, no genetic evidence has been provided for the involvement of SOCS3 on insulin resistance. Here, we generated hepatocyte-specific SOCS3-deficient (L-SOCS3 cKO) mice and examined insulin sensitivity. Being consistent with a previous idea, the loss of SOCS3 in the liver apparently improved insulin sensitivity. However, unexpectedly, L-SOCS3 cKO mice exhibited obesity and systemic insulin resistance with age. Insulin signaling was rather suppressed in muscles, suggesting that deletion of the SOCS3 gene in the liver modulates insulin sensitivity in other organs. Anti-inflammatory reagent, sodium salicylate, partial improved insulin resistance of aged L-SOCS3 cKO mice, suggesting that enhanced inflammatory status is associated with the phenotype of these mice. STAT3 was hyperactivated and acute-phase proteins were elevated in L-SOCS3 cKO mice liver, which were reduced by sodium salicylate treatment. We conclude that hepatic SOCS3 is a mediator of insulin resistance in the liver; however, lack of SOCS3 in the liver promotes systemic insulin resistance by mimicking chronic inflammation.

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