Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia (ATL). HTLV-1 bZIP factor (HBZ), the viral gene transcribed from the antisense strand, is consistently ...expressed in ATL cells and promotes their proliferation. In this study, we found that a Wnt pathway-related protein, disheveled-associating protein with a high frequency of leucine residues (DAPLE), interacts with both HTLV-1 Tax and HBZ. In the presence of DAPLE, Tax activated canonical Wnt signaling. Conversely, HBZ markedly suppressed canonical Wnt activation induced by either Tax/DAPLE or β-catenin. As a mechanism of HBZ-mediated Wnt suppression, we found that HBZ targets lymphoid enhancer-binding factor 1, one of the key transcription factors of the pathway, and impairs its DNA-binding ability. We also observed that the canonical Wnt pathway was not activated in HTLV-1-infected cells, whereas the representative of noncanonical Wnt ligand, Wnt5a, which antagonizes canonical Wnt signaling, was overexpressed. HBZ was able to induce Wnt5a transcription by enhancing its promoter activity through the TGF-β pathway. Importantly, knocking down of Wnt5a in ATL cells repressed cellular proliferation and migration. Our results implicate novel roles of HBZ in ATL leukemogenesis through dysregulation of both the canonical and noncanonical Wnt pathways.
Casein kinase I (CKI) was recently reported as a positive regulator of Wnt signaling in vertebrates and Caenorhabditis elegans. To elucidate the function of Drosophila CKI in the wingless (Wg) ...pathway, we have disrupted its function by double‐stranded RNA‐mediated interference (RNAi). While previous findings were mainly based on CKI overexpression, this is the first convincing loss‐of‐function analysis of CKI. Surprisingly, CKIα‐ or CKIϵ‐RNAi markedly elevated the Armadillo (Arm) protein levels in Drosophila Schneider S2R+ cells, without affecting its mRNA levels. Pulse–chase analysis showed that CKI‐RNAi stabilizes Arm protein. Moreover, Drosophila embryos injected with CKIα double‐stranded RNA showed a naked cuticle phenotype, which is associated with activation of Wg signaling. These results indicate that CKI functions as a negative regulator of Wg/Arm signaling. Overexpression of CKIα induced hyper‐phosphorylation of both Arm and Dishevelled in S2R+ cells and, conversely, CKIα‐RNAi reduced the amount of hyper‐modified forms. His‐tagged Arm was phosphorylated by CKIα in vitro on a set of serine and threonine residues that are also phosphorylated by Zeste‐white 3. Thus, we propose that CKI phosphorylates Arm and stimulates its degradation.
Wingless (Wg) is an important signaling molecule in the development of Drosophila, but little is known about its signal transduction pathway. Genetic evidence indicates that another segment polarity ...gene, dishevelled (dsh) is required for Wg signaling. We have recently developed a cell culture system for Wg protein activity, and using this in vitro system as well as intact Drosophila embryos, we have analyzed biochemical changes in the Dsh protein as a consequence of Wg signaling. We find that Dsh is a phosphoprotein, normally present in the cytoplasm. Wg signaling generates a hyperphosphorylated form of Dsh, which is associated with a membrane fraction. Overexpressed Dsh becomes hyperphosphorylated in the absence of extracellular Wg and increases levels of the Armadillo protein, thereby mimicking the Wg signal. A deletional analysis of Dsh identifies several conserved domains essential for activity, among which is a so-called GLGF/DHR motif. We conclude that dsh, a highly conserved gene, is not merely a permissive factor in Wg signaling but encodes a novel signal transduction molecule, which may function between the Wg receptor and more downstream signaling molecules.
To examine the modulation of non-reciprocal group I (Ib) inhibition during tonic contraction of antagonist muscles in patients with spasticity vs normal subjects.
The authors studied 10 patients with ...spastic paraplegia due to cervical compression myelopathy and 16 age-matched normal subjects. Ib inhibition to soleus motoneurons was recorded as the change in size of the H-reflex of the soleus, evoked by conditioning stimulus to the nerve innervating the medial gastrocnemius muscle. The extent of inhibition was studied at rest and during tonic contraction of the pretibial muscles of variable strength.
In the resting state, the extent of inhibition in the patients did not differ from normal controls. During antagonist contraction, the extent of inhibition increased both in the normal subjects and patients. The increment was smaller in the patients, especially in those with severe spastic gait. The smaller increment in the inhibition was correlated with the time required to walk 10 m in the patients.
The authors observed a lack of modulation of Ib inhibition during tonic antagonist contraction in patients with spasticity, especially those with gait disturbance. Disturbed central modulation of non-reciprocal (Ib) interneurons may be responsible for spasticity.
Abstract
Enteral and parenteral nutrition is primarily indicated in patients that lack adequate oral intake to support their metabolic needs. Percutaneous endoscopic gastrostomy (PEG) has become the ...preferred procedure of choice. With the increasing prevalence of obesity in the USA, there is a need for special interventions for PEG tube placements in overweight and obese patients. Some challenges that frequently arise with obese patients include sub-optimal transillumination, insufficient abdominal landmarks and inability to estimate the abdominal and gastric walls. We present a case of a patient with persistent dysphagia requiring enteral nutrition with an unconventional placement of a PEG tube given patient’s large body habitus.
Thermal analysis of microwave power GaAs device chips has been presented that features analytical simplicity yet gives quantitative evaluation of thermal reduction effects of two kinds of chip ...peripheral structures, via-holes and bumps. To calculate T/sub max/ (maximum temperature) and R/sub th/ (thermal resistance), the Laplace equation has been solved for a basic chip model under boundary conditions appropriate to peripheral structures. The chip model consisted of three layers features having heat sources at interface of layer 2 and 3. An approximate method for the analysis of field effect transistor (FET) unit with bumps has been newly proposed. A good agreement has been found between the calculated and measured R/sub th/ and its reduction effect, verifying the usefulness of the present analysis in the thermal design of device chips.
Drosophila genetic studies suggest that in the Wingless (Wg) signaling pathway, the segment polarity gene products, Dishevelled (Dsh), Zeste-white 3 (ZW-3), and Armadillo (Arm), work sequentially; wg ...and dsh negatively regulate zw-3, which in turn down-regulates arm. To biochemically analyze interactions between the Wg pathway and Drosophila E-cadherin (DE-cadherin) which bind to Arm, we overexpressed Dsh, ZW-3, and Arm, in the Drosophila wing disc cell line, clone 8, which responds to Wg signal. Dsh overexpression led to accumulation of Arm primarily in the cytosol and elevation of DE-cadherin at cell junctions. Overexpression of wild-type and dominant-negative forms of ZW-3 decreased and increased Arm levels, respectively, indicating that modulation in zw-3 activity negatively regulates Arm levels. Overexpression of an Arm mutant with an amino-terminal deletion elevated DE-cadherin levels, suggesting that Dsh-induced DE-cadherin elevation is caused by the Arm accumulation induced by Dsh. Moreover, the Dsh-, dominant-negative ZW-3-, and truncated Arm-induced accumulation of DE-cadherin protein was accompanied by a marked increase in the steady-state levels of DE-cadherin mRNA, suggesting that transcription of DE-cadherin is activated by Wg signaling. In addition, overexpression of DE-cadherin elevated Arm levels by stabilizing Arm at cell-cell junctions.
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