ABSTRACT
WW domain-containing oxidoreductase (WWOX), a putative tumour suppressor, is suggested to be involved in the hyperphosphorylation of Alzheimer's Tau. Tau is a microtubule-associated protein that has an important role in microtubule assembly and stability. Glycogen synthase kinase 3ß (GSK3ß) has a vital role in Tau hyperphosphorylation at its microtubule-binding domains. Hyperphosphorylated Tau has a low affinity for microtubules, thus disrupting microtubule stability. Bioinformatics analysis indicated that WWOX contains two potential GSK3ß-binding FXXXLI/VXRLE motifs. Immunofluorescence, immunoprecipitation and molecular modelling showed that WWOX interacts physically with GSK3ß. We demonstrated biochemically that WWOX can bind directly to GSK3ß through its short-chain alcohol dehydrogenase/reductase domain. Moreover, the overexpression of WWOX inhibited GSK3ß-stimulated S396 and S404 phosphorylation within the microtubule domains of Tau, indicating that WWOX is involved in regulating GSK3ß activity in cells. WWOX repressed GSK3ß activity, restored the microtubule assembly activity of Tau and promoted neurite outgrowth in SH-SY5Y cells. Conversely, RNAi-mediated knockdown of WWOX in retinoic acid (RA)-differentiated SH-SY5Y cells inhibited neurite outgrowth. These results suggest that WWOX is likely to be involved in regulating GSK3ß activity, reducing the level of phosphorylated Tau, and subsequently promoting neurite outgrowth during neuron differentiation. In summary, our data reveal a novel mechanism by which WWOX promotes neuronal differentiation in response to RA.
Subject(s)
Glycogen Synthase Kinase 3/metabolism , Neurogenesis/drug effects , Neurons/metabolism , Oxidoreductases/metabolism , Tumor Suppressor Proteins/metabolism , Amino Acid Motifs , Amino Acid Sequence , Binding Sites , Cell Line, Tumor , Glycogen Synthase Kinase 3/antagonists & inhibitors , Glycogen Synthase Kinase 3/genetics , Glycogen Synthase Kinase 3 beta , Humans , Microtubules/metabolism , Molecular Dynamics Simulation , Molecular Sequence Data , Neurons/cytology , Oxidoreductases/antagonists & inhibitors , Oxidoreductases/chemistry , Phosphorylation , Protein Binding , Protein Structure, Tertiary , RNA Interference , RNA, Small Interfering/metabolism , Tretinoin/pharmacology , Tumor Suppressor Proteins/antagonists & inhibitors , Tumor Suppressor Proteins/chemistry , WW Domain-Containing Oxidoreductase , tau Proteins/antagonists & inhibitors , tau Proteins/genetics , tau Proteins/metabolismABSTRACT
The appearance of cloudy peritoneal dialysis effluent in combination with the clinical manifestations of peritonitis usually heralds infectious peritonitis and the diagnosis is established with routine cultures. However, patients may present with culture-negative cloudy dialysate effluent and after ruling out atypical infectious etiologies, other intraabdominal causes should be considered in the differential diagnosis. A 57-year-old male with uremia on continuous ambulatory peritoneal dialysis with a pertinent history of restrictive cardiomyopathy and chronic atrial fibrillation suffered from abdominal pain and persistent culture-negative cloudy peritoneal dialysate. Clinical improvement was limited after empiric antibiotic treatment and all bacteriologic workups were negative. Isolated spleen infarction, a rare cause of culture-negative peritonitis, was disclosed by abdominal computed tomography. Spleen infarction is still an unrecognized cause of culture-negative peritonitis and is frequently overlooked. A high degree of suspicion is needed in CAPD patients with thromboembolism risk who present with unexplained persistent abdominal pain and cloudy PD effluent.
