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Articles by A Yamamoto
Total Records ( 15 ) for A Yamamoto
  A. K Stewart , A Yamamoto , M Nakakuki , T Kondo , S. L Alper and H. Ishiguro

Pancreatic ductal epithelium produces a HCO3-rich fluid. HCO3 transport across ductal apical membranes has been proposed to be mediated by both SLC26-mediated Cl/HCO3 exchange and CFTR-mediated HCO3 conductance, with proportional contributions determined in part by axial changes in gene expression and luminal anion composition. In this study we investigated the characteristics of apical Cl/HCO3 exchange and its functional interaction with Cftr activity in isolated interlobular ducts of guinea pig pancreas. BCECF-loaded epithelial cells of luminally microperfused ducts were alkalinized by acetate prepulse or by luminal Cl removal in the presence of HCO3-CO2. Intracellular pH recovery upon luminal Cl restoration (nominal Cl/HCO3 exchange) in cAMP-stimulated ducts was largely inhibited by luminal dihydro-DIDS (H2DIDS), accelerated by luminal CFTR inhibitor inh-172 (CFTRinh-172), and was insensitive to elevated bath K+ concentration. Luminal introduction of CFTRinh-172 into sealed duct lumens containing BCECF-dextran in HCO3-free, Cl-rich solution enhanced cAMP-stimulated HCO3 secretion, as calculated from changes in luminal pH and volume. Luminal Cl removal produced, after a transient small depolarization, sustained cell hyperpolarization of ~15 mV consistent with electrogenic Cl/HCO3 exchange. The hyperpolarization was inhibited by H2DIDS and potentiated by CFTRinh-172. Interlobular ducts expressed mRNAs encoding CFTR, Slc26a6, and Slc26a3, as detected by RT-PCR. Thus Cl-dependent apical HCO3 secretion in pancreatic duct is mediated predominantly by an Slc26a6-like Cl/HCO3 exchanger and is accelerated by inhibition of CFTR. This study demonstrates functional coupling between Cftr and Slc26a6-like Cl/HCO3 exchange activity in apical membrane of guinea pig pancreatic interlobular duct.

  G. B Kyei , C Dinkins , A. S Davis , E Roberts , S. B Singh , C Dong , L Wu , E Kominami , T Ueno , A Yamamoto , M Federico , A Panganiban , I Vergne and V. Deretic

Autophagy is a cytoplasmic degradative pathway that can participate in biosynthetic processes, as in the yeast Cvt pathway, but is more commonly known for its functions in removing damaged or surplus organelles and macromolecular complexes. Here, we find that autophagy intersects with human immunodeficiency virus (HIV) biogenesis, mirroring the above dichotomy. Early, nondegradative stages of autophagy promoted HIV yields. HIV Gag-derived proteins colocalized and interacted with the autophagy factor LC3, and autophagy promoted productive Gag processing. Nevertheless, when autophagy progressed through maturation stages, HIV was degraded. This, however, does not occur, as the HIV protein Nef acts as an antiautophagic maturation factor through interactions with the autophagy regulatory factor Beclin 1, thus protecting HIV from degradation. The dual interaction of HIV with the autophagy pathway enhances viral yields by using the early stages while inhibiting the late stages of autophagy. The role of Nef in the latter process enhances yields of infectious HIV and may be of significance for progression to clinical AIDS.

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