MARC 主機 00000nam  2200301   4500 
001    AAI3390191 
005    20101222085247.5 
008    101222s2009    ||||||||||||||||| ||eng d 
020    9781109582932 
035    (UMI)AAI3390191 
040    UMI|cUMI 
100 1  Overgaard, Christian Edmund 
245 10 Deciliation dramatically alters epithelial function 
300    114 p 
500    Source: Dissertation Abstracts International, Volume: 71-
       02, Section: B, page: 0747 
500    Adviser: Charles Yeaman 
502    Thesis (Ph.D.)--The University of Iowa, 2009 
520    Primary cilia are sensory organelles present on most 
       differentiated cells. Their assembly or function is 
       impaired in several human diseases, including polycystic 
       kidney disease (PKD). However, the mechanism by which 
       ciliary dysfunction contributes to these pathologies is 
       incompletely understood. PKD is characterized by altered 
       trans-epithelial fluid transport, due to the 
       mislocalization of ion pumps and changes in tight 
       junctions. How ciliary dysregulation might lead to such 
       changes in cell polarity and tight-junction function has 
       not been shown. The overall hypothesis of this thesis is 
       that ciliary dysfunction promotes specific changes in 
       epithelial junctions and cell polarity that contribute to 
       PKD. We developed an experimental model in which to test 
       whether ciliary disruption indeed causes changes in cell 
       polarity and tight junctions, and used it in conjunction 
       with well-established methods to chemically induce ciliary
       shedding from cells, and with assays measuring the 
       distribution of surface and secretory proteins in Madin-
       Darby canine kidney (MDCK) cells. This analysis revealed 
       that several proteins, including Na/K-ATPase, were 
       mislocalized following deciliation and that tight 
       junctions became less permeable to paracellular ion flux. 
       We infer that the combined effects of mislocalized ion 
       transporters and increased tight-junction barrier function
       contribute to cyst formation in PKD. The functional 
       specificity of tight junctions is determined by their 
       expression of claudins, a protein family consisting of 24 
       members. Of these, claudin 2 expression has been shown to 
       lead to an increase in junctional leakiness. We found that
       upon deciliation, claudin 2 expression was lost and trans-
       epithelial resistance increased 3-fold. The signaling 
       pathway connecting deciliation to claudin 2 repression 
       required ERK activation; phospho-ERK levels were elevated 
       after exposure to deciliation stimuli, and an inhibitor of
       ERK activation blocked claudin 2 loss. The down-regulation
       of claudin 2 did not involve post-translational regulation,
       because protein half-life was not altered following 
       deciliation. In contrast, the half-life of claudin 2 mRNA 
       was greatly reduced in deciliated cells. Finally, when 
       murine claudin 2 was ectopically expressed in MDCK cells, 
       its expression was also suppressed upon deciliation. 
       Collectively, these results support a model in which 
       deciliation causes an ERK-dependent decrease in claudin 2 
       mRNA stability, and highlight a mechanism whereby ciliary 
       dysregulation might contribute to altered trans-epithelial
       fluid transport associated with PKD 
590    School code: 0096 
650  4 Biology, Cell 
690    0379 
710 2  The University of Iowa.|bAnatomy & Cell Biology 
773 0  |tDissertation Abstracts International|g71-02B 
856 40 |u