Document Detail


Functional characterization of a human aquaporin 0 mutation that leads to a congenital dominant lens cataract.
MedLine Citation:
PMID:  18501347     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The aquaporin (AQP) transmembrane proteins facilitate the movement of water across the plasma membrane. In the lens, AQP0 is expressed in fiber cells and AQP1 in the epithelium. Recently, two individuals were identified with congenital polymorphic autosomal dominant cataract, due to a single nucleotide base deletion mutation in the lens AQP0. The deletion modified the reading frame resulting in the addition of a premature stop codon. In the present study, we examined the water permeability properties, trafficking and dominant negative effects as well as cytotoxicity due to the mutant AQP0 (Delta213-AQP0) protein. The membrane water permeability (P(w)) of Delta213-AQP0 expressing oocytes (14+/-1 microm/s) was significantly lower than those expressing WT-AQP0 (25+/-3 microm/s). P(w) of water injected control oocytes was 13+/-2 microm/s. Co-expression of WT-AQP0 with Delta213-AQP0 significantly lowered the P(w) (18+/-3 microm/s) compared to WT-AQP0. With or without the EGFP tag, WT-AQP0 protein localized in the plasma membranes of oocytes and cultured cells whereas Delta213-AQP0 was retained in the ER. Forster Resonance Energy Transfer (FRET) showed that WT-AQP0 partly localized with the co-expressed Delta213-AQP0. Co-localization studies suggest that the mutant AQP0 gained its dominant function by trapping the WT-AQP0 in the ER through hetero-oligomerization. Incubating the cells with chemical chaperones, namely, TMAO and DMSO, did not correct the folding/trafficking defects. Cell death in the Delta213-AQP0 expressing cells was due to necrosis caused by the accumulation of Delta213-AQP0 protein in the ER in cytotoxic proportions. The data show that replacement of the distal end of the 6th TM domain and the C-terminal domain of AQP0 due to the deletion mutation resulted in the impairment of cell membrane P(w), localization of the mutant protein in the ER without trafficking to the plasma membrane, and cytotoxicity due to the accumulation of the mutant protein. Cataracts in patients with this mutation might have resulted from the above mentioned consequences.
Authors:
K Varadaraj; S S Kumari; R Patil; M B Wax; R T Mathias
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2008-04-10
Journal Detail:
Title:  Experimental eye research     Volume:  87     ISSN:  0014-4835     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-07-08     Completed Date:  2008-12-04     Revised Date:  2014-09-15    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  9-21     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Aquaporin 1 / genetics
Aquaporins / genetics*
Cataract / congenital,  genetics*
Cell Membrane Permeability
Eye Proteins / genetics*
Humans
Lens, Crystalline / metabolism*
Models, Biological
Mutation
Oocytes / metabolism*
Xenopus laevis
Grant Support
ID/Acronym/Agency:
EY 06391/EY/NEI NIH HHS; R01 EY006391/EY/NEI NIH HHS; R01 EY006391-23/EY/NEI NIH HHS
Chemical
Reg. No./Substance:
0/Aquaporins; 0/Eye Proteins; 0/aquaporin 0; 146410-94-8/Aquaporin 1
Comments/Corrections

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