Japanese Journal of Veterinary Research;Volume 58, Number 2

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The forced aggresome formation of a bovine anion exchanger 1 (AE1) mutant through association with ΔF508-cystic fibrosis transmembrane conductance regulator upon proteasome inhibition in HEK293 cells

Adachi, Hirokazu;Kurooka, Takao;Otsu, Wataru;Inaba, Mutsumi

Permalink : http://hdl.handle.net/2115/43312
KEYWORDS : AE1;aggresome;CFTR;ER;proteasomal;ERAD

Abstract

The endoplasmic reticulum (ER)-associated degradation of various polytopic proteins, involving the most common mutant of cystic fibrosis transmembrane-conductance regulator (CFTR), ΔF508-CFTR, involves retrotranslocation of the polypeptide into the cytosol, leading to aggresome formation when the proteasome activity is attenuated. By contrast, an R664X nonsense mutant of the bovine anion exchanger 1 (AE1) is retained in the ER and does not form aggresomes upon proteasome inhibition in transfected HEK293 cells. Here, we report that R664X AE1 formed a large cytoplasmic aggregate when cells co-transfected with enhanced green fluorescence protein (EGFP)-ΔF508-CFTR were exposed to the proteasome inhibitor lactacystin. R664X AE1 and EGFP-ΔF508-CFTR showed co-localization in the aggregates and signals of which coincided with γ-tubulin and were caged by vimentin at the pericentriolar locus, demonstrating aggresome formation. On the other hand, EGFP-AnkN90, consisting of the N-terminal AE1 binding domain of ankyrin, a ytoplasmic protein, also exhibited co-localization with R664X AE1, but was found throughout the ER. Moreover, R664X-mutant protein was specifically immunoprecipitated with EGFP-ΔF508-CFTR from the cells co-expressing these proteins. These findings indicate that R664X AE1 is forcibly extracted from the ER to reside in aggresomes through association with ΔF508-CFTR.

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