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A PP2A active site mutant impedes growth and causes misregulation of native catalytic subunit expression
Author(s) -
Lizotte Donna L.,
Blakeslee Joshua J.,
Siryaporn Albert,
Heath Jeffrey T.,
DeLong Alison
Publication year - 2007
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.21514
Subject(s) - protein phosphatase 2 , protein subunit , mutant , biology , gamma aminobutyric acid receptor subunit alpha 1 , microbiology and biotechnology , specificity factor , complementation , wild type , biochemistry , g alpha subunit , gene expression , gene , promoter
Activity of protein phosphatase 2A (PP2A) is tightly regulated and performs a diverse repertoire of cellular functions. Previously we isolated a dominant‐negative active site mutant of the PP2A catalytic (C) subunit using a yeast complementation assay. We have established stable fibroblastic cell lines expressing epitope‐tagged versions of the wild‐type and H118N mutant C subunits and have used these cells to investigate mechanisms that regulate PP2A activity. Cells expressing the mutant C subunit exhibit a decreased growth rate and a prolonged G1 cell cycle phase. The mutant protein is enzymatically inactive, but extracts made from cells expressing the H118N C subunit show normal levels of total PP2A activity in vitro. The H118N mutant shows reduced binding to the regulatory A subunit, but binds normally to the α4 protein, a non‐canonical regulator of PP2A. Expression of the H118N mutant interferes with the normal control of C subunit abundance, causing accumulation of the endogenous wild‐type protein as well as the mutant transgene product. Our results indicate that the H118N mutant isoform retards C subunit turnover and suggest that PP2A C subunit turnover may be important for normal cell cycle progression. J. Cell. Biochem. 103: 1309–1325, 2008. © 2007 Wiley‐Liss, Inc.