Opening the conformation is a master switch for the dual localization and phosphatase activity of PTEN

Abstract

Tumor suppressor PTEN mainly functions at two subcellular locations, the plasma membrane and the nucleus. At the plasma membrane, PTEN dephosphorylates the tumorigenic second messenger PIP3, which drives cell proliferation and migration. In the nucleus, PTEN controls DNA repair and genome stability independently of PIP3. Whereas the concept that a conformational change regulates protein function through post-translational modifications has been well established in biology, it is unknown whether a conformational change simultaneously controls dual subcellular localizations of proteins. Here, we discovered that opening the conformation of PTEN is the crucial upstream event that determines its key dual localizations of this crucial tumor suppressor. We identify a critical conformational switch that regulates PTEN’s localization. Most PTEN molecules are held in the cytosol in a closed conformation by intramolecular interactions between the C-terminal tail and core region. Dephosphorylation of the tail opens the conformation and exposes the membrane-binding regulatory interface in the core region, recruiting PTEN to the membrane. Moreover, a lysine at residue 13 is also exposed and when ubiquitinated, transports PTEN to the nucleus. Thus, opening the conformation of PTEN is a key mechanism that enhances its dual localization and enzymatic activity, providing a potential therapeutic strategy in cancer treatments.

Characterization of PTEN mutations in brain cancer reveals that pten mono-ubiquitination promotes protein stability and nuclear localization

“…PTEN was analyzed using SDS-PAGE followed by immunoblotting with anti-PTEN antibodies. Consistent with the open conformation of PTEN A4 6, 34 , we found greater susceptibility of PTEN A4 -GFP than of PTEN WT -GFP to trypsin digestion (Figs. 7A and B).…”

“…2D and E and S1A). We found that PTEN delEx3 , PTEN L320S , and PTEN T277A had significantly shorter half-lives than PTEN WT or PTEN A4 , which carries alanine substitutions at S380, T382, T383 and S385 that block phosphorylation of C-terminal tail 34, 49 , (Figs. 2D and E).…”

“…We immunopurified GFP fused to PTEN L320S and PTEN T277A , wild-type PTEN (PTEN WT ), a catalytically inactive PTEN C124S , and PTEN with a deletion of exon 3 (PTEN delEx3 ) from HEK293T cells. Equal amounts of immunopurified proteins were used to measure their lipid phosphatase activity against a PIP3 substrate in vitro 34, 49 . While PTEN C124S -GFP and PTEN delEx3 -GFP showed significantly suppressed lipid phosphatase activities, PTEN L320S -GFP and PTEN T277A -GFP showed activities indistinguishable from PTEN WT -GFP (Fig.…”

“…We introduced K13R, which has been shown to block ubiquitination at K13, a cause of proteasomal degradation, and C124S, a mutation that stabilizes PTEN presumably through inhibiting its enzymatic activity 31, 32, 34 . We found that neither of these two mutations rescued the stability of PTEN K13R,L320S -GFP or PTEN C124S,L320S -GFP (Figs.…”

“…The majority of PTEN is located in the cytosol, and only a fraction is recruited to the plasma membrane to precisely control PIP3 levels in a highly regulated manner. We have previously shown that this recruitment process is mediated by the membrane-binding regulatory interface and is regulated by phosphorylation of PTEN 31–34 . The membrane-binding regulatory interface consists of three regions of PTEN and is located on the protein’s surface.…”