TY - JOUR
T1 - The ISG15-specific protease USP18 regulates stability of PTEN
AU - Mustachio, Lisa Maria
AU - Kawakami, Masanori
AU - Lu, Yun
AU - Rodriguez-Canales, Jaime
AU - Mino, Barbara
AU - Behrens, Carmen
AU - Wistuba, Ignacio
AU - Bota-Rabassedas, Neus
AU - Yu, Jun
AU - Jack Lee, J.
AU - Roszik, Jason
AU - Zheng, Lin
AU - Liu, Xi
AU - Freemantle, Sarah J.
AU - Dmitrovsky, Ethan
N1 - Funding Information:
We thank members of the Dmitrovsky laboratory for their helpful consultation. This study was supported by the National Institutes of Health (NIH) and National Cancer Institute (NCI) grants R01-CA087546 (ED) and R01-CA190722 (ED and SJF), a Samuel Waxman Cancer Research Foundation Award (ED), a UT-STARs award (ED), and an American Cancer Society Clinical Research Professorship (ED).
PY - 2017
Y1 - 2017
N2 - The ubiquitin-like modifier interferon-stimulated gene 15 (ISG15) is implicated in both oncogenic and tumor suppressive programs. Yet, few ISGylation substrates are known and functionally validated in cancer biology. We previously found specific oncoproteins were substrates of ISGylation and were stabilized by the ISG15-specific deubiquitinase (DUB) ubiquitin specific peptidase 18 (USP18). Using reverse-phase protein arrays (RPPAs), this study reports that engineered loss of the DUB USP18 destabilized the tumor suppressor protein phosphatase and tensin homologue (PTEN) in both murine and human lung cancer cell lines. In contrast, engineered gain of USP18 expression in these same lung cancer cell lines stabilized PTEN protein. Using the protein synthesis inhibitor cycloheximide (CHX), USP18 knockdown was shown to destabilize PTEN whereas USP18 overexpression stabilized PTEN protein. Interestingly, repression of USP18 decreased cytoplasmic PTEN relative to nuclear PTEN protein levels. We sought to identify mechanisms engaged in this PTEN protein destabilization using immunoprecipitation assays and found ISG15 directly conjugated with PTEN. To confirm translational relevance of this work, USP18 and PTEN immunohistochemical expression were compared in comprehensive lung cancer arrays. There was a significant (P < 0.0001) positive correlation and association between PTEN and USP18 protein expression profiles in human lung cancers. Taken together, this study identified PTEN as a previously unrecognized substrate of the ISGylation post-translational modification pathway. The deconjugase USP18 serves as a novel regulator of PTEN stability. This indicates inhibition of ISGylation is therapeutically relevant in cancers.
AB - The ubiquitin-like modifier interferon-stimulated gene 15 (ISG15) is implicated in both oncogenic and tumor suppressive programs. Yet, few ISGylation substrates are known and functionally validated in cancer biology. We previously found specific oncoproteins were substrates of ISGylation and were stabilized by the ISG15-specific deubiquitinase (DUB) ubiquitin specific peptidase 18 (USP18). Using reverse-phase protein arrays (RPPAs), this study reports that engineered loss of the DUB USP18 destabilized the tumor suppressor protein phosphatase and tensin homologue (PTEN) in both murine and human lung cancer cell lines. In contrast, engineered gain of USP18 expression in these same lung cancer cell lines stabilized PTEN protein. Using the protein synthesis inhibitor cycloheximide (CHX), USP18 knockdown was shown to destabilize PTEN whereas USP18 overexpression stabilized PTEN protein. Interestingly, repression of USP18 decreased cytoplasmic PTEN relative to nuclear PTEN protein levels. We sought to identify mechanisms engaged in this PTEN protein destabilization using immunoprecipitation assays and found ISG15 directly conjugated with PTEN. To confirm translational relevance of this work, USP18 and PTEN immunohistochemical expression were compared in comprehensive lung cancer arrays. There was a significant (P < 0.0001) positive correlation and association between PTEN and USP18 protein expression profiles in human lung cancers. Taken together, this study identified PTEN as a previously unrecognized substrate of the ISGylation post-translational modification pathway. The deconjugase USP18 serves as a novel regulator of PTEN stability. This indicates inhibition of ISGylation is therapeutically relevant in cancers.
KW - And lung cancer
KW - ISG15
KW - PTEN
KW - Protein stability
KW - USP18
UR - http://www.scopus.com/inward/record.url?scp=85009476576&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85009476576&partnerID=8YFLogxK
U2 - 10.18632/oncotarget.13914
DO - 10.18632/oncotarget.13914
M3 - Article
C2 - 27980214
AN - SCOPUS:85009476576
SN - 1949-2553
VL - 8
SP - 3
EP - 14
JO - Oncotarget
JF - Oncotarget
IS - 1
ER -