Depletion of nucleophosmin via transglutaminase 2 cross-linking increases drug resistance in cancer cells.
It has been suggested that nucleophosmin has an anti-apoptotic function via Bax binding. We found that nucleophosmin is a substrate of transglutaminase 2 (TGase 2) in cancer cells. Increased expression of TGase 2 expression is highly associated with drug resistance, and polymerization of nucleophosmin by TGase 2 also can be correlated with the drug resistance of cancer cells. In the present study, an accumulation of nucleophosmin in cytosol was detected when doxorubicin was treated to cancer cells, and it was found, moreover, that an increase of cytosolic nucleophosmin can result in drug-induced apoptosis. Nucleophosmin was polymerized by TGase 2, and the polymerization was inhibited with the TGase 2 inhibitor, cystamine, in vitro. The nucleophosmin level in the cytosolic cell fraction was reduced when TGase 2 was expressed, and the reduced nucleophosmin level was rescued by cystamine treatment. Moreover, nucleophosmin cross-linked by TGase 2 was eradicated in MCF7 cells via the ubiquitin-proteasomal pathway. In parallel with this nucleophosmin-level restoration, the pro-apoptotic Bax protein level was increased. Therefore, depletion of cytosolic nucleophosmin by TGase 2 can decrease Bax protein stability and lead to anti-apoptosis. Drug-resistant cancer cells became sensitive to doxorubicin treatment when nucleophosmin was expressed in cytosol. Taking these results together, it can be concluded that TGase 2 inhibits accumulation of cytosolic nucleophosmin through polymerization, which results in drug resistance in cancer cells.
Park
Kang-Seo
KS
Molecular Oncology Branch, Division of Basic and Applied Sciences, Research Institute, National Cancer Center, Gyeonggi 411-769, Republic of Korea.
Han
Byeong-Gu
BG
Lee
Kyoung Hwa
KH
Kim
Dae-Seok
DS
Kim
Jung-Mo
JM
Jeon
Hyesung
H
Kim
Hyoun Sook
HS
Suh
Se Won
SW
Lee
Eunjoo H
EH
Kim
Soo-Youl
SY
Lee
Byung Il
BI
D001704:Biopolymers; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D019008:Drug Resistance, Neoplasm; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D046529:Microscopy, Electron, Transmission; D009687:Nuclear Proteins / Q000378:metabolism* / Q000648:ultrastructure; D000090243:Nucleophosmin; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry; D011503:Transglutaminases / Q000378:metabolism*
D001704:Biopolymers; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins