Requirement of phosphatase of regenerating liver-3 for the nucleolar localization of nucleolin during the progression of colorectal carcinoma.
Phosphatase of regenerating liver-3 (PRL-3) is a protein tyrosine phosphatase (PTP) that is frequently overexpressed in liver metastases of colorectal carcinomas (CRCs). The PTP activity of the PRL-3 protein is indispensable for the promotion of distant metastasis of CRC; however, little is known about the effect of PRL-3 on cell growth. In this study, we investigated a novel protein that can connect to PRL-3 to modulate the proliferation of CRC cells. In CRC-derived SW480 cells, transduction of ectopic wild-type PRL-3, but not the C104S catalytic "dead" mutant, up-regulated cell proliferation and increased the population of cells at the S and G(2) /M phases. Also, inhibition of PTP activity of the PRL-3 protein by treatment with the PRL-3 inhibitor suppressed cell proliferation in a dose-dependent manner as well as PRL-3 knockdown by RNA interference. Using a comparative study of monodimensional gel electrophoresis of immunoprecipitates from PRL-3-transfected SW480 cells and subsequent mass spectrometry analysis, nucleolar-specific protein nucleolin (NCL) was identified as a novel PRL-3-binding protein. We confirmed physiological interaction between PRL-3 and NCL, and found that PRL-3 phosphatase activity was associated with the suppression of the phospho-NCL levels and nucleolar assembly of NCL protein. In CRC cases, nucleolar NCL expression was correlated not only with higher levels of PRL-3 expression but also with frequent incidence of lymph node metastasis and a higher clinicopathologic stage. These findings suggest that NCL is involved in PRL-3-mediated cancer progression/metastasis signaling, which plays an important role in the acceleration of CRC growth.
Semba
Shuho
S
Division of Pathology, Department of Pathology, Kobe University Graduate School of Medicine, Kobe, Japan. semba@med.kobe-u.ac.jp
Mizuuchi
Eri
E
Yokozaki
Hiroshi
H
D000328:Adult; D000368:Aged; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000737:chemistry*; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000502:physiology*; D010750:Phosphoproteins / Q000032:analysis*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000032:analysis*; D000097796:Nucleolin
D009363:Neoplasm Proteins; D010750:Phosphoproteins; D017027:Protein Tyrosine Phosphatases; D016601:RNA-Binding Proteins; D000097796:Nucleolin; C484730:PTP4A3 protein, human