Xie Zhang1, Bowei Yin1, Fangfang Zhu1, Guochang Huang1, Hong Li1. 1. 1 Department of Gastroenterology, Ningbo Medical Center, LiHuiLi Hospital, Ningbo 315040, Zhejiang, China ; 2 School of Medicine, Ningbo University, Ningbo 315211, Zhejiang, China ; 3 Ningbo Medical Center, 4 Minimally Invasive Abdominal Surgery, Ningbo Medical Center, LiHuiLi Hospital, Ningbo 315040, Zhejiang Province, China.
Abstract
BACKGROUND: To identify PTEN isoform and explore its potential role in tumor suppression. METHODS: Western blotting, over-expression, shRNA mediated knocking-down, and bioinformatic analysis were used to identify PTEN isoform and test its effect on PI3K-Akt signaling pathway. Cell proliferation, apoptosis, and migration assays were used to test PTEN isoform's biological activities. RESULTS: The PTEN isoform is about 15 kDa bigger than PTEN and its expression is dependent on PTEN status. Immunoprecipitation for PTEN isoform followed by screening with antibodies against ISG15, SUMO1/2/3, Ubiquitin, and Nedd8 showed the identified PTEN isoform is not a general proteinaceous post-translational modification. In addition, overexpression of PTEN cDNA in cells did not generate PTEN isoform whereas knocking-down of PTEN reduced the protein levels of both PTEN and PTEN isoform in a proportional manner. Analysis of PTEN DNA sequence disclosed an alternative translational starting code (CTG) upstream of canonical PTEN coding sequence. Expression of cloned PTEN isoform generated a protein with a size about 15 kDa bigger than PTEN and suppressed PI3K-Akt signaling pathway in cells. Overexpression of PTEN isoform also led to decrease in cell growth and enhanced serum starvation-and UV irradiation-induced apoptosis through activation of Caspase 3. Finally, expression of PTEN isoform inhibited cell migration in scratch assay. CONCLUSIONS: PTEN isoform has PTEN-like activity and might be a new tumor suppressor.
BACKGROUND: To identify PTEN isoform and explore its potential role in tumor suppression. METHODS: Western blotting, over-expression, shRNA mediated knocking-down, and bioinformatic analysis were used to identify PTEN isoform and test its effect on PI3K-Akt signaling pathway. Cell proliferation, apoptosis, and migration assays were used to test PTEN isoform's biological activities. RESULTS: The PTEN isoform is about 15 kDa bigger than PTEN and its expression is dependent on PTEN status. Immunoprecipitation for PTEN isoform followed by screening with antibodies against ISG15, SUMO1/2/3, Ubiquitin, and Nedd8 showed the identified PTEN isoform is not a general proteinaceous post-translational modification. In addition, overexpression of PTEN cDNA in cells did not generate PTEN isoform whereas knocking-down of PTEN reduced the protein levels of both PTEN and PTEN isoform in a proportional manner. Analysis of PTEN DNA sequence disclosed an alternative translational starting code (CTG) upstream of canonical PTEN coding sequence. Expression of cloned PTEN isoform generated a protein with a size about 15 kDa bigger than PTEN and suppressed PI3K-Akt signaling pathway in cells. Overexpression of PTEN isoform also led to decrease in cell growth and enhanced serum starvation-and UV irradiation-induced apoptosis through activation of Caspase 3. Finally, expression of PTEN isoform inhibited cell migration in scratch assay. CONCLUSIONS:PTEN isoform has PTEN-like activity and might be a new tumor suppressor.
Authors: H Sun; R Lesche; D M Li; J Liliental; H Zhang; J Gao; N Gavrilova; B Mueller; X Liu; H Wu Journal: Proc Natl Acad Sci U S A Date: 1999-05-25 Impact factor: 11.205
Authors: D H Teng; R Hu; H Lin; T Davis; D Iliev; C Frye; B Swedlund; K L Hansen; V L Vinson; K L Gumpper; L Ellis; A El-Naggar; M Frazier; S Jasser; L A Langford; J Lee; G B Mills; M A Pershouse; R E Pollack; C Tornos; P Troncoso; W K Yung; G Fujii; A Berson; P A Steck Journal: Cancer Res Date: 1997-12-01 Impact factor: 12.701