This study was conducted to define the underlying molecular mechanism of tripartite motif (TRIM) 59-induced invasion of ectopic endometrial stromal cells in endometriosis. Primary endometriosis ectopic endometrial stromal cells and normal endometrial cells were isolated and purified. Western blot was used to detect the expression of TRIM59, protein phosphatase Mg2+/Mn2+-dependent 1A (PPM1A), smad2/3, and phosphorylated (p)-smad2/3. Lentiviral vector-mediated TRIM59 interference and overexpression were established. Cell Counting Kit-8 assay was used to detect cell proliferation, and the Transwell migration assay was used to detect cell invasion. Matrix metalloproteinase (MMP-2), MMP9, smad2/3, and p-smad2/3 expressions were also detected using Western blot analysis; degradation of PPM1A was verified to be through ubiquitination. We found that TRIM59 expression levels in the endometriosis group was significantly higher compared with the normal group (P < 0.05), whereas the expression levels of PPM1A in the endometriosis group were significantly lower (P < 0.05). Endometriosis did not alter smad2/3 (P > 0.05) expression. However, after activating smad2/3 by phosphorylation, the expression of p-smad2/3 in the endometriosis group was significantly higher compared with the normal group (P < 0.05). The content of PPM1A in the TRIM59 overexpression group was significantly lower than that in the control group (P < 0.001), whereas the content of PPM1A in the siTRIM59 group was significantly higher than that in the control group (P < 0.001). In addition, there were no significant differences in the mRNA levels of PPM1A among the five groups, indicating that TRIM59 affects the expression of PPM1A at the posttranslational level (P < 0.05). Overexpression of TRIM59 significantly promoted the ubiquitination of PPM1A. We conclude that TRIM59 inhibits PPM1A through ubiquitination and activates the transforming growth factor-β/Smad pathway to promote the invasion of ectopic endometrial stromal cells in endometriosis.
Keywords: TGF-β/Smad; endometriosis; tripartite motif protein; ubiquitination.