| First Author | Tiwari A | Year | 2019 |
| Journal | Invest Ophthalmol Vis Sci | Volume | 60 |
| Issue | 2 | Pages | 731-740 |
| PubMed ID | 30786277 | Mgi Jnum | J:271683 |
| Mgi Id | MGI:6280602 | Doi | 10.1167/iovs.18-26423 |
| Citation | Tiwari A, et al. (2019) KLF4 Regulates Corneal Epithelial Cell Cycle Progression by Suppressing Canonical TGF-beta Signaling and Upregulating CDK Inhibitors P16 and P27. Invest Ophthalmol Vis Sci 60(2):731-740 |
| abstractText | Purpose: Kruppel-like factor 4 (KLF4) promotes corneal epithelial (CE) cell fate while suppressing mesenchymal properties. TGF-beta plays a crucial role in cell differentiation and development, and if dysregulated, it induces epithelial-mesenchymal transition (EMT). As KLF4 and TGF-beta regulate each other in a context-dependent manner, we evaluated the role of the crosstalk between KLF4 and TGF-beta-signaling in CE homeostasis. Methods: We used spatiotemporally regulated ablation of Klf4 within the adult mouse CE in ternary transgenic Klf4Delta/DeltaCE (Klf4LoxP/LoxP/ Krt12rtTA/rtTA/ Tet-O-Cre) mice and short hairpin RNA (shRNA)-mediated knockdown or lentiviral vector-mediated overexpression of KLF4 in human corneal limbal epithelial (HCLE) cells to evaluate the crosstalk between KLF4 and TGF-beta-signaling components. Expression of TGF-beta signaling components and cyclin-dependent kinase (CDK) inhibitors was quantified by quantitative PCR, immunoblots, and/or immunofluorescent staining. Results: CE-specific ablation of Klf4 resulted in (1) upregulation of TGF-beta1, -beta2, -betaR1, and -betaR2; (2) downregulation of inhibitory Smad7; (3) hyperphosphorylation of Smad2/3; (4) elevated nuclear localization of phospho-Smad2/3 and Smad4; and (5) downregulation of CDK inhibitors p16 and p27. Consistently, shRNA-mediated knockdown of KLF4 in HCLE cells resulted in upregulation of TGF-beta1 and -beta2, hyperphosphorylation and nuclear localization of SMAD2/3, downregulation of SMAD7, and elevated SMAD4 nuclear localization. Furthermore, overexpression of KLF4 in HCLE cells resulted in downregulation of TGF-beta1, -betaR1, and -betaR2 and upregulation of SMAD7, p16, and p27. Conclusions: Collectively, these results demonstrate that KLF4 regulates CE cell cycle progression by suppressing canonical TGF-beta signaling and overcomes the undesirable concomitant decrease in TGF-beta-dependent CDK inhibitors p16 and p27 expression by directly upregulating them. |
