Notch and TGF-β pathways cooperatively regulate receptor protein tyrosine phosphatase-κ (PTPRK) gene expression in...

Area of Science:

• Cell Biology
• Molecular Biology
• Dermatology

Background:

• Receptor protein tyrosine phosphatase-κ (PTPRK) dephosphorylates and limits epidermal growth factor receptor (EGFR) function.
• PTPRK expression is modulated by TGF-β/Smad3 signaling and cell-cell contact.
• The Notch pathway is crucial for keratinocyte growth and differentiation and responds to cell-cell contact.

Purpose of the Study:

• To investigate the interplay between Notch and TGF-β signaling pathways in regulating PTPRK expression in human keratinocytes.
• To determine how Notch and TGF-β signaling pathways cooperate to control PTPRK induction.
• To elucidate the combined effect of Notch and TGF-β on PTPRK expression and subsequent EGFR phosphorylation.

Main Methods:

• Utilized γ-secretase inhibitors to suppress Notch signaling.
• Employing knockdown of Notch1.
• Administered soluble Jagged-1 peptide (Jag1) to activate Notch signaling.
• Used TGF-β1 and SB431542 (a TGF-β receptor inhibitor).
• Assessed PTPRK gene expression and EGFR tyrosine phosphorylation.

Main Results:

• Notch signaling suppression reduced cell contact-induced PTPRK expression.
• Jag1 peptide induced PTPRK in sparse keratinocytes.
• TGF-β1 and SB431542 inhibited contact-induced PTPRK expression.
• Notch inhibition significantly reduced TGF-β-induced PTPRK expression.
• Combined Jag1 and TGF-β treatment resulted in higher PTPRK expression and lower EGFR phosphorylation than individual treatments.

Conclusions:

• Notch and TGF-β pathways function synergistically to induce PTPRK expression in human keratinocytes.
• Coordinated Notch and TGF-β signaling leads to increased PTPRK, which suppresses EGFR activation.
• This interplay is critical for regulating keratinocyte function and EGFR signaling homeostasis.