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cAMP/Protein Kinase A Signaling Inhibits Dlx5 Expression via Activation of CREB and Subsequent C/EBPβ Induction in

Hye-Lim Lee1,2, Abdul S Qadir3,4, Hyun-Jung Park5

  • 1Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826, Korea. hyelim.lee.lhl@gmail.com.

International Journal of Molecular Sciences
|October 17, 2018
PubMed

Insights

Stimulating adipogenesis with IBMX reduces Distal-less homeobox 5 (Dlx5) expression. This occurs via cAMP/PKA/CREB signaling, leading to C/EBPβ binding the Dlx5 promoter and suppressing transcription.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Distal-less homeobox 5 (Dlx5) is a known negative regulator of adipogenesis.
  • The precise mechanisms by which adipogenic stimuli downregulate Dlx5 remain unclear.
  • Understanding these mechanisms is crucial for controlling fat cell differentiation.

Purpose of the Study:

  • To investigate the role of cAMP/PKA signaling in the downregulation of Dlx5 during adipogenesis.
  • To identify the key transcription factors and regulatory elements involved in Dlx5 suppression.
  • To elucidate the molecular pathway linking adipogenic stimuli to Dlx5 transcriptional repression.

Main Methods:

  • 3T3-L1 preadipocytes were treated with cAMP-inducing agents (IBMX, forskolin, 8-CPT-cAMP).
  • Dlx5 mRNA and protein levels were assessed.
  • Forced expression and knockdown (siRNA) of CREB and C/EBPβ were performed.
  • Luciferase reporter assays and chromatin immunoprecipitation (ChIP) were utilized to analyze promoter activity and transcription factor binding.

Main Results:

  • cAMP/PKA signaling significantly downregulated Dlx5 mRNA and protein.
  • CREB acts upstream of C/EBPβ in this pathway.
  • C/EBPβ knockdown rescued Dlx5 expression in IBMX-treated cells.
  • A specific Dlx5 promoter region (-774 to -95 bp) containing a C/EBPβ binding site (site-1) was essential for transcriptional suppression.
  • ChIP confirmed C/EBPβ binding to site-1 on the Dlx5 promoter.

Conclusions:

  • IBMX-induced adipogenesis involves activation of the cAMP/PKA/CREB signaling pathway.
  • This pathway leads to the upregulation of C/EBPβ.
  • C/EBPβ directly binds to the Dlx5 promoter at site-1, suppressing Dlx5 transcription and contributing to adipogenesis.
Keywords:
C/EBPβCREBDlx5IBMXadipocyte

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