Dephosphorylation of the transcriptional cofactor NACA by the PP1A phosphatase enhances cJUN transcriptional activity and osteoblast differentiation
| Autor: | René St-Arnaud, William N. Addison, Martin Pellicelli |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
Transcription Genetic Proto-Oncogene Proteins c-jun Protein subunit Phosphatase Active Transport Cell Nucleus Response Elements Proto-Oncogene Mas Biochemistry Dephosphorylation Mice 03 medical and health sciences Protein Phosphatase 1 Animals Humans Gene Regulation Phosphorylation Molecular Biology Transcription factor Cell Nucleus Osteoblasts 030102 biochemistry & molecular biology Kinase Chemistry Nuclear Proteins Cell Differentiation Protein phosphatase 1 Cell Biology Cell biology HEK293 Cells 030104 developmental biology Matrix Metalloproteinase 9 NACA Molecular Chaperones Transcription Factors |
| Zdroj: | J Biol Chem |
| ISSN: | 0021-9258 |
| Popis: | The transcriptional cofactor nascent polypeptide-associated complex and co-regulator α (NACA) regulates osteoblast maturation and activity. NACA functions, at least in part, by binding to Jun proto-oncogene, AP-1 transcription factor subunit (cJUN) and potentiating the transactivation of AP-1 targets such as osteocalcin (Bglap) and matrix metallopeptidase 9 (Mmp9). NACA activity is modulated by phosphorylation carried out by several kinases, but a phosphatase regulating NACA's activity remains to be identified. Here, we used affinity purification with MS in HEK293T cells to isolate NACA complexes and identified protein phosphatase 1 catalytic subunit α (PP1A) as a NACA-associated Ser/Thr phosphatase. NACA interacted with multiple components of the PP1A holoenzyme complex: the PPP1CA catalytic subunit and the regulatory subunits PPP1R9B, PPP1R12A and PPP1R18. MS analysis revealed that NACA co-expression with PPP1CA causes dephosphorylation of NACA at Thr-89, Ser-151, and Thr-174. NACA Ser/Thr-to-alanine variants displayed increased nuclear localization, and NACA dephosphorylation was associated with specific recruitment of novel NACA interactants, such as basic transcription factor 3 (BTF3) and its homolog BTF3L4. NACA and PP1A cooperatively potentiated cJUN transcriptional activity of the AP-1–responsive MMP9-luciferase reporter, which was abolished when Thr-89, Ser-151, or Thr-174 were substituted with phosphomimetic aspartate residues. We confirmed the NACA–PP1A interaction in MC3T3-E1 osteoblastic cells and observed that NACA phosphorylation status at PP1A-sensitive sites is important for the regulation of AP-1 pathway genes and for osteogenic differentiation and matrix mineralization. These results suggest that PP1A dephosphorylates NACA at specific residues, impacting cJUN transcriptional activity and osteoblast differentiation and function. |
| Databáze: | OpenAIRE |
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