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CaMKIV-Mediated Phosphorylation Inactivates Freud-1/CC2D1A Repression for Calcium-Dependent 5-HT1A Receptor Gene

Kimberly Galaraga1, Anastasia Rogaeva1, Nathan Biniam1

  • 1Ottawa Hospital Research Institute (Neuroscience), Ottawa Brain and Mind Research Institute, 451 Smyth Road, Ottawa, ON K1H-8M5, Canada.

International Journal of Molecular Sciences
|June 19, 2024
PubMed

Insights

Calcium calmodulin-dependent protein kinase (CaMK) phosphorylation inhibits the Freud-1 gene, increasing serotonin-1A receptor expression. This mechanism regulates cognitive development and antidepressant response.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Genetics

Background:

  • Calcium calmodulin-dependent protein kinase (CaMK) regulates calcium-induced neural gene activation.
  • Freud-1 (CC2D1A) is a gene that represses serotonin-1A (5-HT1A) and dopamine-D2 receptor genes, and its dysregulation is linked to mental illnesses.
  • Altered expression of Freud-1-regulated genes is implicated in major depression and schizophrenia.

Purpose of the Study:

  • To investigate the hypothesis that CaMK inhibits Freud-1 activity through phosphorylation.
  • To elucidate the specific CaMK isoforms and phosphorylation sites involved in Freud-1 regulation.
  • To understand the impact of CaMK-mediated Freud-1 inhibition on target gene expression and its implications for neurological function.

Main Methods:

  • Purified Freud-1 protein was incubated with CaMKIIα and CaMKIV to assess phosphorylation.
  • Site-directed mutagenesis was used to create Freud-1 mutants (Ser644Ala, Thr780Ala).
  • Experiments were conducted in human SK-N-SH neuroblastoma and HEK-293 cells to study phosphorylation, DNA binding, and repressor activity.

Main Results:

  • CaMKIIα and CaMKIV increased Freud-1 phosphorylation, particularly at Thr780.
  • CaMK activation reduced Freud-1 binding to the 5-HT1A and dopamine-D2 receptor gene elements.
  • Active CaMKIV, but not CaMKIIα, inhibited Freud-1 repressor activity in cells, with mutants showing resistance.
  • CaMKIV-induced phosphorylation of Freud-1 at Thr780 up-regulates target genes like the 5-HT1A receptor.

Conclusions:

  • CaMKIV-induced phosphorylation at Thr780 is a key mechanism for inhibiting Freud-1 repressor activity.
  • This inhibition leads to the de-repression and up-regulation of target genes, including the 5-HT1A receptor.
  • The CaMKIV-Freud-1 pathway offers a novel mechanism for regulating 5-HT1A receptor expression, impacting cognitive development, behavior, and antidepressant response.
Keywords:
5-HT1A receptorgene repressionmajor depressive disorderphosphorylationraphetranscription factor

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