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Dicer up-regulation by inhibition of specific proteolysis in differentiating monocytic cells

Devaraj Basavarajappa1, Stella Uebbing1,2,3, Marius Kreiss3

  • 1Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden.

Proceedings of the National Academy of Sciences of the United States of America
|March 30, 2020
PubMed

Insights

Dicer proteolysis in monocytic cells is regulated by differentiation. Inhibiting this proteolysis increases full-length Dicer and micro-RNA (miRNA) production, crucial for cellular regulation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Dicer is a key ribonuclease III enzyme essential for micro-RNA (miRNA) biosynthesis.
  • Dicer expression and activity are critical for regulating gene expression via miRNAs.
  • Understanding Dicer regulation in immune cells like monocytes is vital for immune function.

Purpose of the Study:

  • To investigate the regulation of Dicer expression in monocytic cells, focusing on proteolysis.
  • To identify factors and conditions that modulate Dicer levels and activity during monocyte differentiation.
  • To explore the impact of Dicer regulation on miRNA biosynthesis and cellular function.

Main Methods:

  • Western blotting to detect Dicer protein levels and fragments in Mono Mac 6 (MM6) cells and primary monocytes.
  • Mass spectrometry to identify Dicer cleavage sites.
  • Treatment with differentiation agents (TGF-β, 1,25diOHvitD3, M-CSF, GM-CSF), stimuli (zymosan, LPS, PGE2), and protease inhibitors (AEBSF).

Main Results:

  • Full-length Dicer was undetectable in undifferentiated MM6 cells, with only a 50-kDa fragment present.
  • Differentiation stimuli (zymosan, LPS, TGF-β, 1,25diOHvitD3) induced full-length Dicer, alongside 170- and 50-kDa fragments, indicating specific cleavage.
  • Prostaglandin E2 (PGE2) and serine protease inhibitor AEBSF up-regulated full-length Dicer, suggesting inhibition of constitutive Dicer proteolysis.

Conclusions:

  • Monocyte differentiation inhibits constitutive Dicer proteolysis, leading to increased full-length Dicer and subsequent miRNA formation.
  • Dicer regulation via proteolysis is a key mechanism controlling miRNA biosynthesis in monocytic cells.
  • Targeting Dicer proteolysis may offer a novel approach to modulate miRNA production in immune cells.
Keywords:
PGE2macrophagemiRNA

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