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Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment
07:55

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

Published on: September 25, 2017

A mitochondrial kinase complex is essential to mediate an ERK1/2-dependent phosphorylation of a key regulatory

Cecilia Poderoso1, Daniela P Converso, Paula Maloberti

  • 1Instituto de Investigaciones Moleculares de Enfermedades Hormonales, Neurodegenerativas y Oncológicas (IIMHNO), Department of Human Biochemistry, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina.

Plos One
|January 17, 2008
PubMed

Insights

Mitochondrial ERK1/2 activation is essential for hormone-stimulated steroid synthesis, phosphorylating the steroidogenic acute regulatory (StAR) protein to regulate cholesterol transport. This uncovers a novel role for MAPKs in mitochondrial steroidogenesis.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Endocrinology

Background:

  • Extracellular signal-regulated kinases (ERK1/2) are implicated in hormone-stimulated steroid synthesis, but their precise roles and mechanisms are unclear.
  • Both ERK1/2 activation and steroidogenesis can be regulated by cAMP/cAMP-dependent protein kinase (PKA) and epidermal growth factor (EGF) through distinct pathways.
  • cAMP-induced ERK1/2 activation maximizes steroidogenic rates, unlike EGF-induced activation.

Purpose of the Study:

  • To elucidate the specific roles and mechanisms of ERK1/2 activation in PKA-mediated steroidogenesis.
  • To investigate the localization and regulation of ERK1/2 and its interaction with steroidogenic acute regulatory (StAR) protein.
  • To identify StAR as a direct substrate of ERK1/2 and its functional significance in steroid biosynthesis.

Main Methods:

  • Western blot analysis and confocal microscopy to assess ERK1/2 phosphorylation and localization.
  • Ex vivo experiments to study mitochondrial steroidogenesis and protein interactions.
  • Site-directed mutagenesis (StAR S232A) and transient transfection assays to evaluate StAR phosphorylation and progesterone production.

Main Results:

  • Temporal mitochondrial ERK1/2 activation is obligatory for PKA-mediated steroidogenesis in MA-10 cells.
  • PKA phosphorylates mitochondrial MEK1/2, favoring mitochondrial ERK1/2 activation, while EGF primarily activates cytosolic MEK and nuclear ERK1/2.
  • Mitochondrial StAR interacts with active ERK1/2 and PKA, leading to StAR phosphorylation at Ser(232) in a cholesterol-dependent manner.
  • Mutagenesis of StAR Ser(232) to Alanine (StAR S232A) inhibited ERK1/2 phosphorylation and significantly reduced progesterone production.

Conclusions:

  • Steroidogenic acute regulatory (StAR) protein is a novel substrate of ERK1/2.
  • Mitochondrial ERK1/2 is a key component of a multimeric protein kinase complex regulating cholesterol transport and steroidogenesis.
  • These findings highlight the critical role of MAPKs in mitochondrial function and steroid biosynthesis.

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