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Related Experiment Video

Updated: Mar 9, 2026

Biochemical Reconstitution of Steroid Receptor•Hsp90 Protein Complexes and Reactivation of Ligand Binding
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ACTH Action on StAR Biology.

Barbara J Clark1

  • 1Department of Biochemistry and Molecular Genetics, University of Louisville Louisville, KY, USA.

Frontiers in Neuroscience
|December 22, 2016
PubMed
Summary

The Steroidogenic Acute Regulatory protein (StAR) is crucial for delivering cholesterol to mitochondria, a key step in steroid hormone synthesis. Understanding StAR phosphorylation by protein kinase A (PKA) is vital for elucidating its function in steroidogenesis.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Biochemistry

Background:

  • Adrenocorticotropin hormone (ACTH) stimulates glucocorticoid synthesis via the cAMP-protein kinase A (PKA) pathway.
  • Steroidogenic Acute Regulatory protein (StAR) is essential for cholesterol transport to mitochondria, initiating steroid hormone biosynthesis.
  • The precise mechanism of StAR action in cholesterol transport remains largely unknown.

Approach:

  • This review focuses on the PKA-dependent phosphorylation of StAR at specific serine residues (S194/195 in mouse/human StAR).
  • It examines the role of this phosphorylation, which is critical for StAR's function in steroidogenesis.
  • A model for StAR translation and phosphorylation at the outer mitochondrial membrane is presented.

Key Points:

  • PKA activation by ACTH leads to increased StAR expression and function.
Keywords:
ACTHStARadrenalphosphorylationtranslation

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  • StAR phosphorylation at S194/195 is a required modification for its role in steroidogenesis.
  • The outer mitochondrial membrane is identified as the site for StAR function and phosphorylation.

    • Conclusions:

    • Phosphorylation of StAR by PKA is a key regulatory event in steroidogenesis.
    • Understanding StAR phosphorylation provides insights into its mechanism of action in cholesterol transport.
    • A unified model for StAR function at the outer mitochondrial membrane is proposed.