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Rabin8 Protein Interacts with GTPase Rheb and Inhibits Phosphorylation of Ser235/Ser236 in Small Ribosomal Subunit

Capital A Cyrillic А Parkhitko1, Capital O Cyrillic О Favorova, E P Henske

  • 1Pirogov Russian National Research Medical University.

Acta Naturae
|June 1, 2012
PubMed

Insights

Rabin8, a guanine nucleotide exchange factor, regulates the mammalian target of rapamycin complex 1 (mTORC1) pathway by affecting ribosomal protein S6 phosphorylation. This suggests a novel link between Rheb/mTORC1 and ciliogenesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is crucial for regulating protein biosynthesis, metabolism, and autophagy.
  • mTORC1 activation is mediated by growth factors and amino acids through Rheb GTPase.
  • Ribosomal protein S6 phosphorylation is a key downstream event regulated by mTORC1.

Purpose of the Study:

  • To investigate the role of Rabin8, a guanine nucleotide exchange factor for Rab8 GTPase, in mTORC1 regulation.
  • To explore the potential interaction between Rabin8, Rheb GTPase, and mTORC1 signaling.
  • To determine if Rabin8 influences ciliogenesis through Rheb/mTORC1 pathways.

Main Methods:

  • Over-expression of Rabin8 in cells.
  • Downregulation of Rabin8 using small interfering RNA (siRNA).
  • Immunoprecipitation assays to detect protein interactions.
  • Western blotting to assess phosphorylation levels of ribosomal protein S6.

Main Results:

  • Over-expression of Rabin8 suppressed the phosphorylation of ribosomal protein S6 (Ser235/Ser236).
  • Downregulation of Rabin8 using siRNA increased ribosomal protein S6 phosphorylation.
  • Rabin8 was successfully immunoprecipitated with Rheb GTPase, indicating a physical interaction.
  • These findings suggest a novel regulatory mechanism for mTORC1.

Conclusions:

  • Rabin8 plays a significant role in regulating mTORC1 activity, specifically impacting ribosomal protein S6 phosphorylation.
  • A novel interaction between Rabin8 and Rheb GTPase has been identified, suggesting a new pathway for mTORC1 control.
  • The study proposes a potential connection between Rheb/mTORC1 regulation and ciliogenesis, given Rabin8's known role in the latter.
Keywords:
Rabin8Rhebcomplex mTORC1small ribosomal unit protein S6

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