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Knocking down raptor in human keratinocytes affects ornithine decarboxylase in a post-transcriptional Manner

Coryn L Stump1, Robert P Feehan2, Torey Jordan1

  • 1Division of Science, The Pennsylvania State University Berks Campus, Reading, PA, 19610, USA.

Amino Acids
|April 12, 2019
PubMed

Insights

This study reveals that mammalian target of rapamycin complex 1 (mTORC1) activity regulates ornithine decarboxylase (ODC) mRNA stability in human keratinocytes following ultraviolet-B (UVB) exposure, a key factor in non-melanoma skin cancer development.

Area of Science:

  • Dermatology
  • Molecular Biology
  • Cancer Research

Background:

  • Non-melanoma skin cancer (NMSC) is the most common cancer, with ultraviolet-B (UVB) radiation as a known carcinogen.
  • Both mammalian target of rapamycin complex 1 (mTORC1) and ornithine decarboxylase (ODC) are upregulated by UVB, but their interaction is not fully understood.

Purpose of the Study:

  • To investigate the dependency of UVB-induced ornithine decarboxylase (ODC) upregulation on mammalian target of rapamycin complex 1 (mTORC1) in human keratinocytes.
  • To elucidate the role of mTORC1 in regulating ODC mRNA stability after UVB exposure.

Main Methods:

  • Comparison of mRNA stability in normal HaCaT cells versus HaCaT cells with reduced raptor (mTORC1 component) expression.
  • Assessment of ODC protein and mRNA levels before and after UVB irradiation.
  • Analysis of ODC mRNA translation initiation using polysome profiling.
  • Investigation of human antigen R (HuR) localization and function in ODC mRNA regulation via CRISPR/Cas9 ablation.

Main Results:

  • Knockdown of mTORC1 activity decreased ODC protein levels and reduced ODC mRNA stability post-UVB exposure.
  • UVB exposure increased cytoplasmic localization of HuR, but HuR ablation did not affect ODC mRNA stability.
  • Translation initiation of ODC mRNA was not altered by UVB treatment.

Conclusions:

  • UVB-induced ODC upregulation in human keratinocytes is partially dependent on mTORC1.
  • mTORC1 influences ODC mRNA stability, suggesting a regulatory mechanism independent of translation initiation or HuR.
  • These findings highlight a novel mTORC1-dependent pathway regulating ODC mRNA stability in response to UVB radiation.
Keywords:
Ornithine decarboxylasePost-transcriptional regulationmRNA stabilitymTOR

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