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Defective internal allosteric network imparts dysfunctional ATP/substrate-binding cooperativity in oncogenic chimera

Cristina Olivieri1, Caitlin Walker1, Adak Karamafrooz1

  • 1Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA.

Communications Biology
|March 11, 2021
PubMed

Insights

The DNAJB1-PRKACA gene fusion creates a chimeric protein kinase that drives fibrolamellar hepatocellular carcinoma. This chimera exhibits reduced allosteric cooperativity, disrupting normal cellular signaling pathways.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Aberrant gene fusions, such as DNAJB1-PRKACA, can lead to oncogenic protein kinases.
  • The chimeric protein kinase PKA-CDNAJB1 is implicated in fibrolamellar hepatocellular carcinoma (FL-HCC) and other cancers.
  • Understanding the molecular mechanisms of PKA-CDNAJB1 is crucial for developing targeted therapies.

Purpose of the Study:

  • To investigate the allosteric regulation of the PKA-CDNAJB1 chimera.
  • To determine how the J-domain fusion affects nucleotide and pseudo-substrate binding.
  • To elucidate the molecular basis for the oncogenic activity of PKA-CDNAJB1.

Main Methods:

  • Biochemical assays to assess kinase activity and substrate phosphorylation.
  • Analysis of allosteric responses to nucleotide and inhibitor binding.
  • Structural and biophysical methods to probe protein-protein interactions.

Main Results:

  • The PKA-CDNAJB1 chimera retains apparent functionality, phosphorylating substrates and interacting with regulatory partners.
  • Fusion of the DNAJB1 J-domain to PKA-C disrupts the kinase's internal allosteric network.
  • A significant attenuation of nucleotide and protein kinase inhibitor 1 (PKI) binding cooperativity was observed.

Conclusions:

  • The PKA-CDNAJB1 chimera exhibits altered allosteric regulation compared to wild-type PKA-C.
  • Reduced allosteric cooperativity likely contributes to the chimera's oncogenic potential by dysregulating substrate recognition and signaling.
  • These findings provide insights into the molecular mechanisms driving FL-HCC and suggest potential therapeutic targets.

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