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Phosphorylation of Ack1 by the Receptor Tyrosine Kinase Mer

Samantha Y Hayashi1, Barbara P Craddock1, W Todd Miller1,2

  • 1Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.

Kinases and Phosphatases
|September 4, 2023
PubMed

Insights

The receptor tyrosine kinase Mer activates Ack1 kinase through direct interaction. Mer preferentially phosphorylates Ack1

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Biochemistry

Background:

  • Ack1 (a nonreceptor tyrosine kinase) regulates cell proliferation and survival.
  • The TAM family receptor tyrosine kinase Mer is a known upstream activator of Ack1.
  • The precise mechanism linking Mer and Ack1 activation remained unelucidated.

Purpose of the Study:

  • To investigate the molecular mechanism by which Mer activates Ack1.
  • To characterize the interaction and phosphorylation events between Mer and Ack1.

Main Methods:

  • Co-immunoprecipitation experiments to confirm protein-protein interaction.
  • Kinase activity assays to assess Ack1 activation by Mer.
  • Site-directed mutagenesis of Mer and Ack1 to identify key residues.
  • Synthetic peptide analysis to determine phosphorylation site preference.

Main Results:

  • Mer and Ack1 were confirmed to interact, with Mer activity enhancing Ack1 activity.
  • Mer's kinase activity, but not specific C-terminal tyrosines (Y867, Y924), was crucial for Ack1 activation.
  • Mer preferentially phosphorylated a specific sequence within Ack1's Mig6 Homology Region (MHR), specifically targeting pY860 over pY859.
  • Mutational analysis supported a model of sequential phosphorylation within the Ack1 MHR.

Conclusions:

  • Mer directly interacts with and activates Ack1 kinase.
  • Mer-mediated phosphorylation of Ack1 occurs sequentially within the MHR, with a preference for pY860.
  • This Mer-Ack1 interaction may be significant in immune cell signaling and implicated in cancer hyperactivation.
Keywords:
Ack1MHRMerautoinhibitionphosphorylationtyrosine kinase

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