Nucleoside analogue activators of cyclic AMP-independent protein kinase A of Trypanosoma

Nat Commun. 2019 Mar 29;10(1):1421. doi: 10.1038/s41467-019-09338-z.

Abstract

Protein kinase A (PKA), the main effector of cAMP in eukaryotes, is a paradigm for the mechanisms of ligand-dependent and allosteric regulation in signalling. Here we report the orthologous but cAMP-independent PKA of the protozoan Trypanosoma and identify 7-deaza-nucleosides as potent activators (EC50 ≥ 6.5 nM) and high affinity ligands (KD ≥ 8 nM). A co-crystal structure of trypanosome PKA with 7-cyano-7-deazainosine and molecular docking show how substitution of key amino acids in both CNB domains of the regulatory subunit and its unique C-terminal αD helix account for this ligand swap between trypanosome PKA and canonical cAMP-dependent PKAs. We propose nucleoside-related endogenous activators of Trypanosoma brucei PKA (TbPKA). The existence of eukaryotic CNB domains not associated with binding of cyclic nucleotides suggests that orphan CNB domains in other eukaryotes may bind undiscovered signalling molecules. Phosphoproteome analysis validates 7-cyano-7-deazainosine as powerful cell-permeable inducer to explore cAMP-independent PKA signalling in medically important neglected pathogens.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / chemistry
  • Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / metabolism*
  • Dipyridamole / pharmacology
  • Drug Evaluation, Preclinical
  • Enzyme Activators / chemistry
  • Enzyme Activators / pharmacology*
  • Holoenzymes / metabolism
  • Leishmania / drug effects
  • Molecular Docking Simulation
  • Nucleosides / analogs & derivatives*
  • Phosphorylation / drug effects
  • Signal Transduction
  • Trypanosoma brucei brucei / drug effects
  • Trypanosoma brucei brucei / enzymology*
  • Tubercidin / pharmacology

Substances

  • Cyclic AMP-Dependent Protein Kinase RIalpha Subunit
  • Enzyme Activators
  • Holoenzymes
  • Nucleosides
  • Dipyridamole
  • Cyclic AMP
  • Tubercidin