Sphingosine kinase interacting protein is an A-kinase anchoring protein specific for type I cAMP-dependent protein kinase

Chembiochem. 2010 May 3;11(7):963-71. doi: 10.1002/cbic.201000058.


The compartmentalization of kinases and phosphatases plays an important role in the specificity of second-messenger-mediated signaling events. Localization of the cAMP-dependent protein kinase is mediated by interaction of its regulatory subunit (PKA-R) with the versatile family of A-kinase-anchoring proteins (AKAPs). Most AKAPs bind avidly to PKA-RII, while some have dual specificity for both PKA-RI and PKA-RII; however, no mammalian PKA-RI-specific AKAPs have thus far been assigned. This has mainly been attributed to the observation that PKA-RI is more cytosolic than the more heavily compartmentalized PKA-RII. Chemical proteomics screens of the cAMP interactome in mammalian heart tissue recently identified sphingosine kinase type 1-interacting protein (SKIP, SPHKAP) as a putative novel AKAP. Biochemical characterization now shows that SPHKAP can be considered as the first mammalian AKAP that preferentially binds to PKA-RIalpha. Recombinant human SPHKAP functions as an RI-specific AKAP that utilizes the characteristic AKAP amphipathic helix for interaction. Further chemical proteomic screening utilizing differential binding characteristics of specific cAMP resins confirms SPHKAPs endogenous specificity for PKA-RI directly in mammalian heart and spleen tissue. Immunolocalization studies revealed that recombinant SPHKAP is expressed in the cytoplasm, where PKA-RIalpha also mainly resides. Alignment of SPHKAPs' amphipathic helix with peptide models of PKA-RI- or PKA-RII-specific anchoring domains shows that it has largely only PKA-RIalpha characteristics. Being the first mammalian PKA-RI-specific AKAP with cytosolic localization, SPHKAP is a very promising model for studying the function of the less explored cytosolic PKA-RI signaling nodes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A Kinase Anchor Proteins / genetics
  • A Kinase Anchor Proteins / metabolism*
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Cell Line
  • Cyclic AMP / chemistry*
  • Cyclic AMP-Dependent Protein Kinase Type I / analysis
  • Cyclic AMP-Dependent Protein Kinase Type I / metabolism*
  • Heart Ventricles / enzymology
  • Humans
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment


  • A Kinase Anchor Proteins
  • Adaptor Proteins, Signal Transducing
  • Recombinant Proteins
  • SPHKAP protein, human
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinase Type I