Intrinsic disorder within AKAP79 fine-tunes anchored phosphatase activity toward substrates and drug sensitivity

Elife. 2017 Oct 2;6:e30872. doi: 10.7554/eLife.30872.

Abstract

Scaffolding the calcium/calmodulin-dependent phosphatase 2B (PP2B, calcineurin) focuses and insulates termination of local second messenger responses. Conformational flexibility in regions of intrinsic disorder within A-kinase anchoring protein 79 (AKAP79) delineates PP2B access to phosphoproteins. Structural analysis by negative-stain electron microscopy (EM) reveals an ensemble of dormant AKAP79-PP2B configurations varying in particle length from 160 to 240 Å. A short-linear interaction motif between residues 337-343 of AKAP79 is the sole PP2B-anchoring determinant sustaining these diverse topologies. Activation with Ca2+/calmodulin engages additional interactive surfaces and condenses these conformational variants into a uniform population with mean length 178 ± 17 Å. This includes a Leu-Lys-Ile-Pro sequence (residues 125-128 of AKAP79) that occupies a binding pocket on PP2B utilized by the immunosuppressive drug cyclosporin. Live-cell imaging with fluorescent activity-sensors infers that this region fine-tunes calcium responsiveness and drug sensitivity of the anchored phosphatase.

Keywords: AKAP79; anchoring proteins; biochemistry; calcineurin/PP2B; calcium signaling; intrinsic disorder; short linear motifs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A Kinase Anchor Proteins / chemistry*
  • A Kinase Anchor Proteins / metabolism*
  • Calcineurin / chemistry*
  • Calcineurin / metabolism*
  • Calcium / metabolism
  • Calmodulin / metabolism
  • Humans
  • Microscopy, Electron
  • Protein Binding
  • Protein Conformation
  • Protein Interaction Maps

Substances

  • A Kinase Anchor Proteins
  • AKAP5 protein, human
  • Calmodulin
  • Calcineurin
  • Calcium