Protein kinase A-mediated phosphorylation of naked cuticle homolog 2 stimulates cell-surface delivery of transforming growth factor-α for epidermal growth factor receptor transactivation

Traffic. 2019 May;20(5):357-368. doi: 10.1111/tra.12642.


The classic mode of G protein-coupled receptor (GPCR)-mediated transactivation of the receptor tyrosine kinase epidermal growth factor receptor (EGFR) transactivation occurs via matrix metalloprotease (MMP)-mediated cleavage of plasma membrane-anchored EGFR ligands. Herein, we show that the Gαs-activating GPCR ligands vasoactive intestinal peptide (VIP) and prostaglandin E2 (PGE2 ) transactivate EGFR through increased cell-surface delivery of the EGFR ligand transforming growth factor-α (TGFα) in polarizing madin-darby canine kidney (MDCK) and Caco-2 cells. This is achieved by PKA-mediated phosphorylation of naked cuticle homolog 2 (NKD2), previously shown to bind TGFα and direct delivery of TGFα-containing vesicles to the basolateral surface of polarized epithelial cells. VIP and PGE2 rapidly activate protein kinase A (PKA) that then phosphorylates NKD2 at Ser-223, a process that is facilitated by the molecular scaffold A-kinase anchoring protein 12 (AKAP12). This phosphorylation stabilized NKD2, ensuring efficient cell-surface delivery of TGFα and increased EGFR activation. Thus, GPCR-triggered, PKA/AKAP12/NKD2-regulated targeting of TGFα to the cell surface represents a new mode of EGFR transactivation that occurs proximal to ligand cleavage by MMPs.

Keywords: A-kinase anchoring protein 12 (AKAP12); EGFR transactivation; G protein-coupled receptor (GPCR); epidermal growth factor receptor (EGFR); naked cuticle homolog 2 (NKD2); protein kinase A (PKA); transforming growth factor-α (TGFα).

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • A Kinase Anchor Proteins / metabolism
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Caco-2 Cells
  • Calcium-Binding Proteins / metabolism*
  • Cell Cycle Proteins / metabolism
  • Cell Membrane / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Dinoprostone / metabolism
  • Dogs
  • ErbB Receptors / metabolism
  • HEK293 Cells
  • Humans
  • Madin Darby Canine Kidney Cells
  • Protein Transport
  • Signal Transduction
  • Transforming Growth Factor alpha / metabolism*
  • Vasoactive Intestinal Peptide / metabolism


  • A Kinase Anchor Proteins
  • AKAP12 protein, human
  • Adaptor Proteins, Signal Transducing
  • Calcium-Binding Proteins
  • Cell Cycle Proteins
  • NKD2 protein, human
  • Transforming Growth Factor alpha
  • Vasoactive Intestinal Peptide
  • ErbB Receptors
  • Cyclic AMP-Dependent Protein Kinases
  • Dinoprostone