Synaptic scaffolding molecule binds to and regulates vasoactive intestinal polypeptide type-1 receptor in epithelial cells

Gastroenterology. 2009 Aug;137(2):607-17, 617.e1-4. doi: 10.1053/j.gastro.2009.01.065.


Background & aims: Vasoactive intestinal polypeptide (VIP) is a principal regulator of fluid and electrolyte secretion in the gastrointestinal system. The VIP type-1 receptor (VPAC1), a class II G-protein-coupled receptor, contains a putative C-terminal PDZ-binding motif. A yeast 2-hybrid screen indicated that the C-terminus of VPAC1 bound to the PDZ domain of synaptic scaffolding molecule (S-SCAM, also known as membrane-associated guanylate kinase inverted-2 [MAGI-2]). We analyzed the association between S-SCAM and VPAC1.

Methods: The biochemical properties and physiologic significance of the interaction between VPAC1 and S-SCAM were examined in heterologous expression systems, T84 colonic epithelial cells, and human pancreas and colon tissues using an integrated molecular and physiologic approach.

Results: The physical interaction between VPAC1 and S-SCAM was confirmed by immunoprecipitation in HEK 293 mammalian cells and human pancreatic and colonic tissues. Immunocytochemical analysis indicated that S-SCAM recruited VPAC1 to the junctional area near the apical end of the lateral membrane in T84 cells. Several lines of evidence revealed that S-SCAM inhibits VPAC1 activation. Overexpression of S-SCAM inhibited VPAC1-mediated cAMP production and agonist-induced VPAC1 internalization in HEK 293 and HeLa cells. In addition, S-SCAM decreased the VPAC1-mediated current through the cystic fibrosis transmembrane conductance regulator in Xenopus oocytes, especially at low concentrations of VIP. Importantly, loss of S-SCAM increased VIP-induced short-circuit currents in T84 monolayers, which endogenously express VPAC1 and S-SCAM.

Conclusions: S-SCAM/MAGI-2 interacts with and regulates VPAC1 intracellular localization in epithelial cells and inhibits VPAC1 agonist-induced activation and internalization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Analysis of Variance
  • Carrier Proteins
  • Cell Communication / genetics
  • Cell Communication / physiology
  • Cells, Cultured
  • Epithelial Cells / metabolism*
  • Epithelial Cells / physiology
  • Gene Expression Regulation
  • Guanylate Kinases
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Probability
  • Protein Binding / genetics
  • Protein Binding / physiology*
  • Receptors, Vasoactive Intestinal Polypeptide, Type I / genetics
  • Receptors, Vasoactive Intestinal Polypeptide, Type I / metabolism*
  • Signal Transduction / genetics
  • Two-Hybrid System Techniques


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Receptors, Vasoactive Intestinal Polypeptide, Type I
  • VIPR1 protein, human
  • Guanylate Kinases
  • MAGI2 protein, human