The C-terminus of the transmembrane MUC17 mucin binds to the scaffold protein PDZK1 that stably localizes it to the enterocyte apical membrane in the small intestine

Emily K Malmberg , Thaher Pelaseyed , Åsa Petersson , Ursula E. Seidler , Hugo R. de Jonge , John R. Riordan , Gunnar C. Hansson (1)

1 Medical Biochemistry

The membrane bound mucins have a heavily O-glycosylated extracellular domain, a single pass membrane domain and a short cytoplasmic tail. Three of the membrane bound mucins, MUC3, MUC12 and MUC17, are clustered on chromosome 7 and found in the gastrointestinal tract. These mucins have C-terminal sequences typical for PDZ domain binding proteins. To identify PDZ proteins able to interact with the mucins, we screened PDZ domain arrays using YFP-tagged proteins. MUC17 exhibited a strong binding to PDZK1 whereas the binding to NHERF1 was weak. Furthermore, we showed weak binding of MUC12 to PDZK1, NHERF1 and NHERF2. GST pull-down experiments confirmed that the C-terminal tail of MUC17 co-precipitates with the scaffold protein PDZK1 as identified by mass spectrometry. This was mediated through the C-terminal PDZ-interaction site in MUC17 which was capable of binding to three of the four PDZ domains in PDZK1. Immunostaining of wild-type or Pdzk1-/- mouse jejunum with an antiserum against Muc3(17), the mouse orthologue of human MUC17, revealed strong brush border membrane staining in the wild-type mice compared to an intracellular Muc3(17) staining in the Pdzk1-/- mice. This suggests that Pdzk1 plays a specific role in stabilizing Muc3(17) in the apical membrane of small intestinal enterocytes.

Mots clés: Life Sciences

Emily K Malmberg, Thaher Pelaseyed, Åsa Petersson, Ursula E. Seidler, Hugo R. de Jonge, et al.. The C-terminus of the transmembrane MUC17 mucin binds to the scaffold protein PDZK1 that stably localizes it to the enterocyte apical membrane in the small intestine. Biochemical Journal, 2008, 410 (2), pp.283-289. ⟨10.1042/BJ20071068⟩. ⟨hal-00478867⟩