The C-terminus of the transmembrane mucin MUC17 binds to the scaffold protein PDZK1 that stably localizes it to the enterocyte apical membrane in the small intestine.
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 of PDZ-domain-binding proteins. To identify PDZ proteins that are able to interact with the mucins,we screened PDZ domain arrays using YFP (yellow fluorescent protein)-tagged proteins. MUC17 exhibited a strong binding to PDZK1 (PDZ domain containing 1), whereas the binding toNHERF1 (Na+/H+-exchanger regulatory factor 1) was weak.Furthermore, we showed weak binding of MUC12 to PDZK1, NHERF1 and NHERF2. GST (glutathione transferase) pull-down experiments confirmed that the C-terminal tail of MUC17 coprecipitates with the scaffold protein PDZK1 as identified byMS. 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 brushborder membrane staining in the wild-type mice compared with 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.
Malmberg
Emily K
EK
Department of Medical Biochemistry and Cell Biology, Göteborg University, 413 90 Gothenburg, Sweden.
Pelaseyed
Thaher
T
Petersson
Asa C
AC
Seidler
Ursula E
UE
De Jonge
Hugo
H
Riordan
John R
JR
Hansson
Gunnar C
GC
D000230:Adenocarcinoma; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D003110:Colonic Neoplasms; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism; D007668:Kidney; D008565:Membrane Proteins; D008647:Mesocricetus; D008871:Microvilli / Q000378:metabolism; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
D002352:Carrier Proteins; D017931:DNA Primers; C450720:MUC17 protein, human; D008565:Membrane Proteins; D009077:Mucins; C484659:PDZK1 protein, human; D011994:Recombinant Proteins