Claudin-8 interacts with multi-PDZ domain protein 1 (MUPP1) and reduces paracellular conductance in epithelial cells
Jeansonne, B.; Lu, Q.; Goodenough, D.A.; Chen, Y.H.
Cellular and Molecular Biology 49(1): 13-21
2003
ISSN/ISBN: 0145-5680 PMID: 12839333 Document Number: 554234
The claudin family is a set of integral membrane proteins found at cell-cell interactions in tight junctions. To identify proteins that interact with claudin-8, we used the yeast two-hybrid system to search for binding partners. Using the C-terminal 37 amino acids of claudin-8 as bait, we screened a human kidney cDNA library and identified multi-PDZ domain protein 1 (MUPP1) as a claudin-8 binding protein. MUPP1 contains 13 PDZ domains and binds to claudin-8 through its PDZ9 domain. When MDCK cells were transfected with epitope-tagged claudin-8 or MUPP1, both molecules were concentrated at cell-cell junctions. The interaction of claudin-8 and MUPP1 in vivo was confirmed by co-immunolocalization and co-immunoprecipitation in MDCK cells. Expression of claudin-8-myc increased transepithelial electrical resistance (TER) and reduced paracellular flux using FITC-dextran as a tracer. Over-expression of FLAG-MUPP1 in MDCK cells also reduced the epithelial paracellular conductance. Our results indicate that claudin-8 and MUPP1 interact in tight junctions of epithelial cells and are involved in the tight junction barrier function.