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Sci Signal. 2018 Feb 13;11(517). pii: eaam9899. doi: 10.1126/scisignal.aam9899.

Structural basis for the interaction between the cell polarity proteins Par3 and Par6.

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Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany.
Molecular and Cellular Anatomy, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.
Medical Clinic D, University Hospital of Münster, Domagkstraβe 3a, 48149 Münster, Germany.
Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany.


Polarity is a fundamental property of most cell types. The Par protein complex is a major driving force in generating asymmetrically localized protein networks and consists of atypical protein kinase C (aPKC), Par3, and Par6. Dysfunction of this complex causes developmental abnormalities and diseases such as cancer. We identified a PDZ domain-binding motif in Par6 that was essential for its interaction with Par3 in vitro and for Par3-mediated membrane localization of Par6 in cultured cells. In fly embryos, we observed that the PDZ domain-binding motif was functionally redundant with the PDZ domain in targeting Par6 to the cortex of epithelial cells. Our structural analyses by x-ray crystallography and NMR spectroscopy showed that both the PDZ1 and PDZ3 domains but not the PDZ2 domain in Par3 engaged in a canonical interaction with the PDZ domain-binding motif in Par6. Par3 thus has the potential to recruit two Par6 proteins simultaneously, which may facilitate the assembly of polarity protein networks through multivalent PDZ domain interactions.


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