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Cell Mol Life Sci. 2009 Dec;66(24):3951-66. doi: 10.1007/s00018-009-0156-6. Epub 2009 Sep 22.

The PDZ2 domain of zonula occludens-1 and -2 is a phosphoinositide binding domain.

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  • 1Department of Medical Protein Research, VIB, 9000 Ghent, Belgium.

Abstract

Zonula occludens proteins (ZO) are postsynaptic density protein-95 discs large-zonula occludens (PDZ) domain-containing proteins that play a fundamental role in the assembly of tight junctions and establishment of cell polarity. Here, we show that the second PDZ domain of ZO-1 and ZO-2 binds phosphoinositides (PtdInsP) and we identified critical residues involved in the interaction. Furthermore, peptide and PtdInsP binding of ZO PDZ2 domains are mutually exclusive. Although lipid binding does not seem to be required for plasma membrane localisation of ZO-1, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P (2)) binding to the PDZ2 domain of ZO-2 regulates ZO-2 recruitment to nuclear speckles. Knockdown of ZO-2 expression disrupts speckle morphology, indicating that ZO-2 might play an active role in formation and stabilisation of these subnuclear structures. This study shows for the first time that ZO isoforms bind PtdInsPs and offers an alternative regulatory mechanism for the formation and stabilisation of protein complexes in the nucleus.

PMID:
19784548
[PubMed - indexed for MEDLINE]
PMCID:
PMC3724457
Free PMC Article
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