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Connexin43 PDZ2 binding domain mutants create functional gap junctions and exhibit altered phosphorylation
Chengshi Jin1, Kendra D Martyn, Wendy E Kurata
1Molecular Carcinogenesis Section, Cancer Research Center, Honolulu, Hawaii, 96813, USA.
Cell Communication & Adhesion
|October 26, 2005
Summary
The interaction between Connexin43 (Cx43) and zona occludens 1 (ZO-1) protein is crucial for regulating Cx43 phosphorylation. Disrupting this Cx43-ZO-1 binding affects Cx43 phosphorylation patterns.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Connexin43 (Cx43) is a key gap junction protein involved in intercellular communication.
- The C-terminal tail of Cx43 plays a vital role in regulating its function through protein interactions and phosphorylation.
- Zona occludens 1 (ZO-1) is a protein associated with tight and adherens junctions, known to interact with Cx43.
Purpose of the Study:
- To investigate the functional significance of the interaction between Cx43 and ZO-1.
- To determine how disrupting the Cx43-ZO-1 binding affects Cx43 localization, gap junction function, and phosphorylation.
- To elucidate the role of the Cx43 C-terminus in mediating interactions with ZO-1.
Main Methods:
- Utilizing Cx43-deficient MDCK cell lines expressing wild-type Cx43 (Cx43wt) and Cx43 mutants (Cx43deltaI382, Cx43delta378-382) lacking ZO-1 binding domains.
- Performing in vitro binding studies and coimmunoprecipitation assays to assess Cx43-ZO-1 interaction.
- Employing confocal and deconvolution microscopy to analyze protein localization and colocalization.
- Evaluating gap junction channel function and protein turnover rates.
Main Results:
- Cx43 mutants designed to disrupt ZO-1 binding failed to interact with ZO-1 in vitro and in coimmunoprecipitation assays.
- Both wild-type Cx43 and the mutants localized to the plasma membrane and formed functional gap junction channels.
- While protein turnover rates were similar, Cx43 mutants showed significantly reduced levels of P2 and P3 phosphoisoforms compared to Cx43wt.
- Cx43wt showed partial colocalization with ZO-1 at the plasma membrane, a pattern not observed with the mutants.
Conclusions:
- The interaction between Cx43 and ZO-1 is not essential for Cx43 plasma membrane targeting or gap junction channel formation.
- Disruption of the Cx43-ZO-1 interaction significantly impacts Cx43 phosphorylation, suggesting a regulatory role for ZO-1 in this process.
- The C-terminal binding domain of Cx43 is critical for its interaction with ZO-1, influencing Cx43 phosphorylation status.