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Mammalian lin-7 stabilizes polarity protein complexes

Samuel W Straight1, Jay N Pieczynski, Eileen L Whiteman

  • 1Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.

The Journal of Biological Chemistry
|October 3, 2006
PubMed

Insights

Mammalian Lin-7 protein is crucial for maintaining tight junctions in epithelial cells. Its absence leads to PALS1 protein instability, disrupting cell polarity and barrier function.

Area of Science:

  • Cell Biology
  • Epithelial Biology
  • Protein Interactions

Background:

  • Mammalian Lin-7 protein complexes are involved in determining epithelial cell polarity.
  • Lin-7 interacts with proteins like PALS1, crucial for cell structure and function.

Purpose of the Study:

  • To investigate the role of Lin-7 in maintaining tight junction formation and protein stability in polarized epithelial cells.
  • To identify the specific domains of Lin-7 and its binding partners essential for its function.

Main Methods:

  • Utilized small hairpin RNA (shRNA) to knock down Lin-7 expression in Madin-Darby canine kidney II cells.
  • Assessed tight junction integrity via transepithelial electrical resistance (TEER) measurements and ZO-1 protein localization.
  • Performed rescue experiments using exogenous expression of Lin-7 constructs and PALS1.

Main Results:

  • Lin-7 knockdown caused defects in tight junction formation, indicated by reduced TEER and ZO-1 mislocalization.
  • Loss of Lin-7 led to decreased expression of binding partners PALS1 and PATJ.
  • Exogenous expression of Lin-7's L27 domain or PALS1 rescued the observed defects, restoring PATJ levels.
  • Lin-7 knockdown resulted in PALS1 protein instability and increased degradation.

Conclusions:

  • Mammalian Lin-7 stabilizes PALS1 protein, which is essential for maintaining tight junction integrity in epithelial cells.
  • Lin-7's L27 domain is critical for its function in stabilizing PALS1 and preserving cell polarity.
  • Lin-7 plays a vital role in epithelial barrier function through PALS1 stabilization.

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