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Two classes of tight junctions are revealed by ZO-1 isoforms
1Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
The American Journal of Physiology
|April 1, 1993
Summary
Two isoforms of the tight junction protein ZO-1 (zonula occludens-1) show distinct tissue distributions. The ZO-1 alpha- isoform is found in dynamic junctions, while ZO-1 alpha+ is in less dynamic ones, impacting barrier regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Physiology
Background:
- Tight junctions form crucial intercellular barriers in epithelia and endothelia.
- Their diverse characteristics are not fully understood at the molecular level.
- Two ZO-1 (zonula occludens-1) protein isoforms arise from alternative RNA splicing.
Purpose of the Study:
- To investigate the differential distribution of ZO-1 isoforms in various tissues.
- To correlate ZO-1 isoform expression with tight junction characteristics.
- To understand the implications for paracellular barrier regulation.
Main Methods:
- Utilized isoform-specific antibodies and double-labeled immunofluorescence microscopy.
- Performed immunoblotting and ribonuclease protection assays.
- Analyzed ZO-1 expression patterns in diverse epithelial and endothelial cells.
Main Results:
- The ZO-1 alpha- isoform is specifically found in endothelial cells and specialized epithelial cells (Sertoli cells, podocytes).
- The ZO-1 alpha+ isoform is expressed in all other examined epithelial cells.
- Expression patterns correlate with junctional plasticity, not resistance or ultrastructure.
Conclusions:
- This study reveals the first molecular distinction between tight junction types based on ZO-1 isoforms.
- The findings suggest a fundamental dichotomy in tight junction regulation between endothelia and epithelia.
- Differential expression of ZO-1 isoforms impacts the plasticity and regulation of paracellular barriers.