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Updated: May 11, 2026
06:45
Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Published on: May 26, 2011
Multiple motifs regulate apical sorting of p75 via a mechanism that involves dimerization and higher-order
Robert T Youker1, Jennifer R Bruns, Simone A Costa
1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA. rty4@pitt.edu
Molecular Biology of the Cell
|May 3, 2013
Summary
Protein clustering in the trans-Golgi network is crucial for apical sorting of p75. However, this clustering alone is insufficient to override strong basolateral signals for proper protein targeting.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Trafficking
Background:
- Polarized epithelial cells utilize complex sorting signals for apical protein delivery.
- The neurotrophin receptor p75's apical sorting depends on its O-glycosylated stalk, but the mechanism remains unclear.
- Protein oligomerization is a proposed mechanism for apical protein segregation.
Purpose of the Study:
- To investigate the role of p75 oligomerization and its stalk domain in apical sorting.
- To determine if protein clustering is a prerequisite for apical delivery.
- To elucidate the hierarchy of sorting signals in polarized protein transport.
Main Methods:
- Utilized fluorescence fluctuation techniques (photon-counting histogram and number/brightness analyses) to assess p75 oligomerization in vivo.
- Studied wild-type p75 and mutants with disrupted dimerization or stalk domains.
- Manipulated O-glycan processing and galectin levels, and analyzed a mutant with a dominant basolateral determinant.
Main Results:
- Wild-type p75 forms clusters in the trans-Golgi network (TGN), but not at the plasma membrane.
- Disruption of dimerization or stalk motifs impaired both p75 clustering and polarized delivery.
- O-glycan manipulation and galectin depletion did not affect p75 sorting.
- A mutant with a dominant basolateral determinant failed to oligomerize, and restoring dimerization did not rescue apical sorting.
Conclusions:
- Clustering in the TGN is required for the normal biosynthetic apical sorting of p75.
- Clustering is necessary but not sufficient for apical sorting when a strong basolateral determinant is present.
- The stalk domain likely acts structurally to facilitate lumenal domain interactions for oligomerization.
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