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Defective organellar membrane protein trafficking in Ap3b1-deficient cells
1Departments of Human Genetics and Pathology, University of Utah, Salt Lake City, UT 84112, USA.
Journal of Cell Science
|November 1, 2000
Summary
Mutation of the Ap3b1 gene causes the pearl mouse phenotype, affecting intracellular transport. This study confirms Ap3b1 as the causal gene and reveals mislocalization of key proteins in affected cells.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- The AP-3 complex is crucial for intracellular vesicle transport.
- Alterations in Ap3b1, encoding the AP-3 beta3A subunit, are linked to the pearl mouse phenotype.
Purpose of the Study:
- To genetically confirm Ap3b1 as the cause of the pearl phenotype.
- To characterize the null phenotype of the Ap3b1 gene.
- To investigate the role of AP-3 in protein trafficking.
Main Methods:
- Gene disruption of Ap3b1 via homologous recombination in mice.
- Phenotypic analysis of homozygous and compound heterozygous mice.
- Immunofluorescence studies on cultured fibroblasts and melanocytes.
Main Results:
- Ap3b1 disruption recapitulated the pearl mouse phenotype.
- Homozygous Ap3b1(LN) mice exhibited lighter coat color and reduced AP-3 subunit accumulation compared to pearl mice, suggesting pearl is a hypomorph.
- Lysosomal proteins (Lamp I, Lamp II) and melanosomal protein (tyrosinase) were mislocalized in Ap3b1(LN) homozygotes, with Lamp proteins accumulating on the cell surface.
Conclusions:
- Ap3b1 is the causative gene for the pearl mouse phenotype.
- The findings support an alternative protein transport pathway via the plasma membrane mediated by AP-3.
- This research elucidates AP-3's role in lysosomal and melanosomal protein trafficking.