Defective expression of the mu3 subunit of the AP-3 adaptor complex in the Drosophila pigmentation mutant carmine |
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Authors: | Mullins C Hartnell L M Wassarman D A Bonifacino J S |
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Institution: | (1) Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, Building 18T/Room 101, National Institutes of Health, Bethesda, MD 20892, USA e-mail: juan@helix.nih.gov Tel.: +1-301-4966368, Fax: +1-301-4020078, US |
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Abstract: | The adaptor protein (AP) complexes AP-1, AP-2, and AP-3 mediate coated vesicle formation and sorting of integral membrane
proteins in the endocytic and late exocytic pathways in mammalian cells. A search of the Drosophila melanogaster expressed sequence tag (EST) database identified orthologs of family members mammalian medium (μ) chain families μ1, μ2,
and μ3, of the corresponding AP complexes, and δ-COP, the analogous component of the coatomer (COPI) complex. The Drosophila
orthologs exhibit a high degree of sequence identity to mammalian medium chain and δ-COP proteins. Northern analysis demonstrated
that medium chain and δ-COP mRNAs are expressed uniformly throughout fly development. Medium chain and δ-COP genes were cytologically
mapped and the μ3 gene was found to localize to a region containing the pigmentation locus carmine (cm). Analysis of genomic DNA of the cm
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mutant allele indicated the presence of a large insertion in the coding region of the μ3 gene and Northern analysis revealed
no detectable μ3 mRNA. Light microscopy of the cm
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mutant showed a reduction in primary, secondary, and tertiary pigment granules in the adult eye. These findings provide evidence
of a role for μ3 in the sorting processes required for pigment granule biogenesis in Drosophila.
Received: 7 June 1999 / Accepted: 4 July 1999 |
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Keywords: | Clathrin Sorting Tyrosine-based signal Pigment Hermansky-Pudlak syndrome |
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