Abstract
yata mutants of Drosophila melanogaster exhibit phenotypes including progressive brain shrinkage, developmental abnormalities and shortened lifespan, whereas in mammals, null mutations of the yata ortholog Scyl1 result in motor neuron degeneration. yata mutation also causes defects in the anterograde intracellular trafficking of a subset of proteins including APPL, which is the Drosophila ortholog of mammalian APP, a causative molecule in Alzheimer's disease. SCYL1 binds and regulates the function of coat protein complex I (COPI) in secretory vesicles. Here, we reveal a role for the Drosophila YATA protein in the proper localization of COPI. Immunohistochemical analyses performed using confocal microscopy and structured illumination microscopy showed that YATA colocalizes with COPI and GM130, a cis-Golgi marker. Analyses using transgenically expressed YATA with a modified N-terminal sequence revealed that the N-terminal portion of YATA is required for the proper subcellular localization of YATA. Analysis using transgenically expressed YATA proteins in which the C-terminal sequence was modified revealed a function for the C-terminal portion of YATA in the subcellular localization of COPI. Notably, when YATA was mislocalized, it also caused the mislocalization of COPI, indicating that YATA plays a role in directing COPI to the proper subcellular site. Moreover, when both YATA and COPI were mislocalized, the staining pattern of GM130 revealed Golgi with abnormal elongated shapes. Thus, our in vivo data indicate that YATA plays a role in the proper subcellular localization of COPI.
Highlights
In eukaryotic cells, transmembrane proteins and secreted proteins are synthesized in the rough endoplasmic reticulum (ER) and transported to their own destinations by intracellular vesicular trafficking (Bonifacino and Glick, 2004)
YATA colocalizes with complex I (COPI) and a cis-Golgi marker To assess the molecular function of the YATA protein, we examined its subcellular localization using an antiYATA antibody
We examined pupal brains 72 h after puparium formation because this is the stage at which impaired anterograde trafficking of the APPL protein and aberrant accumulation of COPII were previously observed in yata mutants (Sone et al, 2009)
Summary
Transmembrane proteins and secreted proteins are synthesized in the rough endoplasmic reticulum (ER) and transported to their own destinations by intracellular vesicular trafficking (Bonifacino and Glick, 2004). We previously identified a Drosophila yata mutant that showed phenotypes in the compound eye, wing and brain (Sone et al, 2009). Homozygotes of the null allele of the yata gene, yataKE2.1, show various phenotypes such as morphological abnormalities in the compound eye and wing, progressive reduction of brain volume and shortened lifespan. Electron microscopic examination of the internal morphology of the compound eye revealed that the yata mutation enhanced the formation of an abnormal cellular structure that formed as a bleb-like cellular protrusion and contained membranous organelles that had the appearance of lysosomes, autophagosomes and late endosomes (Arimoto et al, 2020). It encodes a protein that has no transmembrane domains and has a catalytic domain of a protein kinase
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