The conserved WW-domain binding sites in Dystroglycan C-terminus are essential but partially redundant for Dystroglycan function.

BACKGROUND: Dystroglycan (Dg) is a transmembrane protein that is a part of the Dystrophin Glycoprotein Complex (DGC) which connects the extracellular matrix to the actin cytoskeleton. The C-terminal end of Dg contains a number of putative SH3, SH2 and WW domain binding sites. The most C-terminal PPXY motif has been established as a binding site for Dystrophin (Dys) WW-domain. However, our previous studies indicate that both Dystroglycan PPXY motives, WWbsI and WWbsII can bind Dystrophin protein in vitro. RESULTS: We now find that both WW binding sites are important for maintaining full Dg function in the establishment of oocyte polarity in Drosophila. If either WW binding site is mutated, the Dg protein can still be active. However, simultaneous mutations in both WW binding sites abolish the Dg activities in both overexpression and loss-of-function oocyte polarity assays in vivo. Additionally, sequence comparisons of WW binding sites in 12 species of Drosophila, as well as in humans, reveal a high level of conservation. This preservation throughout evolution supports the idea that both WW binding sites are functionally required. CONCLUSION: Based on the obtained results we propose that the presence of the two WW binding sites in Dystroglycan secures the essential interaction between Dg and Dys and might further provide additional regulation for the cytoskeletal interactions of this complex.

[Genetic analysis of X-chromosome neurodegenerative mutants of Drosophila melanogaster induced by ethyl methansulfonate and nitrosoethylurea]. / Geneticheskii analiz neirodegenerativnykh mutantov Drosophila melanogaster po X-khromosome, indutsirovannykh étilmetansul'fonatom i nitrozoétilmochevinoi.

In a series of Drosophila mutants with changes in the brain structure, some characters (reduced life span, behavioral changes, and neuronal loss in various brain regions) resemble symptoms observed in human patients with neurodegenerative diseases. In addition, similar specific phenotypes shared by different species suggest that common mechanisms underlie degeneration of their nerve cell. This study reports the results of a genetic analysis of new X-chromosome mutants with neurodegenerative changes in brain structure, which were induced by chemical mutagenesis. According to complementation test, all mutants were divided into three complementation groups, in which the life span and dynamics of neurodegenerative changes were studied. The life span of Drosophila melanogaster flies was found to depend on the state of their nervous system.