COMPARATIVE STUDY OF Hrs AND OTHER ENDOSOMAL MARKERS CELLULAR LOCALIZATION IN DROSOPHILA MELANOGASTER SPERMATOGENESIS
BY GFP-CHIMERICAL PROTEIN APPROACH
E.V. Marilovtseva,1 T.D. Dubatolova,1 J.A. Galimova,1 S.A. Kopyl,1 L.V. Omelyanchuk 1,2
1 Institute of Molecular and Cellular Biology Siberian Branch of RAS, Novosibirsk, 630090,
and 2 Novosibirsk State University, Novosibirsk, 630090;
2 e-mail:ome@mcb.nsc.ru
Acrosome is a special organelle in spermatozoids necessary for fertilizing oocyte and originates, according
to various theories, either from Golgi apparatus, or from endosomes and lysosomes. One of the proteins, found
at mammalian acrosome, is Hgs, a homologue of Drosophila melanogaster Hrs (Hepatocyte growth factor regulated
tyrosine kinase substrate), a known marker of multivesicular bodies (MVBs). However, although Drosophila
acrosome was extensively studied, it is yet unknown whether Hrs localizes at acrosome similar to Hgs
and, more generally, whether the spectrum of acrosomal proteins in Drosophila is the same as in mammals. Hrs
(hepatocyte growth factor regulated tyrosine kinase substrate) is the multidomain vesicular protein participating
in the endosome-lysosome protein sorting. We demonstrated that two protein variants of the Drosophila Hrs are
expressed in testes: a longer isoform B, and a shorter isoform A, which lacks VHS and FYVE domains that are
necessary for anchoring Hrs in endosomes. We found that Hrs isoform B is concentrated at fusoma of spermatocytes
in contrast to mammalian Hrs. This localization requires the C-terminus of the protein, starting from the
aminoacid residue 383. In situ hybridization of hrs RNA probe showed that the gene is expressed early in spermatogenesis
consistently with Hrs localization in early fusoma. Additionally, we demonstrated that Hrs is dispensable
for cytokinesis. Finally, it was found that although Drosophila Hrs does not localize at acrosome, the
other endosomal markers — Rab4, Rab7, and Rab11 — are detected at the organelle.
Key words:
vesilular traffic, endosome, endocytosis, spermatogenesis, acrosome, fusome
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