Yolk protein endocytosis by oocytes in Drosophila melanogaster: immunofluorescent localization of clathrin, adaptin and the yolk protein receptor.
Journal of Insect Physiology. 47/7,67-75, (2001)
David S. Richard *, Matthew Gilbert, Brandy Crum, Debra M. Hollinshead, Suzanne Schelble, Danielle Scheswohl.
Department of Biology, Susquehanna University, Selinsgrove, PA 17870, USA.
#Corresponding Author. Tel.: 570-372 -4206; Fax: 570-372-2751.
E-mail address: richard@susqu.edu (D.S. Richard)
Abstract
The process of yolk protein (YP) uptake by developing oocytes in Drosophila melanogaster has been investigated by immunofluorescent localization of the endocytosis proteins, clathrin, a-adaptin and the putative yolk protein receptor (YP receptor). Data suggests that YPs from the follicle cells are trafficked into the oocyte during early stages of vitellogenesis, and that hemolymph YPs are sequestered by nurse cells adjacent to the developing oocyte during late stages of vitellogenesis. Yolk proteins were immunolocalized to both follicle cells and nurse cells during these processes. Diapausing female Drosophila melanogaster undergo a pre-vitellogenic arrest of ovarian development associated with the absence of ovarian a-adaptin, clathrin and putative YP receptor. Diapause termination by transfer of whole animals from 11oC to 25oC, or by 20-hydroxyecdysone injection, results in the appearance of immunopositive material in the nurse cells for all three proteins between 12h and 16h post upshift and within 4 days of injection. Immunopositive material was not noted in the follicle cells during diapause termination. In vitro warming of diapausing ovaries, or incubation in the presence of 1mM 20hydroxyecdysone failed to initiate early vitellogenic development suggesting that diapause termination requires factor(s) external to the ovary. Western blotting analysis of extracts of 24 h post-eclosion wild type and ap56f females identified putative yolk protein receptor with a molecular weight of 208kDa and clathrin with a molecular weight of 178kDa.
Key words: a-adaptin, clathrin, Drosophila melanogaster, endocytosis, Vitellogenesis, yolk protein receptor