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A fat body derived protein is selectively sulfated in the stick insect ovary by transcytosis through the follicular epithelium
Author(s) -
Giorgi Franco,
Falleni Alessandra,
Cecchettini Antonella,
Gremigni Vittorio
Publication year - 1998
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/s0248-4900(98)80339-0
Subject(s) - transcytosis , immunogold labelling , biology , microbiology and biotechnology , golgi apparatus , epithelium , vesicle , vesicular transport protein , basal lamina , oocyte , biochemistry , endocytosis , endoplasmic reticulum , anatomy , ultrastructure , cell , membrane , genetics , embryo
With the onset of vitellogenesis, the follicular epithelium overlying the oocyte in stick insect ovarioles becomes highly polarized and patent by formation of wide intercellular spaces. The aim of the present study was to provide experimental support to the notion that the follicular epithelium in this insect species may be involved in transcytosis. Data demonstrate that the follicular epithelium carries out sulfo‐conjugation of a 85 kDa fat body derived protein by allowing it to transit from one cell pole to another. Along the basal end, follicle cells branch into a number of cytoplasmic finger‐like projections. At the opposite end facing the oocyte they taper off into lance‐head shapes. Different vesicular elements are evident at both these extremities. In vivo exposure to horseradish peroxidase shows that the vesicular elements present along the apical end provide an endocytic entry. In contrast, those present along the basal end are labeled with sodium [ 35 S]‐sulfate, suggesting that they may be exocytic vesicles containing a sulfo‐conjugated secretory product. In vivo exposure to sodium [ 35 S]‐sulfate caused radioactivity to appear over the Golgi apparatus and some nearby vesicles of the follicle cell cytoplasm, including the exocytic vesicles. The intracellular pathway of the follicle cells was also examined by immunogold labeling using a monoclonal antibody raised against a 85 kDa fat body derived protein. Under these conditions, gold particles were consistently detected over the Golgi apparatus and the vesicular elements lying along both poles of the follicle cell membrane. Based on this evidence, it is concluded that follicular cells in stick insect ovarioles are endowed with the ability to undergo transcytosis by providing an endocytic entry along the apical end and by releasing exocytically a sulfo‐conjugated 85 kDa protein along the baso‐lateral domain of the follicle cell membrane.