Periventricular Expression of Megalin in Adult Male Rat Brains and In-vitro SHBG Binding to Cells Through Interaction with a Megalin Receptor
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Authors
Behr, Ian J.
Issue Date
2007-04-27
Type
Language
en_US
Keywords
Sex hormone-binding globulin
Alternative Title
Abstract
Sex Hormone Binding Globulin (SHBG) carries androgens and estrogens throughout the
body to specific target cells. It was previously believed that SHBG transported its cargo outside
of target cells, and the hormones then diffused through the membrane into the target cell.
However, recent studies have suggested SHBG binds to a cell surface receptor, and then SHBG
and its associated hormone are internalized by the cell. This paper studies the in vitro interaction
of fluorescently-labeled SHBG with fetal mouse hippochampal cells and fibroblast cells to
determine how blocking one of SHBG’s known receptors, megalin, affects SHBG.
Immunohistochemistry in adult male rat brain sections was performed to localize megalin using
an antibody raised against itself. This identified megalin in ependymal cells lining the lateral and
third ventricles. In vitro results showed fluorescently labeled SHBG (SHBG-Alexa-555™)
bound to the outside of HT22 mouse hippocampal cells and fibroblast NIH3T3 cells after short
treatment periods; longer treatment times resulted in the appearance of granular fluorescence
inside these cells. Binding of SHBG was decreased when cells were treated with megalin
antibody before the addition of fluorescent SHBG; this suggests megalin bound by antibody was
unable to interact with SHBG as strongly. These studies suggest SHBG binds to brain cells
through the interaction with its cell surface receptor megalin, which subsequently internalizes
SHBG and its associated steroid hormone.
Description
1 broadside : ill.
Citation
Publisher
Kalamazoo College