Localization of human prealbumin in choroid plexus epithelium.

Abstract

Cerebrospinal fluid (CSF) is generally considered to be derived from plasma through a combined process of ultrafiltration and secretion by the choroid plexus. However, the mechanisms ultimately responsible for achieving the final protein composition of CSF are uncertain. Some proteins, in particular prealbumin, are present in quantities not easily explained by usual physicochemical considerations. To investigate the possibility of de novo synthesis by choroid epithelium, we have examined human choroid plexus an ependyma for the presence of prealbumin. Using the peroxidase-antiperoxidase method at the light and electron microscopic level, as well as immunofluorescence, we localized prealbumin in choroid epithelial cytoplasm on the endoplasmic reticulum and in association with the Golgi apparatus. Ependymal cells and stroma did not reveal immunocytochemical labeling. These findings indicate that the choroid plexus epithelium contributes to the final CSF composition by de novo protein synthesis.

Ion Channel Function of Aquaporin-1 Natively Expressed in Choroid Plexus

“…1b,c) with AQP1-specific polyclonal antibodies recognizing the C-terminal domain (Stamer et al, 1995). Coimmunolabeling with antibodies against prealbumin provided a specific marker for choroid plexus cells (Aleshire et al, 1983). Transfection of cultured choroid plexus cells with siRNA against AQP1 dramatically decreased expression of AQP1 protein.…”

.ALPHA.-Fetoprotein Immunoreactivity in Human Choroid Plexus.

“…Similar peptides such as cholecystokinin and gastrin, exist in both brain parenchyma and gut, although they may play different functional roles depending on the organs where they are present, namely as neuromodulators in the brain and as hormones in the gut. In this context a novel concept "brain-liver proteins" may be proposed based upon our finding on AFP in conjunction with previous reports by others on the presence of prealbumin (4,6,13), transferrin (2,6) and ceruloplasmin (3). However, it should be noted that positive immunoreactivity for AFP shown here does not imply synthesis of AFP in the choroid plexus epithelium.…”

Synthesis of Thyroid Hormone Binding Proteins Transthyretin and Albumin by Human Trophoblast

“…TTR is produced predominantly in liver and secreted into plasma. TTR has also been identified in other tissues, including choroid plexus and the retinal pigment epithelium (17), both of which secrete the protein (18). TTR is produced in relatively large amounts in choroid plexus in which it plays an important role in the transport of T 4 from blood into cerebrospinal fluid (19).…”