CONSTITUTIVE SECRETION OF BETA-TRACE PROTEIN BY CULTIVATED PORCINE CHOROID-PLEXUS EPITHELIAL-CELLS - ELUCIDATION OF ITS COMPLETE AMINO-ACIDAND CDNA SEQUENCES
A. Hoffmann et al., CONSTITUTIVE SECRETION OF BETA-TRACE PROTEIN BY CULTIVATED PORCINE CHOROID-PLEXUS EPITHELIAL-CELLS - ELUCIDATION OF ITS COMPLETE AMINO-ACIDAND CDNA SEQUENCES, Journal of cellular physiology, 169(2), 1996, pp. 235-241
Primary porcine choroid plexus epithelial cells cultivated in chemical
ly defined medium maintain their epithelial characteristics and form c
onfluent monolayers. They produce a fluid the composition of which res
embles cerebrospinal fluid. The present study demonstrates constitutiv
e secretion of large amounts of beta-trace protein. This intrathecally
synthesized protein is a prominent polypeptide constituent of natural
cerebrospinal fluid. According to the identity of amino acid sequence
s it has previously been tentatively identified as a prostaglandin-D s
ynthase and as a member of the lipocalin protein family. beta-Trace wa
s purified from cell culture supernatants and was subjected to tryptic
digestion and amino acid sequencing of the resulting peptides. The co
mplete primary structure of the protein was obtained by additional iso
lation of the cDNA from cultured epithelial cells. The porcine 163-ami
no acid polypeptide showed 69% identity with the human beta-trace and
contained two N-glycosylation sites occupied by complex-type oligosacc
harides as is the case for the human protein. The amino acid sequences
around the N-glycosylation sites of mammalian beta-trace proteins (po
rcine, human, murine, and rat) were highly conserved. The nucleotide s
equence was found to be less conserved; the porcine cDNA had a strikin
gly high GC-content (67%). The constitutive secretion of beta-trace pr
otein from the in vitro cultivated porcine choroid plexus epithelial c
ells demonstrates that the cells have retained their major in vivo phy
siological properties: secretion of cerebrospinal fluid proteins. Ther
efore, this in vitro culture system may be used as a versatile tool fo
r studying the regulation of the formation of cerebrospinal fluid. (C)
1996 Wiley-Liss, Inc.