MOLECULAR REQUIREMENTS FOR ATTACHMENT OF THE GLYCOSYLPHOSPHATIDYLINOSITOL ANCHOR TO THE HUMAN ALPHA FOLATE RECEPTOR

Citation
A. Tomassetti et al., MOLECULAR REQUIREMENTS FOR ATTACHMENT OF THE GLYCOSYLPHOSPHATIDYLINOSITOL ANCHOR TO THE HUMAN ALPHA FOLATE RECEPTOR, Journal of cellular biochemistry, 72(1), 1999, pp. 111-118
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology,"Cell Biology
ISSN journal
0730-2312
Volume
72
Issue
1
Year of publication
1999
Pages
111 - 118
Database
ISI
SICI code
0730-2312(1999)72:1<111:MRFAOT>2.0.ZU;2-8
Abstract
The alpha isoform of the folate receptor (FR) is a 38-KDa glycosylphos phatidylinositol (GPI) protein which mediates the internalization of f olates. The FR amino acid sequence has features typical of GPI-linked proteins, including the presence of a hydrophobic carboxyl-terminus, a hinge region, and a stretch of small and uncharged amino acids. Subst itution of predicted cleavage/attachment Ser(234) With arginine or thr eonine, or replacement of Gly(235) With proline by site-directed mutag enesis had no effect on GPI processing. In fact, CHO cells transfected with each of the three cDNA variants or with FR wild-type showed comp arable amounts of phosphatidylinositol-specific phospholipase C-resist ant FR in double-determinant radioimmunoassay. Western blot analysis o f total cell lysates from all transfectants consistently revealed the 38-KDa FR band. Deletion of residues 233-237 in the amino-terminal por tion of the FR cDNA constructs derived by a polymerase chain reaction strategy abrogated GPI processing, with only a small proportion of the FR remaining in the cytoplasm in four of the five clones tested. This finding suggests that FR residues 233-237 are essential in properly j uxtaposing the FR hydrophobic domain. Together, these data support the hypothesis that the postulated Ser(234) is not the only potential cle avage/attachment site of the alpha isoform of FR. J. Cell. Biochem. 72 :111-118, 1999. (C) 1999 Wiley-Liss, Inc.