Purification and analysis of the neutral glycan moiety of glycosyl phosphatidylinositol from porcine thyroid cells

Metabolic labelling of inositolphosphate glycan with radioactive precursors is not sufficient to characterize and assess the involvement of the glycos yl phosphatidylinositol/inositolphosphate glycan (GPI/IPG) system in porcin e thyroid cell signal transduction machinery. A protocol is described for t he isolation and purification of free GPI using differential polarity of li pids and sequential thin layer chromatography. The purification until homog eneity of GPI constitutes a required step for gas chromatographic analysis. Next, successive chemical treatments allowed us to remove the neutral glyc an moiety of thyroidal GPI, and its composition was obtained by gas chromat ography. The proposed structure is consistent with data available for GPI a nchor, but differs from compositional analysis data reported for insulin-se nsitive GPI. Our results support the existence in porcine thyroid cells of the GPI IPG system, which can take part in TSH-dependent signal transductio n processes. Copyright (C) 1999 John Wiley & Sons, Ltd.