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Phosphatidylinositol transfer protein in murine embryonal carcinoma cells during retinoic acid‐induced differentiation
Author(s) -
Wit I. Suzanna C.,
Laat Siegfried W.,
Snoek Gerry T.,
Wirtz Karel W. A.
Publication year - 1995
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1046/j.1440-169x.1995.00012.x
Subject(s) - retinoic acid , phosphatidylinositol , microbiology and biotechnology , embryonal carcinoma , chemistry , carcinoma , cellular differentiation , biology , biochemistry , signal transduction , genetics , gene
Phosphatidylinositol transfer protein (PI‐TP) was studied in P19 embryonal carcinoma (EC) cells at different stages of retinoic acid (RA) induced differentiation. Western blot analysis indicated an increased expression of PI‐TP (35 kDa) during differentiation. Western blots of isoelectric focusing gels showed that the 35 kDa band consisted of the PI‐carrying form of PI‐TP (pl 5.5) and of a novel, more acidic form of PI‐TP (pl 5.4), levels of both of which increased during differentiation. These increased levels were not reflected in the in vitro PI‐transfer activity of the cytosolic fraction nor in the mRNA levels as analyzed by northern blotting. By using indirect immunofluorescence it was shown that PI‐TP is localized in the cytoplasm and associated with perinuclear Golgi structures and that this distribution is slightly affected during RA‐induced differentiation. Immunoprecipitation of PI‐TP from [ 32 P]P i labeled cells demonstrated that the level of phosphorylation of PI‐TP is high in undifferentiated P19 EC cells and low after 5 days of RA‐induced differentiation. These results strongly suggest that changes in the levels of PI‐TP are intimately connected with changes in the growth characteristics of P19 EC cells during RA‐induced differentiation. It remains to be established to what extent this connection is governed by the recent finding that PI‐TP is an essential cytosolic factor in stimulating phospholipase C activity.