Biosynthesis and function of LFA-3 in human mutant cells deficient in phosphatidylinositol-anchored proteins.
Mutants that lack expression of phosphatidylinositol (PI)-anchored proteins were derived from the human B lymphoblastoid JY cell line. It was demonstrated that unlike wild-type cells, which normally express both a transmembrane and a PI-linked form of LFA-3 glycoprotein, the mutant cells expressed only the transmembrane form of LFA-3. [3H]Ethanolamine was not incorporated into LFA-3 of mutant cells, indicating that the anchor moiety was entirely missing. Blockade of normal biosynthesis of the PI-anchored form led to accumulation of two intermediates that may have intact and truncated polypeptide chains. The truncated LFA-3, which was not attached to the cell membrane, was secreted by mutant cells into culture supernatants. A possible division of adhesion function between the two forms of LFA-3 was studied by using the JY cell lines as targets for CTL. Wild-type and mutant JY cells formed conjugates with CTL and were subsequently lysed to a similar extent. In addition, wild-type and mutant JY cells stimulated CTL proliferation to the same extent. Antibody-blocking experiments demonstrated a predominant role for the CD2/LFA-3 pathway in interaction of both wild-type and mutant cells with CTL. Because E exclusively express only the PI-linked LFA-3 form, and this form is known to mediate cell adhesion, the present results indicate that the two distinct membrane-anchored LFA-3 forms are each capable of mediating adhesion. A possible division of signaling functions between the two forms of LFA-3 is under investigation.
Hollander
N
N
Laboratory of Membrane Immunochemistry, Dana Farber Cancer Institute, Boston, MA.
Selvaraj
P
P
Springer
T A
TA
D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000096:biosynthesis* / Q000302:isolation & purification; D018801:CD2 Antigens; D018958:CD55 Antigens; D018968:CD58 Antigens; D002460:Cell Line; D006017:Glycolipids / Q000172:deficiency*; D006026:Glycoside Hydrolases; D017261:Glycosylphosphatidylinositols; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000172:deficiency* / Q000302:isolation & purification; D008565:Membrane Proteins / Q000172:deficiency; D008970:Molecular Weight; D009154:Mutation; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000172:deficiency*; D010727:Phosphoric Diester Hydrolases; D011233:Precipitin Tests; D011498:Protein Precursors / Q000302:isolation & purification; D011971:Receptors, Immunologic; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D018801:CD2 Antigens; D018958:CD55 Antigens; D018968:CD58 Antigens; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010716:Phosphatidylinositols; D011498:Protein Precursors; D011971:Receptors, Immunologic; D010727:Phosphoric Diester Hydrolases; D006026:Glycoside Hydrolases; C020668:glycanase; D043265:Phosphatidylinositol Diacylglycerol-Lyase