Selective and programmed cleavage of GPI-anchored proteins from the surface membrane by phospholipase C.
Many surface proteins of eukaryotic cells are tethered to the membrane by a GPI-anchor which is enzymatically cleavable. Here, we investigate cleavage and release of different GPI-proteins by phospholipase C from the outer membrane of the ciliate Paramecium tetraurelia. Our data indicate that different GPI-proteins are not equally cleaved as proteins of the surface antigen family are preferentially released in vitro compared to several smaller GPI-proteins. Likewise, the analysis of culture medium indicates exclusive in vivo release of surface antigens by two phospholipase C isoforms (PLC2 and PLC6). This suggests that phospholipase C shows affinity for select groups of GPI-anchored proteins. Our data also reveal an up-regulation of PLC isoforms in GPI-anchored protein cleavage during antigenic switching. As a consequence, silencing of these PLCs leads to a drastic decrease of antigen concentration in the medium. These results suggest a higher order of GPI-regulation by phospholipase C as cleavage occurs programmed and specific for single GPI-proteins instead of an unspecific shedding of the entire surface membrane GPI-content.
University of Kaiserslautern, Fachbereich Biologie, Gottlieb-Daimler Straße 14, 67663 Kaiserslautern, Germany.
Alexandra
A
Müller
Christine
C
Klöppel
Megan
M
Smith-Valentine
Judith
J
Van Houten
Martin
M
Simon
D000940:Antigenic Variation; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D017077:Culture Media, Conditioned; D004797:Enzyme-Linked Immunosorbent Assay; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D016805:Paramecium tetraurelia / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000954:Antigens, Surface; D017077:Culture Media, Conditioned; D017261:Glycosylphosphatidylinositols; D007527:Isoenzymes; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D010738:Type C Phospholipases