Endocytosis of GPI-anchored proteins in human lymphocytes: role of glycolipid-based domains, actin cytoskeleton, and protein kinases.
GPI-anchored surface proteins mediate many important functions, including transport, signal transduction, adhesion, and protection against complement. They cluster into glycolipid-based membrane domains and caveolae, plasmalemmal vesicles involved in the transcytosis and endocytosis of these surface proteins. However, in lymphocytes, neither the characteristic flask shaped caveolae nor caveolin, a transmembrane protein typical of caveolae, have been observed. Here, we show that the GPI-anchored CD59 molecule on Jurkat T cells is internalized after cross-linking, a process inhibited by nystatin, a sterol chelating agent. Clustered CD59 molecules mostly accumulate in non-coated invaginations of the lymphocyte membrane before endocytosis, in marked contrast with the pattern of CD3-TCR internalization. Cytochalasin H blocked CD59 internalization in lymphocytes, but neither CD3 internalization nor transferrin uptake. Confocal microscopy analysis of F-actin distribution within lymphocytes showed that CD59 clusters were associated with patches of polymerized actin. Also, we found that internalization of CD59 was prevented by the protein kinase C inhibitor staurosporine and by the protein kinase A activator forskolin. Thus, in lymphocytes, as in other cell types, glycolipid-based domains provide sites of integration of signaling pathways involved in GPI-anchored protein endocytosis. This process, which is regulated by both protein kinase C and A activity, is tightly controlled by the dynamic organization of actin cytoskeleton, and may be critical for polarized contacts of circulating cells.
Deckert
M
M
Institut National de la Sante et de la Recherche Medicale U343, Hôpital de l'Archet, Nice, France.
Ticchioni
M
M
Bernard
A
A
D000199:Actins / Q000378:metabolism*; D000818:Animals; D018957:CD59 Antigens / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D008214:Lymphocytes / Q000276:immunology / Q000378:metabolism*; D009761:Nystatin / Q000494:pharmacology; D015388:Organelles / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000199:Actins; D018957:CD59 Antigens; D017261:Glycosylphosphatidylinositols; D009761:Nystatin; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C