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Endocytosis of GPI-Anchored Proteins in Human Lymphocytes: Role of Glycolipid-Based Domains, Actin Cytoskeleton, and Protein Kinases

Marcel Deckert, Michel Ticchioni and Alain Bernard
The Journal of Cell Biology
Vol. 133, No. 4 (May, 1996), pp. 791-799
Stable URL: http://www.jstor.org/stable/1617498
Page Count: 9
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Endocytosis of GPI-Anchored Proteins in Human Lymphocytes: Role of Glycolipid-Based Domains, Actin Cytoskeleton, and Protein Kinases
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Abstract

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 noncoated 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.

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