GPI-microdomains (membrane rafts) and signaling of the multi-chain interleukin-2 receptor in human lymphoma/leukemia T cell lines.
Subunits (alpha, beta and gamma) of the interleukin-2 receptor complex (IL-2R) are involved in both proliferative and activation-induced cell death (AICD) signaling of T cells. In addition, the signaling beta and gamma chains are shared by other cytokines (e.g. IL-7, IL-9, IL-15). However, the molecular mechanisms responsible for recruiting/sorting the alpha chains to the signaling chains at the cell surface are not clear. Here we show, in four cell lines of human adult T cell lymphoma/leukemia origin, that the three IL-2R subunits are compartmented together with HLA glycoproteins and CD48 molecules in the plasma membrane, by means of fluorescence resonance energy transfer (FRET), confocal microscopy and immuno-biochemical techniques. In addition to the beta and gamma(c) chains constitutively expressed in detergent-resistant membrane fractions (DRMs) of T cells, IL-2Ralpha (CD25) was also found in DRMs, independently of its ligand-occupation. Association of CD25 with rafts was also confirmed by its colocalization with GM-1 ganglioside. Depletion of membrane cholesterol using methyl-beta-cyclodextrin substantially reduced co-clustering of CD25 with CD48 and HLA-DR, as well as the IL-2 stimulated tyrosine-phosphorylation of STATs (signal transducer and activator of transcription). These data indicate a GPI-microdomain (raft)-assisted recruitment of CD25 to the vicinity of the signaling beta and gamma(c) chains. Rafts may promote rapid formation of a high affinity IL-2R complex, even at low levels of IL-2 stimulus, and may also form a platform for the regulation of IL-2 induced signals by GPI-proteins (e.g. CD48). Based on these data, the integrity of these GPI-microdomains seems critical in signal transduction through the IL-2R complex.
Matkó
János
J
Department of Biophysics and Cell Biology, Cell Biophysics Research Group of the Hungarian Academy of Sciences, University of Debrecen, Health Science Center, Debrecen, Hungary. Matko@cerberus.elte.hu
Bodnár
Andrea
A
Vereb
György
G
Bene
László
L
Vámosi
György
G
Szentesi
Gergely
G
Szöllösi
János
J
Gáspár
Rezsõ
R
Horejsi
Václav
V
Waldmann
Thomas A
TA
Damjanovich
Sándor
S
D015703:Antigens, CD / Q000302:isolation & purification; D000071178:CD48 Antigen; D005677:G(M1) Ganglioside / Q000302:isolation & purification; D006023:Glycoproteins / Q000302:isolation & purification; D006680:HLA Antigens / Q000302:isolation & purification; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit; D015458:Leukemia, T-Cell / Q000378:metabolism*; D016399:Lymphoma, T-Cell / Q000378:metabolism*; D021962:Membrane Microdomains; D018123:Receptors, Interleukin / Q000302:isolation & purification; D015375:Receptors, Interleukin-2 / Q000302:isolation & purification*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D000071178:CD48 Antigen; C000604065:CD48 protein, human; D006023:Glycoproteins; D006680:HLA Antigens; C508017:IL2RA protein, human; D053645:Interleukin-2 Receptor alpha Subunit; D018123:Receptors, Interleukin; D015375:Receptors, Interleukin-2; D005677:G(M1) Ganglioside