IL-15/IL-15Ralpha intracellular trafficking in human melanoma cells and signal transduction through the IL-15Ralpha.
There are two IL-15 isoforms and eight isoforms for the IL-15Ralpha chain whose biological role is poorly understood. Here, we have analysed the intracellular trafficking of IL-15 and IL-15Ralpha and tried to shed some light on their function(s). In IL-15/GFP CHO transfectants both IL-15 isoforms show nuclear localization. Two melanoma cell lines (MELP and MELREO) spontaneously expressing the IL-15 isoforms, display different intracellular trafficking of the IL-15/IL-15Ralpha complex. In MELP cells only IL-15Ralpha is detected inside the nucleus, whereas IL-15 and IL-15Ralpha assemble at the cell surface and are internalized. Moreover, the transducing molecule TRAF2 co-immunoprecipitates with IL-15Ralpha and may be deflected to TNFRI using anti-IL-15 blocking mAbs and TNF-alpha. By contrast, MELREO cells display IL-15Ralpha and IL-15 nuclear localization but only a partial co-localization of these molecules on the cell surface. In these cells, TRAF2 is strongly associated with IL-15Ralpha and cannot be deflected by any treatment. Since TRAF2 activates the transcription factor NF-kappaB, IL-15 through IL-15Ralpha, could have a role in the control of this pathway. Indeed, anti-IL-15 MaB inhibit the constitutive nuclear localization of NFkappaB and the phosphorylation of its inhibitor Ikappa-Balpha. Thus, IL-15Ralpha controls NF-kappaB activation, however differences in the intracellular trafficking of the IL-15 and/or IL-15Ralpha suggest a different biological role for this complex in MELP versus MELREO cells.
Pereno
R
R
U506 INSERM Hôpital Paul Brousse 94807 Villejuif, France.
Giron-Michel
J
J
Gaggero
A
A
Cazes
E
E
Meazza
R
R
Monetti
M
M
Monaco
E
E
Mishal
Z
Z
Jasmin
C
C
Indiveri
F
F
Ferrini
S
S
Azzarone
B
B
D000818:Animals; D016466:CHO Cells; D002451:Cell Compartmentation; D002467:Cell Nucleus; D006224:Cricetinae; D049452:Green Fluorescent Proteins; D006801:Humans; D019409:Interleukin-15 / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000302:isolation & purification; D008545:Melanoma / Q000378:metabolism*; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism; D011485:Protein Binding; D021382:Protein Sorting Signals; D021122:Protein Subunits; D021381:Protein Transport; D011506:Proteins / Q000302:isolation & purification; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D047992:TNF Receptor-Associated Factor 2
C508024:IL15RA protein, human; D019409:Interleukin-15; D008164:Luminescent Proteins; D016328:NF-kappa B; D021382:Protein Sorting Signals; D021122:Protein Subunits; D011506:Proteins; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D047992:TNF Receptor-Associated Factor 2; D049452:Green Fluorescent Proteins