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Blood, 1 December 2008, Vol. 112, No. 12, pp. 4411-4419.
Prepublished online as a Blood First Edition Paper on September 16, 2008; DOI 10.1182/blood-2007-03-080697.
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Submitted March 19, 2007
Accepted July 4, 2008
The IL-15 receptor chain cytoplasmic domain is critical for normal IL-15R function but is not required for trans-presentation
Zheng Wu, Hai-Hui Xue, Jerome Bernard, Rong Zeng, Dmitry Issakov, Julie Bollenbacher-Reilley, Igor M. Belyakov, SangKon Oh, Jay A. Berzofsky, and Warren J. Leonard*
Laboratory of Molecular Immunology, NHLBI, NIH, Bethesda, MD, United States
Vaccine Branch, NCI, NIH, Bethesda, MD, United States
Baylor Institute of Immunology Research, Baylor University Medical Center, Dallas, TX, United States
* Corresponding author; email: wjl{at}helix.nih.gov.
IL-15 is critical for NK-cell development and function and for memory CD8+ T-cell homeostasis. The IL-15 receptor consists of IL-15R , IL-2R , and the common cytokine receptor chain ( c). IL-15R is known to "trans-present" IL-15 to an IL-2R / c heterodimeric receptor on responding cells to initiate signaling. To investigate the importance of the IL-15R cytoplasmic domain, we generated a chimeric receptor consisting of the extracellular domain of IL-15R and intracellular domain of IL-2R (IL-15R ext/IL-2R int) and examined its function in 32D cells, in knock-in (KI) mice, and in adoptive-transfer experiments. The chimeric protein exhibited decreased cell surface expression, and KI mice exhibited diminished NK, NKT, and CD8+ T-cell development and defects in T-cell functional responses. However, 32D cells expressing the chimeric receptor had less IL-15-induced proliferation than WT transfectants with similar levels of IL-15R expression, indicating a signaling role for the IL-15R cytoplasmic domain beyond its effect on expression, and demonstrating that the IL-2R and IL-15R cytoplasmic domains are functionally distinct. Interestingly, adoptive-transfer experiments indicated that the chimeric IL-15R ext/IL-2R int receptor still supports trans-presentation. These experiments collectively indicate that IL-15R can act in cis in addition to acting in trans to present IL-15 to responding cells.

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