Mast Cells Express Novel Functional IL-15 Receptor α Isoforms

Abstract

Mast cells previously have been reported to be regulated by IL-15 and to express a distinct IL-15R, termed IL-15RX. To further examine IL-15 binding and signaling in mast cells, we have studied the nature of the IL-15R and some of its biological activities in these cells. In this study, we report the existence of three novel isoforms of the IL-15Rα chain in murine bone marrow-derived mast cells as a result of an alternative exon-splicing mechanism within the IL-15Rα gene. These correspond to new mRNA transcripts lacking exon 4; exons 3 and 4; or exons 3, 4, and 5 (IL-15RαΔ4, IL-15RαΔ3,4, IL-15RαΔ3,4,5). After transient transfection in COS-7 cells, all IL-15Rα isoforms associate with the Golgi apparatus, the endoplasmic reticulum, the perinuclear space, and the cell membrane. Analysis of glycosylation pattern demonstrates the usage of a single N-glycosylation site, while no O-glycosylation is observed. Importantly, IL-15 binds with high affinity to, and promotes the survival of, murine BA/F3 cells stably transfected with the IL-15Rα isoforms. Furthermore, we report that signaling mediated by IL-15 binding to the newly identified IL-15Rα isoforms involves the phosphorylation of STAT3, STAT5, STAT6, Janus kinase 2, and Syk kinase. Taken together, our data indicate that murine mast cells express novel, fully functional IL-15Rα isoforms, which can explain the selective regulatory effects of IL-15 on these cells.

Extracellular ATP Induces Cytokine Expression and Apoptosis through P2X7 Receptor in Murine Mast Cells

“…All primers were purchased from Metabion. cDNA was amplified by standard PCR procedure as described previously (30). To evaluate mRNA expression semiquantitatively, in addition to the PCR product from 35 cycles, 15 l of the PCR product from the 25 cycles and the 30 cycles were run simultaneously.…”

IL-15 induces mast cell migration via a pertussis toxin-sensitive receptor

“…Tagaya and co-workers [32] report that signalling during IL-15-induced mast cell proliferation is associated with phosphorylation of STAT-5 and not STAT-6, while Masuda and co-workers [34] report that signalling during IL-15-induced IL-4 expression in mast cells is associated with phosphorylation of STAT-6 and not STAT-5. Finally, Bulanova and co-workers [39] report that IL-15 induced phosphorylation of both STAT-5 and STAT-6. This implies either that IL-15 can signal using a single receptor via either STAT-5 or STAT-6, or two distinct receptor systems and signalling pathways are involved.…”

“…This implies either that IL-15 can signal using a single receptor via either STAT-5 or STAT-6, or two distinct receptor systems and signalling pathways are involved. Recently, Bulanova and co-workers [39] demonstrated that mBMMC express alternatively spliced transcripts for the IL-15Ra. We did not detect these transcripts in our mBMMC, however the full length transcript for the IL-15Ra and the IL-15Ra transcript variant 2D were present (data not shown).…”

Molecular and Functional Characterization of IL-15 in Rainbow TroutOncorhynchus mykiss:A Potent Inducer of IFN-γ Expression in Spleen Leukocytes

“…The NLS of IFN-␥ is involved in complexing STAT1␣ with nuclear importin ␣ for nuclear translocation of STAT1␣, and is crucial for the biological properties of IFN-␥ (73). It is known that STAT3/5/6 are involved in IL-15 signaling in mammals (74) and thus the NLS in trout IL-15 might function to assist the translocation of the STAT3/5/6 transcription factors. Multiple SVs have been reported in both human and mouse resulting in two isoforms of IL-15 molecules being translated (75).…”