A new enzyme-linked immunosorbent assay system against the N-terminal propiece of interleukin-1α

Analysis of the effects of importin α1 on the nuclear translocation of IL-1α in HeLa cells

Interleukin-1α (IL-1α), a cytokine released by necrotic cells, causes sterile inflammation. On the other hand, IL-1α is present in the nucleus and also regulates the expression of many proteins. A protein substrate containing a classical nuclear localization signal (cNLS) typically forms a substrate/importin α/β complex, which is subsequently transported to the nucleus. To the best of our knowledge, no study has directly investigated whether IL-1α-which includes cNLS-is imported into the nucleus in an importin α/β-dependent manner. In this study, we noted that all detected importin α subtypes interacted with IL-1α. In HeLa cells, importin α1-mediated nuclear translocation of IL-1α occurred at steady state and was independent of importin β1. Importin α1 not only was engaged in IL-1α nuclear transport but also concurrently functioned as a molecule that regulated IL-1α protein level in the cell. Furthermore, we discussed the underlying mechanism of IL-1α nuclear translocation by importin α1 based on our findings.

Nuclear localization of propiece IL-1α in HeLa cells

PURPOSE

The study aimed to examine the nuclear localization of propiece interleukin (IL)-1α (ppIL-1α) and extracellular release rates of ppIL-1α, pIL-1α, and mIL-1α.

METHODS

The subcellular localization of IL-1α molecules was observed in HeLa cells transfected with green fluorescent protein (GFP)-tagged IL-1α. Extracellular release efficiency was examined using N-terminal HiBiT-tagged IL-1α. The nuclear localization status of ppIL-1α was examined by incubating ppIL-1α transfectants with 0.1% Triton X-100 solution or with complete medium on ice.

RESULTS

The results indicated the diffuse cytoplasmic and nuclear localization for m and p and ppIL-1, respectively. All IL-1α forms were released from the cells even in the steady state, and the release efficiency was 25%, 13%, and 8% for mIL-1α, pIL-1α, and ppIL-1α, respectively. Under oxidative stress condition, GFP-mIL-1α was totally diminished, but weak staining of GFP-pIL-1α and GFP-ppIL-1α was detected; nuclear localization of GFP-ppIL-1α was completely abolished by 0.1% Triton X-100 treatment, however, it remained in the nucleus after culture in complete medium on ice.

CONCLUSION

The results of this study showed that ppIL-1α was localized in the nucleus and released extracellularly even in the steady state. Moreover, its cellular localization is not firm, and it is presumed to be floating in the nucleoplasm.

Acid-electrolyzed functional water-induces Interleukin-1α release from Intracellular Storage Sites in Oral Squamous Cell Carcinoma

The aim of this study was to examine the acid-electrolyzed functional water (FW)-mediated cytokine release in an oral squamous cell carcinoma-derived cell line (OSCC) following treatment with FW. FW is generated by the electrolysis of a sodium chloride solution and accelerate the burn wound healing. To elucidate the underlying mechanisms, the cytokine/chemokine secretion profile of HSC3 cells was examined using a cytokine array. FW treatment significantly induced interleukin (IL)-1α secretion, which was confirmed by enzyme-linked immunosorbent assay. Subsequently, the HSC3 cells were pre-treated with cycloheximide (CHX) for 1 h prior to FW stimulation to determine whether the augmented IL-1α secretion was due to enhanced protein synthesis. CHX pre-treatment did not affect IL-1α secretion suggesting that the secreted IL-1α might have been derived from intracellular storage sites. The amount of IL-1α in the cell lysate of the FW-treated HSC3 cells was significantly lower than that of the non-treated cells. Immunofluorescence staining using a polyclonal antibody against full-length IL-1α revealed a drastic reduction in IL-1α inside the FW- treated cells. IL-1α is synthesized in its precursor form (pIL-1α) and cleaved to produce pro-piece and mature IL-1α (ppIL-1α and mIL-1α) inside the cells. In the present study, only pIL-1α was detected within the HSC3 cells in its resting state. However, FW stimulation resulted in the release of the 33 kDa and two other smaller forms (about 19 kDa) of the protein. These results indicates that FW treatment induces IL-1α secretion, a typical alarmin, from the intracellular storage in OSCC cells.