Serpin squamous cell carcinoma antigen inhibits UV-induced apoptosis via suppression of c-JUN NH2-terminal kinase

Protection from ultraviolet (UV) irradiation is a fundamental issue for living organisms. Although melanin's critical role in the protection of basal keratinocytes is well understood, other factors remain essentially unknown. We demonstrate that up-regulation of squamous cell carcinoma antigen-1 (SCCA1) suppresses c-Jun NH2-terminal kinase-1 (JNK1) and thus blocks UV-induced keratinocyte apoptosis. We found that serpin SCCA1 is markedly elevated in the top layers of sun-exposed or UV-irradiated epidermis. UV-induced apoptosis was significantly decreased when SCCA was overexpressed in 3T3/J2 cells. It was significantly increased when SCCA was down-regulated with small interfering RNA in HaCaT keratinocytes. A search for SCCA-interacting molecules showed specific binding with phosphorylated JNK. Interestingly, SCCA1 specifically suppressed the kinase activity of JNK1. Upon exposure of keratinocytes to UV, SCCA1 was bound to JNK1 and transferred to the nucleus. Involucrin promoter–driven SCCA1 transgenic mice showed remarkable resistance against UV irradiation. These findings reveal an unexpected serpin function and define a novel UV protection mechanism in human skin

Overexpression of Serpin Squamous Cell Carcinoma Antigens in Psoriatic Skin

Squamous cell carcinoma antigen belongs to the serpin family and is used for the diagnosis and management of squamous cell carcinoma. We investigated the involvement of squamous cell carcinoma antigen in psoriasis, as it is always detected in the sera of patients with psoriasis. Squamous cell carcinoma antigen localization in psoriatic epidermis varied depending on its concentration in the patient's sera. When its level was low in serum, weak and scattered staining was observed in the granular layer. With a high concentration of squamous cell carcinoma antigen, strong staining through the suprabasal to granular layer and condensed staining around the plasma membrane or intracellular space was detected in the affected epidermis. Interestingly, squamous cell carcinoma antigen was abundant in nuclei of the granular layer cells and elongated rete ridges. Immunoelectron microscopy confirmed the localization of squamous cell carcinoma antigen in the nuclei as well as in the periphery of the cell membrane. A cDNA library was constructed from psoriatic epidermis and both clones, SCCA1 and SCCA2, were obtained. Attempts to raise specific antibodies or to prepare cRNA probes for SCCA1 and SCCA2 were unsuccessful because of their nearly identical structures. A primer pair from each reactive site sequence enabled us to give a distinctive product for SCCA1 and SCCA2 by reverse transcription polymerase chain reaction. Analysis using these primers demonstrated that the SCCA2 transcript was specifically expressed in psoriatic skin tissues. Our results suggest that overexpression of squamous cell carcinoma antigens is associated with the disease activity of psoriasis

Critical role of the MCAM-ETV4 axis triggered by extracellular S100A8/A9 in breast cancer aggressiveness

Metastatic breast cancer is the leading cause of cancer-associated death in women. The progression of this fatal disease is associated with inflammatory responses that promote cancer cell growth and dissemination, eventually leading to a reduction of overall survival. However, the mechanism(s) of the inflammation-boosted cancer progression remains unclear. In this study, we found for the first time that an extracellular cytokine, S100A8/A9, accelerates breast cancer growth and metastasis upon binding to a cell surface receptor, melanoma cell adhesion molecule (MCAM). Our molecular analyses revealed an important role of ETS translocation variant 4 (ETV4), which is significantly activated in the region downstream of MCAM upon S100A8/A9 stimulation, in breast cancer progression in vitro as well as in vivo. The MCAM-mediated activation of ETV4 induced a mobile phenotype called epithelial-mesenchymal transition (EMT) in cells, since we found that ETV4 transcriptionally upregulates ZEB1, a strong EMT inducer, at a very high level. In contrast, downregulation of either MCAM or ETV4 repressed EMT, resulting in greatly weakened tumor growth and lung metastasis. Overall, our results revealed that ETV4 is a novel transcription factor regulated by the S100A8/A9-MCAM axis, which leads to EMT through ZEB1 and thereby to metastasis in breast cancer cells. Thus, therapeutic strategies based on our findings might improve patient outcomes

DNAX-activating protein 10 (DAP10) membrane adaptor associates with receptor for advanced glycation end products (RAGE) and modulates the RAGE-triggered signaling pathway in human keratinocytes.

The receptor for advanced glycation end products (RAGE) is involved in the pathogenesis of many inflammatory, degenerative, and hyperproliferative diseases, including cancer. Previously, we revealed mechanisms of downstream signaling from ligand-activated RAGE, which recruits TIRAP/MyD88. Here, we showed that DNAX-activating protein 10 (DAP10), a transmembrane adaptor protein, also binds to RAGE. By artificial oligomerization of RAGE alone or RAGE-DAP10, we found that RAGE-DAP10 heterodimer formation resulted in a marked enhancement of Akt activation, whereas homomultimeric interaction of RAGE led to activation of caspase 8. Normal human epidermal keratinocytes exposed to S100A8/A9, a ligand for RAGE, at a nanomolar concentration mimicked the pro-survival response of RAGE-DAP10 interaction, although at a micromolar concentration, the cells mimicked the pro-apoptotic response of RAGE-RAGE. In transformed epithelial cell lines, A431 and HaCaT, in which endogenous DAP10 was overexpressed, and S100A8/A9, even at a micromolar concentration, led to cell growth and survival due to RAGE-DAP10 interaction. Functional blocking of DAP10 in the cell lines abrogated the Akt phosphorylation from S100A8/A9-activated RAGE, eventually leading to an increase in apoptosis. Finally, S100A8/A9, RAGE, and DAP10 were overexpressed in the psoriatic epidermis. Our findings indicate that the functional interaction between RAGE and DAP10 coordinately regulates S100A8/A9-mediated survival and/or apoptotic response of keratinocytes

TIRAP, an Adaptor Protein for TLR2/4, Transduces a Signal from RAGE Phosphorylated upon Ligand Binding

The receptor for advanced glycation end products (RAGE) is thought to be involved in the pathogenesis of a broad range of inflammatory, degenerative and hyperproliferative diseases. It binds to diverse ligands and activates multiple intracellular signaling pathways. Despite these pivotal functions, molecular events just downstream of ligand-activated RAGE have been surprisingly unknown. Here we show that the cytoplasmic domain of RAGE is phosphorylated at Ser391 by PKCζ upon binding of ligands. TIRAP and MyD88, which are known to be adaptor proteins for Toll-like receptor-2 and -4 (TLR2/4), bound to the phosphorylated RAGE and transduced a signal to downstream molecules. Blocking of the function of TIRAP and MyD88 largely abrogated intracellular signaling from ligand-activated RAGE. Our findings indicate that functional interaction between RAGE and TLRs coordinately regulates inflammation, immune response and other cellular functions