IL-32[thetas] downregulates CCL5 expression through its interaction with PKC delta and STAT3

• Published in: Cellular signalling 2014-12, Vol.26 (12), p.3007-3015
• Main Authors: Bak, Yesol, Kang, Jeong-Woo, Kim, Man Sub, Park, Yun Sun, Kwon, Taeho, Kim, Soohyun, Hong, Jintae, Yoon, Do-Young
• Format: Article
• Language: English
• Subjects: Assaying; Binding; ELISA; Genes; Interleukin; Modulators; Phosphorylation; Proteins
• ISSN: 0898-6568
• DOI: 10.1016/j.cellsig.2014.09.015

Interleukin-32 (IL-32) exists in several isoforms and plays an important role in inflammatory response. Recently, we identified a new isoform, IL-32[thetas], and performed a microarray analysis to identify IL-32[thetas]-regulated genes in THP-1 myelomonocytic cells. Upon stimulating IL-32[thetas]-expressing THP-1 cells with phorbol myristate acetate (PMA), we found that the CCL5 transcript level was significantly reduced. We confirmed the downregulation of CCL5 protein expression by using an enzyme-linked immunosorbent assay (ELISA). Because STAT3 phosphorylation on Ser727 by PKC delta is reported to suppress CCL5 protein expression, we examined whether IL-32[thetas]-mediated STAT3 Ser727 phosphorylation occurs through an interaction with PKC delta . In this study, we first demonstrate that IL-32[thetas] interacts with PKC delta and STAT3 using co-immunoprecipitation (Co-IP) and pulldown assay. Moreover, STAT3 was rarely phosphorylated on Ser727 in the absence of IL-32[thetas], leading to the binding of STAT3 to the CCL5 promoter. These results indicate that IL-32[thetas], through its interaction with PKC delta , downregulates CCL5 expression by mediating the phosphorylation of STAT3 on Ser727 to render it transcriptionally inactive. Therefore, similar to what we have reported for IL-32 alpha and IL-32 beta , our data from this study suggests that the newly identified IL-32[thetas] isoform also acts as an intracellular modulator of inflammation.