MHC class II expression is controlled mainly at transcriptional level by class II transactivator (CIITA), which is a non-DNA binding coactivator and serves as a master control factor for MHC class II genes expression. Here, we describe the function of a novel splice-isoform of CIITA, DC-expressed caspase inhibitory isoform of CIITA (or DC-CASPIC), and we show that the expression of DCCASPIC in DC is upregulated upon lipopolysaccharides (LPS) induction. DC-CASPIC localizes to mitochondria, and protein-protein interaction study demonstrates that DC-CASPIC interacts with caspases and inhibits its activity in DC. Consistently, DC-CASPIC suppresses caspases-induced degradation of nitric oxide synthase-2 (NOS2) and subsequently promotes the synthesis of nitric oxide (NO). NO is an essential regulatory molecule that modulates the capability of DC in stimulating T cell proliferation/activation in vitro; hence, overexpression of DC-CASPIC in DC enhances this stimulation. Collectively, our findings reveal that DC-CASPIC is a key molecule that regulates caspases activity and NO synthesis in DC.
Alternative Splicing ; Amino Acid Sequence ; Animals ; Base Sequence ; CARD Signaling Adaptor Proteins ; genetics ; metabolism ; Cell Line ; Dendritic Cells ; drug effects ; immunology ; metabolism ; Humans ; In Vitro Techniques ; Lipopolysaccharides ; pharmacology ; Lymphocyte Activation ; Mice ; Mice, Inbred C57BL ; Mitochondria ; metabolism ; Molecular Sequence Data ; Nitric Oxide ; biosynthesis ; Nitric Oxide Synthase Type II ; metabolism ; Nuclear Proteins ; genetics ; metabolism ; Protein Isoforms ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; T-Lymphocytes ; immunology ; metabolism ; Trans-Activators ; genetics ; metabolism ; Up-Regulation ; drug effects