| Summary: | 碩士 === 國立臺灣大學 === 醫學檢驗暨生物技術學研究所 === 101 === Cullin 4B (Cul4B), one member of cullin family, is a scaffold protein of Cullin4B-RING-E3 ligase complex which ubiquitinate intracellular protein. The targets for cul4B include cell cycle regulation proteins and some DNA replication-related molecules. Patients with defect or mutation of Cul4B have increased frequency and numbers of peripheral monocytes. In addition, RAW264.7 macrophages with knockdown of cul4B expression by shRNA secrete lower level of TNF-α. These results indicated that Cul4B would affect the development and immune function of monocytes/macrophages which are very important for innate immunity. In this study, we generated a myeloid-specific Cul4B deficient mice (LysMCreKI/KI Cul4bf/y or f/f; CKO) to investigate the influence of Cul4B defect on innate immunity. At first, we confirmed that Cul4B gene was deleted in only myeloid cells of CKO mice. We found the number of bone marrow cells and complete blood count and differential count of peripheral blood were no difference in CKO and control mice, suggesting that Cul4B defect on myeloid cells did not affect the development of blood cells. However, after an intraperitoneal injection of LPS, significantly decreased in the body weight and increased immune cells in peritoneal cavity of CKO mice were observed. Surprisingly, each peritoneal exudate cell in LPS injected CKO mice produced fewer proinflammatory cytokines TNF-α and IL-6 than control mice. Furthermore, bone marrow derived macrophages from CKO mice secreted fewer TNF-α and IL-6 upon LPS stimulation but proliferated faster due to the cell cycle acceleration. Given our findings, myeloid-specific Cul4b deficiency worsened LPS induced acute peritonitis. In macrophages, Cul4B deficiency enhanced DNA replication and proliferation but decreased production of proinflammatory cytokines. Our data highlights the new role of Cul4B and maybe other members of cullin family in the immune responses.
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