Translational initiation regulated by ATM in dendritic cells development

Abstract

Ataxia telangiectasia mutated (ATM) protein has been implicated in multiple pathways such as DNA repair, cell cycle checkpoint, cell growth, development, and stem cell renewal. In this study, we demonstrate evidence that ATM is involved in granulocyte macrophage colony-stimulating factor (GM-CSF)-induced dendritic cell (DC) development from bone marrow (BM) cells. Inactivation of ATM protein results in decreased BM proliferation, leading to reduced DC development and their activity for T cell activation. Expression of Jak2, STAT5, and mTOR is suppressed in both wild-type and ATM-null BM prior to GM-CSF stimulation. Activation of those proteins is delayed and prolonged hypophosphorylation of 4EBP1 is observed in ATM-null BM when treated with GM-CSF, although Erk and p38 are similarly expressed and activated in both wild-type and ATM-null BM cell types. Akt is also suppressed in wild-type BM, and transduction of constitutively active Akt or STAT5 in ATM-null BM restores DC development. Together, these results illustrate that ATM deficiency causes impaired initiation of protein translation in BM, leading to immature development of DC.

Loss of lipid phosphatase SHIP1 promotes macrophage differentiation through suppression of dendritic cell differentiation

“…Triple staining of CD11c, MHCII and CD86 was also performed to examine the ratio of maturation of BMDCs (Figure 2A). 20 First, we observed increased number of total cells in SHIP1-KO BM culture compared to wild-type BM culture ( Figure 2B) as previously described. 17 However, the effect on proliferation was not significant at the later time points (day 6 and 8).…”

“…27,30 However, BMDCs express intermediate or low expression of MHCII and CD86 before antigen-(through Toll-like receptors) induced maturation, and these cells express higher amounts of the same markers during maturation. 20,29 Because of these heterogeneous phenotypes of BMDCs due to distinct maturation states, analysis using only matured BMDCs might be not sufficient to examine the number and function of BMDCs in in vitro BM culture. 29 In this study, we found that SHIP1 is required for development of BMDCs and identified the prominent function of SHIP1 in differentiation rather than maturation through phenotypic observation and cellular separation between BMDCs and BMMs using flow cytometry.…”

“…Immature DCs and mature DCs are distinguished by the expression pattern of MHCII and CD86 in CD11c positive BM cells. 20 In SHIP1-KO BM cultures, the number of CD11c + /MHCII med immature DCs significantly decreased at day 6. Interestingly, compared to day 6, we found increased CD11c + /MHCII med DCs in both the suspension and adherent population at day 8 of SHIP1-KO BM culture, suggesting delayed differentiation at early stages causes the reduction in the total number of BMDCs at day 8 of SHIP1-KO BMDCs.…”

“…9 Our previous study suggested that ataxia telangiectasia mutated (ATM) plays a role in differentiation of BMDCs through the control of protein expression of Jak2, STAT5, and mTor. 20 Also, we proposed that Akt-mediated signaling pathways are critical for ATM-related regulation for BMDCs development. However, it remains to be investigated which mechanism is involved in SHIP1-mediated regulation during myeloid differentiation from precursors.…”

“…19 Furthermore, BMDCs can be divided into two populations, immature and mature cells depending on the level of MHCII (moderate versus high expression, respectively). 20 Examining the expression of costimulation molecules, such as CD86, can provide additional confirmation of the maturation of BMDCs. Therefore, a clear characterization of BMDCs and BMMs in GM-CSF-induced BM culture will facilitate our understanding of the role of SHIP1 has in myeloid development.…”