The tetraspanin CD53 protects stressed hematopoietic stem cells via promotion of DREAM complex-mediated quiescence

Hematopoietic stem cells (HSCs) cycle in response to inflammatory and other proliferative stressors; however, they must quickly return to quiescence to avoid exhaustion and maintain their functional integrity. The mechanisms that regulate this return to quiescence are not well understood. Here we show that the tetraspanin CD53 is markedly upregulated in HSCs in response to a variety of inflammatory and proliferative stimuli, and loss of CD53 is associated with prolonged cycling and reduced HSC function in the context of inflammatory stress. Mechanistically, CD53 promotes the activity of the DREAM transcriptional repressor complex, which downregulates genes associated with cycling and division. Proximity labeling and confocal fluorescent microscopy studies show that CD53 interacts with DREAM-associated proteins, specifically promoting the interaction between Rbl2/p130 and its phosphatase, PP2A, effectively stabilizing p130 protein availability for DREAM binding. Together, these data identify a novel mechanism by which stressed HSCs resist continued cycling. Overall design: We profiled HSCs (KSL CD48- CD150+) from the bone marrow and spleen of Cd53 KO mice and their WT littermates treated with G-CSF x 7 days or saline control