Characterization of the effects of Crbn during efferocytosis

Abstract

The clearance of apoptotic cells by phagocytes, specifically termed as efferocytosis, has indispensable roles in the development, organogenesis, tissue homeostasis and immunological responses. The dysregulation of efferocytosis, like aberrant removal of cellular debris or effusion of dying cell-derived contents into extracellular space, promotes the necrosis, pathological inflammation and autoimmunity diseases. Calcium, as second messenger for transduction of multiple signals, is essential for efficient and continuous efferocytosis. Depletion of calcium in extracellular or intracellular space abolishes the clearance of dying cells by phagocytes. Until now, the significance of calcium influx on phagocytosis has been well studied, however, signaling pathway that allows calcium influx and mechanism by which calcium influx is regulated are not completely understood. Here we reported that depletion of Crbn promotes phagocytic ability by accelerating phagocytic cup closure and calcium influx by Orai1. We found that Orai1, which induces calcium influx, is regulated by Crbn by ubiquitination and proteasomal degradation as substrate of CRL4Crbn E3 ubiquitin ligase. Interestingly, during efferocytosis, the level of Orai1 is enhanced by decreasing interaction with Crbn and ubiquitination, and Orai1 induces calcium influx into phagocytes by binding with Stim1 rather than Crbn and promotes clearance of apoptotic cells. Collectively, our study propose molecular mechanism by which phagocytes operate calcium influx by modulation of Crbn/Orai1 to achieve efficient and continuous efferocytosis.