Castor1 overexpression regulates microglia M1/M2 polarization via inhibiting mTOR pathway

Microglia are resident immune cells in the brain and are closely associated with central nervous system inflammation and neurodegenerative diseases. It is known that mammalian target of rapamycin (mTOR) pathway plays an important role in the polarization of microglia. Castor1 has been identified as the cytosolic arginine sensor for the mTOR complex 1 (mTORC1) pathway, but the role of Castor1 in microglial polarization is still unknown. The purpose of this study was to explore the regulatory effect of Castor1 on microglial polarization and the underlying mechanism. The results demonstrated that Castor1 expression was significantly decreased in lipopolysaccharides (LPS) and interferon (IFN)-gamma treated microglia. Castor1 overexpression inhibited the microglia M1 polarization by reducing the expression of M1 related markers. However, the expression of M2-related genes was promoted when Castor1 was overexpressed in IL-4 treated microglia. Mechanistically, Castor1 overexpression inhibited the activation of mTOR signaling pathway. In addition, after treatment with the mTOR activator MHY1485, the inhibitory effect of Castor1 overexpression on M1 polarization was attenuated, indicating that the regulation effects of Castor1 on M1 polarization was dependent on its inhibition of mTOR pathway. We propose that Castor1-mTOR signaling pathway could be considered as a potential target for treatment and intervention of central nervous system-related diseases by regulating microglia polarization.