sGRP78 enhances selective autophagy of monomeric TLR4 to regulate myeloid cell death.

Soluble glucose regulated protein 78 (sGRP78) has long been suggested as a mediator resolution of inflammation. We previously reported that sGRP78 induced the rapid endocytosis of TLR4 with defective TLR4 signaling. To elucidate the underlying mechanisms, in this study, we investigated how sGRP78 influenced the behavior and trafficking of TLR4 in myeloid cells. It was found that sGRP78 promoted LPS endocytosis with monomeric TLR4. This internalized monomeric TLR4 formed complexes with p62-LC3, and was degraded in autolysosomes. Furthermore, the sGRP78-enhanced autophagy-dependent TLR4 degradation caused apoptosis and ferroptosis in myeloid cells, contributing to the sGRP78-mediated resolution of inflammation. These reports establish innovative mechanisms for endotoxin clearance and immune regulation by TLR4 degradation, linking innate immunity with multiple ancient processes, including autophagy, apoptosis, and ferroptosis, together through a shared resolution-associated molecular pattern (RAMP)-sGRP78.