and clearance of cells

Macrophages specifically engulf apoptotic cells but not healthy cells. Phosphatidylserine (PtdSer) is localized at the inner leaflet of plasma membranes as a result of the action of flippases (ATP11A and 11C). When cells undergo apoptosis, caspase 3 cleaves and inactivates the flippases, while simultaneously cleaving XKR8 to activate its phospholipid scramblase activity. PtdSer is thus swiftly and irreversibly exposed to the cell surface as an 'eat me' signal. Tissue resident macrophages recognize the apoptotic cells using a PtdSer-receptor TIM4 and engulf them with TAM tyrosine-kinase receptors, and integrins. The PtdSer 'eat me' signal appears to override 'don't eat me' signals in most cases.

Automated summary

During apoptosis, phosphatidylserine (PtdSer) is swiftly exposed on the cell surface, acting as a signal for macrophages to recognize and engulf the apoptotic cells. By utilizing specific receptors and tyrosine kinase receptors, macrophages can effectively recognize and engulf these apoptotic cells.