[XK-related protein 8, processed form]: Phospholipid scramblase that promotes phosphatidylserine exposure on apoptotic cell surface (PubMed:23845944, PubMed:25231987, PubMed:34625749, PubMed:38364890). Phosphatidylserine is a specific marker only present at the surface of apoptotic cells and acts as a specific signal for engulfment (PubMed:23845944, PubMed:34625749, PubMed:38364890). Required for the clearance of apoptotic cells, such as engulfment of apoptotic germ cells by Sertoli cells, clearance of senescent neutrophils or regulation of bipolar cell numbers in the retina (By similarity). In the hippocampus, phosphatidylserine exposure also acts as a specific 'eat-me' marker for axon pruning during brain development (By similarity). Has no effect on calcium-induced exposure of phosphatidylserine (PubMed:23845944). Promotes myoblast differentiation and survival (PubMed:28881496). {ECO:0000250|UniProtKB:Q8C0T0, ECO:0000269|PubMed:23845944, ECO:0000269|PubMed:25231987, ECO:0000269|PubMed:28881496, ECO:0000269|PubMed:34625749, ECO:0000269|PubMed:38364890}. (Microbial infection) Incorporated into Ebola virus-like particles, where its phospholipid scramblase activity is required to promote phosphatidylserine exposure on the surface of viral particles (PubMed:29338048). Externalization of phosphatidylserine on the surface of viral particles is required for uptake by host cells (PubMed:29338048). . This is the function of XKR8 (XK related 8, ENSG00000158156).