CD46, trophoblast leukocyte common antigen, membrane cofactor protein (MCP), TLX, MIC10

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Function

cofactor for complement factor I proteolytic cleavage of C3b & C4b
may be involved in the fusion of the spermatozoa with the oocyte during fertilization
also acts as a costimulatory factor for T-cells which induces differentiation of CD4+ into T-regulatory 1 cells
in epithelial cells, isoforms B/D/F/H/J/L/3 are phosphorylated by YES1 in response to infection by Neisseria gonorrhoeae; which promotes infectivity
in T-cells, these isoforms may be phosphorylated by Lck
interacts with C3b & C4b
binds to Measles virus H protein, to human herpesvirus 6 GH protein & to human adenovirus B/D PIV/fiber protein, & acts as a receptor for these viruses
binds to Streptococcus pyogenes M protein & to type IV pili from Neisseria, & may act as a receptor for these bacteria

N-glycosylated on Asn-83; Asn-114 & Asn-273 in most tissues, but probably less N-glycosylated in testis
N-glycosylation on Asn-114 & Asn-273 is required for cytoprotective function
N-glycosylation on Asn-114 is required for Measles virus binding
N-glycosylation on Asn-273 is required for Neisseria binding
N-glycosylation is not required for human adenovirus binding
extensively O-glycosylated in the Ser/Thr-rich domain
O- glycosylation is required for Neisseria binding but not for Measles virus or human adenovirus binding
Sushi domains 1 & 2 are required for interaction with human adenovirus B PIV/FIBER protein & with Measles virus H protein
Sushi domains 2 & 3 are required for Herpesvirus 6 binding
Sushi domain 3 is required for Neisseria binding
Sushi domains 3 & 4 are required for interaction with Streptococcus pyogenes M protein & are the most important for interaction with C3b & C4b
contains 4 Sushi (CCP/SCR) domains

named isoforms=16 Additional isoforms seem to exist; A-N

expressed by all cells except erythrocytes

specific defects in the sperm forms of CD46 were found in 3 infertile patients
defects in CD46 are a cause of atypical hemolytic-uremic syndrome
used by human herpesvirus 6 & measles virus as a receptor
internalized upon binding of Measles virus, Herpesvirus 6 or Neisseria gonorrhoeae, which results in an increased susceptibility of infected cells to complement-mediated injury
in cancer cells or cells infected by Neisseria, shedding leads to a soluble peptide