Expression of a hybrid complement regulatory protein, membrane cofactor protein decay accelerating factor on Chinese hamster ovary. Comparison of its regulatory effect with those of decay accelerating factor and membrane cofactor protein.
C activation on the cell surface is supposedly regulated by membrane cofactor protein (MCP) and decay accelerating factor (DAF). These are complementary in function: MCP acts as a cofactor in factor I-mediated C3b and C4b inactivation, thus preventing the assembly of C3 convertases, whereas DAF accelerates spontaneous decay of the assembled C3 convertase. In this report, a hybrid MCP-DAF was expressed on Chinese hamster ovary cells by transfecting cDNA, and its regulatory activity was compared with those of MCP and DAF transfectants and with a transfectant expressing both MCP and DAF (MCP + DAF). The C3 deposition on sensitized CHO cells through activation of the classical pathway was blocked to a different degree with these transfectants, the order being MCP + DAF > DAF > hybrid MCP-DAF > MCP. Likewise, the C3 deposition via the alternative pathway was blocked efficiently in the order hybrid > MCP + DAF > MCP. The C-mediated cytolysis of CHO cells virtually reflected the degree of C3 fragment deposition. The MCP-DAF transfectant acquired additive protective activity against alternative pathway-mediated C3 deposition and cytolysis but was less potent in circumventing classical pathway attack than cells that expressed DAF alone or DAF + MCP. Hybrid MCP-DAF may be useful for alleviating C-mediated cell damage, especially via the alternative pathway.
Iwata
K
K
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Seya
T
T
Ariga
H
H
Nagasawa
S
S
D000818:Animals; D015703:Antigens, CD / Q000737:chemistry*; D001483:Base Sequence; D018958:CD55 Antigens; D016466:CHO Cells; D003176:Complement C3 / Q000378:metabolism*; D015938:Complement Membrane Attack Complex / Q000037:antagonists & inhibitors*; D003170:Complement Pathway, Alternative; D003171:Complement Pathway, Classical; D006224:Cricetinae; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000494:pharmacology
D015703:Antigens, CD; D018958:CD55 Antigens; D003176:Complement C3; D015938:Complement Membrane Attack Complex; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins