scholarly journals Molecular cloning of a murine homologue of membrane cofactor protein (CD46): preferential expression in testicular germ cells

1998 ◽  
Vol 330 (1) ◽  
pp. 163-168 ◽  
Author(s):  
Akira TSUJIMURA ◽  
Kyoko SHIDA ◽  
Masaya KITAMURA ◽  
Midori NOMURA ◽  
Junji TAKEDA ◽  
...  
Keyword(s):  
Germ Cells ◽  
Measles Virus ◽  
Transmembrane Domain ◽  
Chinese Hamster ◽  
Convincing Evidence ◽  
Ovary Cell ◽  
Membrane Cofactor Protein ◽  
Complement Protein ◽  
Germ Cell Differentiation ◽  
Murine Homologue

Human membrane cofactor protein (MCP, CD46) has been suggested, although no convincing evidence has been proposed, to be a fertilization-associated protein, in addition to its primary functions as a complement regulator and a measles virus receptor. We have cloned a cDNA encoding the murine homologue of MCP. This cDNA showed 45% identity in deduced protein sequence and 62% identity in nucleotide sequence with human MCP. Its ectodomains were four short consensus repeats and a serine/threonine-rich domain, and it appeared to be a type 1 membrane protein with a 23-amino acid transmembrane domain and a short cytoplasmic tail. The protein expressed on Chinese hamster ovary cell transfectants was 47 kDa on SDS/PAGE immunoblotting, ~ 6 kDa larger than the murine testis MCP. It served as a cofactor for factor I-mediated inactivation of the complement protein C3b in a homologous system and, to a lesser extent, in a human system. Strikingly, the major message of murine MCP was 1.5 kb and was expressed predominantly in the testis. It was not detected in mice defective in spermatogenesis or with immature germ cells (until 23 days old). Thus, murine MCP may be a sperm-dominant protein the message of which is expressed selectively in spermatids during germ-cell differentiation.

scholarly journals The CD46 transmembrane domain is required for efficient formation of measles-virus-mediated syncytium

1997 ◽  
Vol 322 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Tsukasa SEYA ◽  
Mitsue KURITA ◽  
Kazunori IWATA ◽  
Yusuke YANAGI ◽  
Kazuhiko TANAKA ◽  
...  
Keyword(s):  
Cell Fusion ◽  
Measles Virus ◽  
Deletion Mutant ◽  
Cytopathic Effect ◽  
Transmembrane Domain ◽  
Binding Capacity ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Critical Factor ◽  
Syncytium Formation

Two phosphatidylinositol (PI)-anchored versions of a measles virus (MV) receptor membrane cofactor protein (MCP; CD46) were generated by fusing the extracellular domain of MCP to the decay-accelerating factor (DAF; CD55) or its PI anchor. The PI-anchored forms of MCP expressed on Chinese hamster ovary cells, otherwise non-permissive to MV, conferred a smaller MV cytopathic effect than a wild-type MCP, a Ser/Thr-rich domain-deletion mutant and a cytoplasmic tail-deletion mutant of MCP. Therefore the differences in MV receptor properties between the two PI-anchored and three transmembrane forms were investigated. The PI-anchored forms were predominantly expressed on microvilli as in DAF, whereas the other transmembrane forms were found on intracellular membranes. The PI-anchored forms conferred high MV-binding capacity compared with the transmembrane versions. MV replication was, however, severely suppressed in cells expressing the PI-anchored forms, resulting in ineffective syncytium formation. In contrast, cell-to-cell fusion occurred efficiently after co-transfection of cDNA species encoding MV-H, MV-F and any version of MCP. Thus the PI-anchored forms, despite showing sufficient MV binding and cell-to-cell fusion competence together with MV-H and MV-F, mediate inefficient MV entry or replication, which causes severe suppression of the MV cytopathic effect. A biased receptor distribution on microvilli might participate in the selection of a low MV uptake pathway in the PI-anchored forms of MCP. Taken together, the transmembrane portion of MCP is a critical factor for effective virusŐcell fusion and the subsequent MV replication.

scholarly journals Modulation of complement regulatory function and measles virus receptor function by the serine-threonine-rich domains of membrane cofactor protein (CD46)

1994 ◽  
Vol 304 (1) ◽  
pp. 169-175 ◽  
Author(s):  
K Iwata ◽  
T Seya ◽  
S Ueda ◽  
H Ariga ◽  
S Nagasawa
Keyword(s):  
Measles Virus ◽  
Chinese Hamster ◽  
Syncytium Formation ◽  
Cell Lysis ◽  
Amino Acid Sequences ◽  
Regulatory Function ◽  
Classical Pathway ◽  
Membrane Cofactor Protein ◽  
Cho Cell ◽  
Infectious Dose

Three major membrane cofactor protein (MCP) phenotypes with different serine-threonine (ST)-rich regions, namely STc (L-phenotype), STBC (H or U phenotype) and STABC, and the MCP without the ST domain (delta ST) were expressed in Chinese hamster ovary (CHO) cells by transfecting the respective cDNAs. The expressed molecules migrated with a larger molecular mass on SDS/PAGE than those expected from their amino acid sequences. O-Glycanase digestion showed that this was due to O-linked sugar chains. The apparent sugar contents in each ST segment were compatible with their serine and threonine contents in the ST regions. The functional properties of these phenotypes as inhibitors of human complement (C) and receptors of measles virus (MV) were compared. The classical pathway-dependent CHO cell lysis by human C was more effectively suppressed by the expressed delta ST and STC than by the STABC and STBC phenotypes, although the difference was not so prominent. In contrast, alternative C pathway-dependent CHO-cell lysis was most effectively suppressed by the STABC phenotype and was only slightly blocked by the ST-deleted mutant. MV infection occurred with all of the phenotypes, but the infectious dose required to cause the same level of syncytium formation was 100-times higher in large ST (STABC and STBC) than in small ST (STC and delta ST) phenotypes. Thus, the ST domain serves as a functional modulator in MCP: MCP with a large ST domain having high O-linked sugar contents is favourable to the effective suppression of both the alternative C pathway-mediated cytolysis and MV infection, whereas MCP with a small ST domain is favourable to the suppression of the classical C pathway.

Recombinant Human Soluble Thrombomodulin Delivers Bounded Thrombin to Antithrombin III: Thrombomodulin Associates with Free Thrombin and Is Recycled to Activate Protein C

1993 ◽  
Vol 70 (03) ◽  
pp. 418-422 ◽  
Author(s):  
Masaharu Aritomi ◽  
Naoko Watanabe ◽  
Rika Ohishi ◽  
Komakazu Gomi ◽  
Takao Kiyota ◽  
...  
Keyword(s):  
Protein C ◽  
Antithrombin Iii ◽  
Transmembrane Domain ◽  
Chinese Hamster Ovary Cells ◽  
Time Lag ◽  
Chinese Hamster ◽  
Ovary Cells ◽  
Soluble Thrombomodulin ◽  
Simulation Based ◽  
Recombinant Human Soluble Thrombomodulin

SummaryRecombinant human soluble thrombomodulin (rhs-TM), having no transmembrane domain or chondroitin sulfate, was expressed in Chinese hamster ovary cells. Interactions between rhs-TM, thrombin (Th), protein C (PC) and antithrombin III (ATIII) were studied. Equilibrium between rhs-TM and Th had no detectable time lag in clotting inhibition (K d = 26 nM) or PC activation (K d = 22 nM), while ATIII inhibited Th at a bimolecular rate constant = 5,200 M-1s-1 (K d <0.2 nM). A mixture of ATIII, Th and rhs-TM showed that ATIII reacted with Th slower than rhs-TM, whose presence did not affect the reaction between ATIII and Th. In a mixture of rhs-TM, ATIII and PC, the repeated addition of Th caused the repeated activation of PC; which was consistent with the Simulation based on the assumption that rhs-TM is recycled as a Th cofactor. From these results, we concluded that upon inhibition of the rhs-TM-Th complex by ATIII, rhs-TM is released to recombine with free Th and begins to activate PC, while the Th-ATIII complex does not affect rhs-TM-Th equilibrium.

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