Molecular and functional analysis of mouse decay accelerating factor (CD55).
Molecular cloning of mouse decay accelerating factor (DAF; CD55) predicted two forms of the molecule, one transmembrane (TM) and the other glycosylphosphatidylinositol (GPI)-anchored; these are encoded by separate genes termed Daf-GPI and Daf-TM. In the present study several additional isoforms of mouse DAF, generated by alternative splicing from these genes, are described. Northern-blot analysis of RNA and reverse transcriptase-PCR from various tissues indicated that spleen and testis expressed high levels of DAF, which comprised several species. These species were cloned and sequence analysis revealed various novel forms in addition to those previously reported. Two novel forms were derived from the Daf-TM gene but the transmembrane sequence defined previously was replaced by a unique GPI-anchor addition sequence; one clone also had part of the serine/threonine/proline (STP) region deleted. A third clone, encoding a transmembrane protein, was also derived from this gene but the entire STP region was deleted. A fourth clone, derived from the Daf-GPI gene, contained a novel C-terminal sequence, suggestive of a secreted form of the protein. Two DAF cDNAs (TM and GPI-anchored) were stably expressed in Chinese hamster ovary cells. When these cells were attacked with mouse or rat complement and analysed for C3b deposition, DAF-transfected cells had greatly reduced C3b deposition compared with controls. Transfection with DAF also conferred protection from complement in a cell-lysis assay, and a soluble, recombinant form of mouse DAF inhibited complement in a haemolytic assay.
Harris
C L
CL
Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
Rushmere
N K
NK
Morgan
B P
BP
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018958:CD55 Antigens / Q000235:genetics* / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D017931:DNA Primers; D051379:Mice; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics; D051381:Rats; D017386:Sequence Homology, Amino Acid
D018958:CD55 Antigens; D017931:DNA Primers; D021382:Protein Sorting Signals