cDNA encoding a functional feline liver/bone/kidney-type alkaline phosphatase.
Feline alkaline phosphatase (FeALP) was copurified with the putative 70-kDa feline leukemia virus subgroup-A (FeLV-A) receptor protein from feline T-lymphocyte cells (FeT) by two-dimensional gel electrophoresis. The sequence of the N-terminal 17 amino acids and five other internal tryptic peptides revealed that it is homologous to the liver/bone/kidney (L/B/K)-type alkaline phosphatase of other mammalian species. Corresponding oligonucleotides were synthesized and used for amplification of a 1.2-kb segment of the FeALP gene by polymerase chain reaction, using phage DNA from a FeT cell cDNA library as template. The 1.2-kb FeALP gene fragment generated was then used as a probe to isolate a 2127-bp L/B/K-type FeALP cDNA clone from the same library harboring a large, intact open reading frame. This cDNA possessed an open reading frame encoding a 524-amino-acid protein including a putative signal peptide of 17 amino acids followed by 14-amino-acid residues identical to the N-terminal sequence determined from the purified protein. Sequences closely related to five tryptic peptides from the purified protein were also contained within the cDNA-encoded protein. Homology with the human, bovine, rat and mouse L/B/K-type ALP was found to be 88-90% at both the nucleotide and the amino acid levels. The cDNA was transferred into a eukaryotic expression vector and expressed following transfection into murine and mink lung fibroblast cell lines. High levels of enzymatically active ALP were detected, along with a 70-kDa protein reactive in immunoblot assay using a polyclonal antibody against the original crude FeALP preparation. FeALP was specifically released from intact cells by treatment with phosphoinositol-specific phospholipase-C. By Northern blot analysis, only one species of mRNA was detected using a 32P-labeled cDNA probe. These results indicate that the 2127-bp cDNA encodes a functional feline L/B/K-type ALP expressed on cell surfaces via phosphatidylinositol-glycan linkage. Despite electrophoretic comigration in two dimensions and following deglycosylation in a third dimension, FeALP failed to function as an FeLV receptor since its expression failed to provide for attachment or entry of virus into cells.
Ghosh
A K
AK
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305-5402, USA.
Mullins
J I
JI
D000469:Alkaline Phosphatase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001842:Bone and Bones / Q000201:enzymology; D002415:Cats; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics*; D006801:Humans; D007668:Kidney / Q000201:enzymology; D005256:Leukemia Virus, Feline / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011991:Receptors, Virus / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014018:Tissue Distribution
D017931:DNA Primers; D018076:DNA, Complementary; D011991:Receptors, Virus; D000469:Alkaline Phosphatase