A heteromorphic protein-tyrosine phosphatase, PTP phi, is regulated by CSF-1 in macrophages.
A novel protein-tyrosine phosphatase, PTP phi, was cloned from a murine macrophage cDNA library. As a result of alternative splicing, macrophage PTP phi mRNAs are predicted to encode two membrane-spanning molecules and a cytosolic enzyme with identical catalytic domains. The membrane-spanning forms differ in the juxtamembrane region, while a start codon downstream of this region is utilized in the translation of the putative cytosolic form. Expression of PTP phi mRNA is low and restricted to macrophage cell lines, macrophage-rich tissues, and brain, kidney, and heart. The mRNA in macrophages and heart is approximately 2.8 kilobases (kb). However, a approximately 5.5-kb transcript in brain and kidney indicates a fourth isoform encoding a large extracellular domain. The approximately 5.5-kb PTP phi brain mRNA encodes the mouse homolog of GLEPP1, a recently reported glomerular epithelial protein. The level of expression of the mRNA encoding the cytosolic form was very low, and only the membrane-spanning proteins (43 and 47 kDa) could be detected in macrophages. Following addition of colony stimulating factor-1 to quiescent BAC1.2F5 macrophages, PTP phi mRNA and protein were down-regulated. The restricted expression of the shorter isoforms of PTP phi and their regulation by colony stimulating factor-1 in macrophages suggest that PTP phi may play a role in mononuclear phagocyte survival, proliferation, and/or differentiation.
Pixley
F J
FJ
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Lee
P S
PS
Dominguez
M G
MG
Einstein
D B
DB
Stanley
E R
ER
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014018:Tissue Distribution
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D016173:Macrophage Colony-Stimulating Factor; D017027:Protein Tyrosine Phosphatases