Aggregation of IgE receptors in rat basophilic leukemia 2H3 cells induces tyrosine phosphorylation of the cytosolic protein-tyrosine phosphatase HePTP.
The cDNA encoding the rat equivalent of the human hematopoietic tyrosine phosphatase, also known as leukocyte phosphatase, was isolated from a rat basophilic leukemia mast cell cDNA library. By two-dimensional electrophoresis, the protein expressed in the mast cells was of a size (40 kDa) and pI (6.9) predicted from the deduced amino acid sequence. Thus, although previously shown to be preferentially expressed in T cells and B cells, the phosphatase is also found in mast cells. By immunofluorescence microscopy, rat hematopoietic tyrosine phosphatase localized to discrete, globular compartments within the cytoplasm and was not found either in the nucleus or associated with the cell surface membrane. Aggregation of high affinity IgE receptors in the mast cells induced tyrosine phosphorylation of the phosphatase. The tyrosine phosphorylation was mimicked by stimulation with calcium ionophore A23187 but not by direct activation of protein kinase C. Since phosphorylation of the phosphatase was dramatically reduced when the cells were activated in Ca(2+)-free media, it is dependent on a rise in intracellular Ca2+. These data strongly suggest that hematopoietic tyrosine phosphatase may be involved in the IgE receptor-mediated signaling cascade.
Swieter
M
M
Laboratory of Immunology, NIDR, National Institutes of Health, Bethesda, Maryland 20892, USA.
Berenstein
E H
EH
Swaim
W D
WD
Siraganian
R P
RP
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000201:enzymology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology; D017931:DNA Primers; D015870:Gene Expression; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D015471:Leukemia, Basophilic, Acute; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010766:Phosphorylation; D019000:Phosphotyrosine; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000378:metabolism*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017455:Receptors, IgE / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D017455:Receptors, IgE; D019000:Phosphotyrosine; D000001:Calcimycin; D014443:Tyrosine; C509249:PTPN6 protein, human; C502159:PTPN7 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C509248:Ptpn6 protein, mouse; C509250:Ptpn6 protein, rat; C502166:Ptpn7 protein, rat; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium