CD45 tyrosine phosphatase controls common gamma-chain cytokine-mediated STAT and extracellular signal-related kinase phosphorylation in activated human lymphoblasts: inhibition of proliferation without induction of apoptosis.
The objective of this study was to test whether CD45 signals can influence signaling processes in activated human lymphoblasts. To this end, we generated lymphoblasts which proliferate in response to common gamma-chain cytokines, but readily undergo apoptosis after cytokine withdrawal. In experiments with the CD45R0 mAb UCHL-1, but not control CD45 mAbs, we found significant inhibition of proliferation. Interestingly, the pan-CD45 mAb GAP8.3, which is most effective in inhibition of OKT-3-mediated proliferation in quiescent lymphocytes, was ineffective in lymphoblasts. Addition of CD3 mAb OKT-3 had no influence on IL-2-mediated proliferation (with or without UCHL-1). In contrast, after addition of OKT-3 to IL-4- and IL-7-stimulated proliferation assays, UCHL-1 signals could not significantly alter cellular proliferation. We did not find induction of apoptosis following CD45R0 signaling. In Western blots using mAbs detecting phosphorylated STAT-3, STAT-5, STAT-6, or extracellular signal-related kinase 1/2, we found that CD45R0 signaling could effectively diminish phosphorylation of these intracellular signaling components. Using RT-PCR, we found that CD45R0 signaling inhibited IL-2 mRNA production without major influence on IL-13, IL-5, or IFN-gamma mRNA levels. Costimulation with OKT-3 and IL-2 optimally induced secretion of IFN-gamma, TNF-alpha, and IL-5, which was not decreased by CD45 signals. In conclusion, we illustrate that CD45R0 signals control early cytokine receptor-associated signaling processes and mRNA and DNA synthesis in activated human lymphoblasts. Furthermore, we show the existence of CD45 epitopes (GAP8.3), which are active and critical for signaling in quiescent lymphocytes, but are nonfunctional in activated human lymphoblasts.
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Department of Medicine III, Institute for Clinical Immunology and Rheumatology, University of Erlangen-Nuremberg, Erlangen, Germany.
Kriegel
M
M
Hieronymus
T
T
Geiler
T
T
Winkler
S
S
Kalden
J R
JR
Lorenz
H M
HM
D017209:Apoptosis / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006131:Growth Inhibitors / Q000502:physiology*; D006801:Humans; D053631:Interleukin Receptor Common gamma Subunit; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000502:physiology; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D017493:Leukocyte Common Antigens / Q000502:physiology*; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D008894:Milk Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D020395:Receptors, Interleukin-7 / Q000502:physiology*; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D050800:STAT6 Transcription Factor; D015398:Signal Transduction / Q000276:immunology*; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism
D016207:Cytokines; D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; C507941:IL2RG protein, human; D053631:Interleukin Receptor Common gamma Subunit; D007376:Interleukin-2; D008894:Milk Proteins; D012333:RNA, Messenger; D020395:Receptors, Interleukin-7; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015534:Trans-Activators; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases