The effect of circulating serum factors from patients with systemic lupus erythematosus on protein kinase A (PKA) activity and PKA-dependent protein phosphorylation in T lymphocytes.
T lymphocytes from subjects with active systemic lupus erythematosus (SLE) exhibit reduced cAMP-inducible, protein kinase A (PKA)-dependent phosphorylation of several intracellular substrates compared with healthy and disease controls. To ascertain whether the persistent T cell activation observed during active SLE can result in impaired PKA-dependent protein phosphorylation, normal T cells were activated in vitro by monoclonal anti-CD3-epsilon antibody and recombinant IL1-alpha (rIL1-alpha) for 24 hr. T cell activation, verified by IL2 mRNA, IL2 receptor-alpha (IL2R-alpha) mRNA, and IL2R-beta mRNA expression, did not diminish cAMP-inducible, PKA-dependent protein phosphorylation. We also tested the hypothesis that circulating factors present in active SLE serum can decrease cAMP-inducible total PKA phosphotransferase activity and PKA-dependent protein phosphorylation in normal T lymphocytes. T cells cultured for 24 hr in medium supplemented with 10% active SLE sera (from subjects who exhibited the defect of PKA-dependent protein phosphorylation) exhibited similar total PKA phosphotransferase activity and substrate phosphorylation as cells cultured in normal AB serum. Moreover, the addition of interferon-alpha (IFN-alpha) and/or immune complexes (IC) did not diminish either total PKA activity or PKA-dependent substrate phosphorylation. Lastly, we found that the defect of PKA-dependent protein phosphorylation in active SLE T cells could not be reversed by culturing the cells in culture medium supplemented with 10% AB serum for 24 hr. In conclusion, (a) deficient cAMP-inducible, PKA-dependent phosphorylation in SLE T cells is not reversible by culturing cells in vitro; (b) there is no evidence to support the concept that serum factors, including IC and IFN-alpha, can induce a defect of PKA-dependent protein phosphorylation in normal T cells.
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
G M
GM
Kammer
T M
TM
Haqqi
P
P
Hasler
C J
CJ
Malemud
D000328:Adult; D000936:Antigen-Antibody Complex / Q000494:pharmacology; D001483:Base Sequence; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D005260:Female; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008213:Lymphocyte Activation; D008875:Middle Aged; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism* / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
D000936:Antigen-Antibody Complex; D016898:Interferon-alpha; D000242:Cyclic AMP; D011494:Protein Kinases