Cyclic AMP-dependent protein kinase type I mediates the inhibitory effects of 3',5'-cyclic adenosine monophosphate on cell replication in human T lymphocytes.
Human T lymphocytes were used as a model system to study the expression and roles of cAMP-dependent protein kinase isozymes (cAKI and cAKII) in cAMP-induced inhibition of cell replication. Human peripheral blood T lymphocytes expressed mRNA for the alpha-subforms (RI alpha and RII alpha) of the regulatory subunits of cAKI and cAKII and for the alpha- and beta-subforms (C alpha and C beta) of the catalytic subunits of cAK. At the protein level, RI alpha represented approximately 75% of the total R subunit activity, whereas RII alpha (phospho and dephospho forms) accounted for the remaining 25%. RII beta was not detected at either the mRNA or the protein level. The RI alpha protein was mainly (greater than 75%) cytosolic, whereas RII alpha was almost exclusively (greater than 90%) particulate associated. Treatment of proliferating T lymphocytes (activated through the CD3 cell surface marker) with 10 different cAMP analogs demonstrated that all inhibited cell replication in a concentration-dependent manner. The potency (as measured by the concentration giving 50% inhibition, IC50) of the cAMP analogs ranged from 30 microM for 8-chlorophenylthio-cAMP to 1100 microM for 8-piperidino-cAMP. A cAMP analog pair directed to activate cAKI (8-aminohexylamino-cAMP and 8-piperidino-cAMP) synergized in the inhibition of T lymphocyte proliferation, whereas a cAKII-directed cAMP analog pair (8-chlorophenylthio-cAMP and N6-benzoyl-cAMP) did not. We conclude that activation of cAKI is sufficient to inhibit T lymphocyte proliferation. The membrane-bound cAKII may mediate cAMP actions not related to cell replication.
Skålhegg
B S
BS
Institute of Immunology and Rheumatology, Rikshospitalet, Oslo, Norway.
Landmark
B F
BF
Døskeland
S O
SO
Hansson
V
V
Lea
T
T
Jahnsen
T
T
D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D002848:Chromatography, DEAE-Cellulose; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D046911:Macromolecular Substances; D008297:Male; D011494:Protein Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D013737:Testis / Q000201:enzymology
D007527:Isoenzymes; D046911:Macromolecular Substances; D012333:RNA, Messenger; D012313:RNA; D000242:Cyclic AMP; D011494:Protein Kinases