Isolation and analysis of a T cell clone variant exhibiting constitutively phosphorylated Ser133 cAMP response element-binding protein.
In driving T cell proliferation, IL-2 stimulates a new program of gene expression that includes proliferating cell nuclear antigen (PCNA), a requisite processivity factor for DNA polymerase delta. PCNA transcription is regulated in part through tandem CRE sequences in the promoter and CRE binding proteins; IL-2 stimulates CREB phosphorylation in the resting cloned T lymphocyte, L2. After culturing L2 cells for greater than 91 days, we consistently isolate a stable variant that exhibits constitutive CREB phosphorylation. L2 and L2 variant cells were tested for IL-2 responsiveness and rapamycin sensitivity with respect to specific kinase activity, PCNA expression and proliferation. In L2 cells, IL-2 stimulated and rapamycin inhibited the following: cAMP-independent CREB kinase activity, PCNA expression and proliferation. In L2 variant cells, CREB kinase activity was constitutively high; IL-2 stimulated and rapamycin blocked PCNA expression and proliferation. These results indicate that IL-2 induces a rapamycin-sensitive, cAMP-independent CREB kinase activity in L2 cells. However, phosphorylation of CREB alone is not sufficient to drive PCNA expression and L2 cell proliferation in the absence of IL-2.
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
S M
SM
Belkowski
C S
CS
Rubin
M B
MB
Prystowsky
D002469:Cell Separation; D016922:Cellular Senescence / Q000276:immunology; D002999:Clone Cells; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004790:Enzyme Induction / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011090:Polyenes / Q000494:pharmacology; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis; D012694:Serine / Q000378:metabolism*; D020123:Sirolimus; D006377:T-Lymphocytes, Helper-Inducer / Q000201:enzymology / Q000378:metabolism*
D017362:Cyclic AMP Response Element-Binding Protein; D007376:Interleukin-2; D011090:Polyenes; D018809:Proliferating Cell Nuclear Antigen; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D020123:Sirolimus