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Activation of the CAMP signaling pathway increases apoptosis in human B‐precursor cells and is associated with downregulation of Mcl‐1 expression
Author(s) -
Myklebust June Helen,
Josefsen Dag,
Blomhoff Heidi Kiil,
Levy Finn Olav,
Naderi Soheil,
Reed John C.,
Smeland Erlend B.
Publication year - 1999
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199907)180:1<71::aid-jcp8>3.0.co;2-n
Subject(s) - forskolin , apoptosis , downregulation and upregulation , intracellular , protein kinase a , biology , signal transduction , cyclic adenosine monophosphate , microbiology and biotechnology , agonist , endocrinology , medicine , kinase , receptor , biochemistry , stimulation , gene
During B‐ and T‐cell ontogeny, extensive apoptosis occurs at distinct stages of development. Agents that increase intracellular levels of cAMP induce apoptosis in thymocytes and mature B cells, prompting us to investigate the role of cAMP signaling in human CD10 + B‐precursor cells. We show for the first time that forskolin (which increases intracellular levels of cAMP) increases apoptosis in the CD10 + cells in a dose‐dependent manner (19%–94% with 0–1,000 μM forskolin after 48 hours incubation, IC 50 = 150 μM). High levels of apoptosis were also obtained by exposing the cells to the cAMP analogue 8‐chlorophenylthio‐cAMP (8‐CPT‐cAMP). Specific involvement of cAMP‐dependent protein kinase (PKA) was demonstrated by the ability of a cAMP antagonist, Rp‐isomer of 8‐bromo‐adenosine‐ 3′, 5′‐ monophosphorothioate (Rp‐8‐Br‐cAMPS), to reverse the apoptosis increasing effect of the complementary cAMP agonist, Sp‐8‐Br‐cAMPS. Furthermore, we investigated the expression of Bcl‐2 family proteins. We found that treatment of the cells with forskolin or 8‐CPT‐cAMP for 48 hours resulted in a fourfold decline in the expression of Mcl‐1 (n = 6, P = 0.002) compared to control cells. The expression of Bcl‐2, Bcl‐x l , or Bax was largely unaffected. Mature peripheral blood B cells showed a smaller increase in the percentage of apoptotic cells in response to 8‐CPT‐cAMP (1.3‐fold, n = 6, P = 0.045) compared to B‐precursor cells, and a smaller decrease in Mcl‐1 levels (1.5‐fold, n = 4, P = 0.014). Taken together, these findings show that cAMP is important in the regulation of apoptosis in B‐progenitor and mature B cells and suggest that cAMP‐increased apoptosis could be mediated, at least in part, by a decrease in Mcl‐1 levels. J. Cell. Physiol. 180:71–80, 1999. © 1999 Wiley‐Liss, Inc.