TY - JOUR
T1 - Cyclic 3',5'-AMP relay in Dictyostelium discoideum
T2 - Adaptation is independent of activation of adenylate cyclase
AU - Theibert, A.
AU - Devreotes, P. N.
PY - 1983
Y1 - 1983
N2 - In Dictyostelium discoideum, binding of cAMP to high affinity surface receptors leads to a rapid activation of adenylate cyclase followed by subsequent adaptation within several minutes. The rate of secretion of [3H]cAMP, which reflects the state of activation of the enzyme, was measured. Caffeine noncompetitively inhibited the response to cAMP. Inhibition was rapidly reversible and pretreatment of cells with caffeine for up to 22 min had little effect on the subsequent responsiveness to cAMP. However, cells pretreated with caffeine plus cAMP for ≥ 8 min did not respond when caffeine was removed and the same concentration of cAMP was applied. The following observations indicate that both adaptation and deaptation to cAMP occurred to the same extent and at the same rate whether or not cAMP synthesis was inhibited. First, when cells were pretreated with 10-9-10-6 M cAMP in the presence or absence of caffeine and the stimulus was switched to a saturating dose of cAMP, the response to the increment was the same whether or not the initial response was blocked. Second, cells progressively lost responsiveness to 10-6 M cAMP as pretreatment with 10-6 M cAMP plus caffeine was extended from 0 to 8 min with the same time course as for those pretreated with 10-6 M cAMP alone. Third, cells which were adapted in the presence of caffeine and cAMP deadapted within the same time period as controls when cAMP was removed. These observations demonstrate that while some part of the activation process is inhibited by caffeine the adaptation process is unaffected. Our conclusion is that adaptation does not depend on the activation of adenylate cyclase.
AB - In Dictyostelium discoideum, binding of cAMP to high affinity surface receptors leads to a rapid activation of adenylate cyclase followed by subsequent adaptation within several minutes. The rate of secretion of [3H]cAMP, which reflects the state of activation of the enzyme, was measured. Caffeine noncompetitively inhibited the response to cAMP. Inhibition was rapidly reversible and pretreatment of cells with caffeine for up to 22 min had little effect on the subsequent responsiveness to cAMP. However, cells pretreated with caffeine plus cAMP for ≥ 8 min did not respond when caffeine was removed and the same concentration of cAMP was applied. The following observations indicate that both adaptation and deaptation to cAMP occurred to the same extent and at the same rate whether or not cAMP synthesis was inhibited. First, when cells were pretreated with 10-9-10-6 M cAMP in the presence or absence of caffeine and the stimulus was switched to a saturating dose of cAMP, the response to the increment was the same whether or not the initial response was blocked. Second, cells progressively lost responsiveness to 10-6 M cAMP as pretreatment with 10-6 M cAMP plus caffeine was extended from 0 to 8 min with the same time course as for those pretreated with 10-6 M cAMP alone. Third, cells which were adapted in the presence of caffeine and cAMP deadapted within the same time period as controls when cAMP was removed. These observations demonstrate that while some part of the activation process is inhibited by caffeine the adaptation process is unaffected. Our conclusion is that adaptation does not depend on the activation of adenylate cyclase.
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U2 - 10.1083/jcb.97.1.173
DO - 10.1083/jcb.97.1.173
M3 - Article
C2 - 6306013
AN - SCOPUS:0020519373
SN - 0021-9525
VL - 97
SP - 173
EP - 177
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 1
ER -