TY - JOUR
T1 - Cyclic 3'-5'-AMP relay in dictyostelium discoideum
T2 - III. the relationship of cAMP synthesis and secretion during the cAMP signaling response
AU - Dinauer, Mary C.
AU - Mackay, Steven A.
AU - Devreotes, Peter N.
PY - 1980/8/1
Y1 - 1980/8/1
N2 - Refinement of a perfusion technique permitted the simultaneous measurement of cAMP-elicited [3H]cAMP secretion and intracellular [3H]cAMP levels in sensitive D. discoideum amoebae. These data were compared with measurements of the rate of [32P]cAMP synthesis by extracts of amoebae sonicated at different times during the cAMP signaling response. cAMP stimulation of intact cells led to a transient activation of adenylate cyclase, which was blocked if 10-4 M NaNa was added with the stimulus. During responses elicited by 10-6 M cAMP, 10-8 M cAMP, and an increment in cAMP from 10-8 M to 10-7 M, the rate of cAMP secretion was proportional to the intracellular cAMP concentration. Removal of a 10-6 M cAMP stimulus 2 min after the initiation of the response led to a precipitous decline in intracellular cAMP. This decline was more rapid than could be accounted for by secretion alone, suggesting intracellular phosphodiesterase destruction of newly synthesized cAMP. Employing these data and a simple rate equation, estimates of the time-course of the transient activation of adenylate cyclase and the rate constants for cAMP secretion and intracellular phosphodiesterase activity were obtained. The calculated rate of cAMP synthesis rose for ≈1 to 2 min, peaked, and declined to approach prestimulus levels after 3 to 4 min. This time-course agreed qualitatively with direct measurements of the time-course of activation, indicating that the activation of adenylate cyclase is a major element in determining the time-course of the cAMP secretion response.
AB - Refinement of a perfusion technique permitted the simultaneous measurement of cAMP-elicited [3H]cAMP secretion and intracellular [3H]cAMP levels in sensitive D. discoideum amoebae. These data were compared with measurements of the rate of [32P]cAMP synthesis by extracts of amoebae sonicated at different times during the cAMP signaling response. cAMP stimulation of intact cells led to a transient activation of adenylate cyclase, which was blocked if 10-4 M NaNa was added with the stimulus. During responses elicited by 10-6 M cAMP, 10-8 M cAMP, and an increment in cAMP from 10-8 M to 10-7 M, the rate of cAMP secretion was proportional to the intracellular cAMP concentration. Removal of a 10-6 M cAMP stimulus 2 min after the initiation of the response led to a precipitous decline in intracellular cAMP. This decline was more rapid than could be accounted for by secretion alone, suggesting intracellular phosphodiesterase destruction of newly synthesized cAMP. Employing these data and a simple rate equation, estimates of the time-course of the transient activation of adenylate cyclase and the rate constants for cAMP secretion and intracellular phosphodiesterase activity were obtained. The calculated rate of cAMP synthesis rose for ≈1 to 2 min, peaked, and declined to approach prestimulus levels after 3 to 4 min. This time-course agreed qualitatively with direct measurements of the time-course of activation, indicating that the activation of adenylate cyclase is a major element in determining the time-course of the cAMP secretion response.
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U2 - 10.1083/jcb.86.2.537
DO - 10.1083/jcb.86.2.537
M3 - Article
C2 - 6249825
AN - SCOPUS:0018948089
SN - 0021-9525
VL - 86
SP - 537
EP - 544
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 2
ER -