PARENT SESSION
SLIDE SESSION 8. SIGNAL TRANSDUCTION
Chairs: Teresa Woodruff, Mary Hunziker-Dunn, Chun-Ying Ku (Trainee)
Univ Ottawa-Morisset 218
2:30 PM-4:30 PM
60
PROGESTERONE PROMOTES ASSOCIATION OF PROTEIN KINASE A WITH PREGNANT RAT MYOMETRIAL PLASMA MEMBRANES.
Ku, Chun-Ying1, Sanborn, Barbara, 1
ABSTRACT- The ability of CPT-cAMP to inhibit agonist-stimulated myometrial phosphatidylinositide (PI) turnover diminishes markedly between d19 and d21 in the pregnant rat (Dodge et al, Molec. Endocrinol.13:1977, 1999). Protein kinase A (PKA) associated with AKAP150, a scaffolding protein in the plasma membrane, also decreases over the same time period. To determine the role of hormones in the association of PKA with myometrial plasma membrane, we prolonged pregnancy by injecting progesterone (P, 10mg/day sc in oil) from d17 and shortened pregnancy by injecting the antiprogestin RU486 (3 mg sc in oil on d15). Purified myometrial plasma membrane from each animal was subjected to SDS-PAGE and analyzed by Western blot. PKA association with plasma membrane from control rats decreased gradually between d16 and d21 (delivery at ~d21.5), with 47 +/- 11%(n=5) remaining at d21 compared to d19 (n=6). P treatment maintained PKA association at d21 (123 +/- 23% (n=5) of d19 levels, delivery >d23). After RU486 injection on d15, plasma membrane PKA association relative to control was 100, 74 and 53% at 6, 12 h and 20 h (mean of duplicates), respectively, resembling d21 levels after 20 h (delivery >24 h). AKAP150 concentrations in plasma membrane and PKA in total tissue homogenates did not exhibit a parallel change. These data indicate that P promotes association of PKA with myometrial plasma membrane in the pregnant rat. The decrease in membrane-bound PKA between d19 and d21 and after RU486 precedes the onset of parturition in both experimental paradigms and may be critical for the decrease in the inhibitory effect of cAMP on agonist-induced PI turnover. The mechanisms by which P exerts this action may be direct or indirect and are being explored. Supported by HD09618.
KEY WORDS: protein kinase A, AKAP, progesterone, myometrium