MECHANISMS OF HORMONE ACTION
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(592) PROLACTIN STIMULATES CASPASE 9 ISOFORMS IN CULTURED RAT DECIDUAL CELLS.
Ferguson-Gottschall, Susan1, Bowen-Shauver, Jennifer1, Telleria, Carlos1, Mao, Jifang1, Gibori, Geula1, 1 Dept. of Physiology and Biophysics, Chicago, IL
ABSTRACT- Caspase 9 CTD (C-terminal deletion), a recently characterized truncated isoform of caspase 9, is endogenously expressed in multiple tissues and acts as a dominant negative for the full-length protein. By preventing caspase 9 activation of caspase 3, caspase 9 CTD has a protective, anti-apoptotic effect. We have previously shown that prolactin prevents activation of caspase 3 and reduces DNA fragmentation in cultured rat decidual cells. In this study, we set out to determine if prolactin inhibition of apoptosis in the decidua is mediated via caspase 9 CTD. First, we investigated whether caspase 9 is expressed at a time when the decidua is undergoing apoptosis. Using semi-quantitative RT-PCR, we determined that wildtype caspase 9 was highly expressed in apoptotic decidua from day 12 of pseudopregnancy as compared to proliferative tissue from day 8. This suggests a role for caspase 9 in decidual apoptosis. To determine whether prolactin treatment could affect the expression of either wildtype or CTD forms of caspase 9, primary decidual cells from day 9 pseudopregnant rats were treated with a single dose of prolactin (1 g/l). Northern blot analysis revealed that expression of both caspase 9 isoforms increased with time in culture. An additional increase in mRNA expression for both isoforms was observed in response to prolactin treatment, with an increase evident after 15 min and a maximum stimulation at 30 min. The increase in caspase 9 CTD expression (70%) exceeded that of the wildtype (20%). Current experiments are underway to determine whether this disparity leads to changes in the activity of caspase 9 in decidual cells treated with prolactin. Supported by NIH HD12356 and HD11119
KEY WORDS: prolactin, caspase 9, decidua, apoptosis