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Abstract: 405
Alan L. Johnson1 *, Jamie T. Bridgham1
Dept of Biological Sciences, Galvin Lefe Science Center, University of Notre Dame, Notre Dame, Indiana 1
CAR1 is a novel member of the TNF receptor (R) family of proteins which originally was implicated in mediating apoptotic cell death in chick embryo fibroblasts following viral infection. Such cell death occurs in response to receptor interaction with a specific viral envelope protein expressed by the subgroup B (SUB) avian leukosis-sarcoma virus. This receptor, thus far characterized only in avian species, contains two extracellular cysteine-rich domains characteristic of the TNF-R family, a transmembrane domain, and a cytoplasmic death domain (Brojatsch et al., Cell 87: 845, 1996). Northern blot analysis for CAR1 in hen granulosa cells detects a single 2.3 kb transcript which is expressed at higher levels in apoptosis-susceptible prehierarchal follicle (PREH) granulosa compared to apoptosis-resistant preovulatory follicle (PREOv) granulosa (P<0.05); comparatively lower expression is detected in the theca, and levels do not change during follicle development (P>0.05). Significantly, treatment of cultured PREOv granulosa with recombinant SUB, but not a comparable viral coat protein from the related subgroup A virus, induces apoptosis within 6 h, as evidenced by oligonucleosome formation. CAR1 mRNA and protein (by immunoblot analysis) is rapidly up-regulated in both PREH and PREOv granulosa following 3-20 h of culture (by >2.6-fold; P>0.05), while CAR1 mRNA levels are decreased (by 40%) in cultured granulosa cells following treatment for 4 h with the cell death-attenuating cAMP analog, 8-br-cAMP. Taken together, these data provide evidence for CAR1 having a physiological role in mediating granulosa cell apoptosis, and by implication, follicle atresia. (Supported by USDA Grant 95-37203)
This abstract is being presented on Monday, August 2 at 2:00 PM at Todd 125.