Molecular characteristics of porcine Fas-associated death domain (FADD) and procaspase-8.

To reveal the intracellular signal transduction molecules involved in granulosa cell apoptosis in porcine ovarian follicles, we cloned the porcine Fas-associated death domain (FADD), an adaptor protein for the cell death receptor, and procaspase-8, an initiator caspase. Porcine FADD (pFADD) was 636 bp (211 amino acids: aa) long and showed 74.0 and 65.4% homology with human and murine FADD, respectively. Porcine procaspase-8 (pprocaspase-8) was 1,431 bp (476 aa) long and 70.6 and 63.4% homologous with human and murine procaspase-8, respectively. To confirm the apoptosis-inducing abilities, we constructed pFADD and pprocaspase-8 cDNA expression vectors with enhanced green fluorescence protein (EGFP) and then transfected them into human uterine cervix tumor (HeLa-K), human granulosa cell-derived (KGN), murine granulosa-derived tumor (KK1), and porcine granulosa cell-derived (JC410) cells. When pFADD and pprocaspase-8 were overexpressed, cell death was induced in these transfected cells. However when caspase-inhibitor p35 was cotransfected, cell death was inhibited. The pFADD and pprocaspase-8 genes are well conserved, as are the physiological functions of their products.