Porcine (Sus scrofa) cellular FLICE-like inhibitory protein (cFLIP):: Molecular cloning and comparison with the human and murine cFLIP

To reveal the molecular regulation mechanism of selective follicular atresia in porcine ovaries, we isolated the porcine cDNA encoding cellular FLICE-like inhibitory protein (cFLIP), which inhibits death receptor-mediated apoptosis signal transduction. Two alternative splicing isoforms of cFLIP, porcine cellular FLIP-short form (pcFLIPs, 642 bp and 214-aa) and -long form (pcFLIPL, 1446 bp and 482-aa), were identified from a cDNA library prepared from follicular granulosa cells of pig ovaries. pcFLIPs and pcFLIPL indicated high identities with human and murine cFLIP, and both of them contain two tandem specific amino acid regions (death effector domain: DED) in their N-terminal, suggesting that pcFLIPs and pcFLIPL inhibit the death receptor-mediated apoptosis signal by binding to other pro-apoptotic factors mediated by DED. pcFLIPs contains a short C-terminal region, while pcFLIPL has a caspase-like domain in the C-terminal region. The reverse transcription-polymerase chain reaction analysis revealed that both pcFLIPS and pcFLIPL mRNAs were highly expressed in granulosa cells of healthy follicles, suggesting that these cFLIPs play important roles in the regulation mechanism of apoptosis in ovarian follicular granulosa cells. The present data will contribute to understanding of the physiological roles of cFLIPs in the apoptosis regulation in porcine tissues.