Regulation of the expression of prostate apoptosis response protein 4 (Par-4) in rat granulosa cells

• Published in: Apoptosis (London) Vol. 12; no. 4; pp. 769 - 779
• Main Authors: Gonzalez, Inmaculada Hernandez, Santana, Pino, Gonzalez-Robayna, Ignacio, Ferrer, Milagros, Morales, Victoria, Blanco, Felix Lopez, Fanjul, Luisa F
• Format: Journal Article
• Language: English
• Published: Netherlands New York : Kluwer Academic Publishers-Plenum Publishers 01.04.2007; Springer Nature B.V
• Subjects: Animals; Apoptosis; Apoptosis - physiology; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Female; Follicle Stimulating Hormone - metabolism; follicular atresia; Gonadotropins, Equine - metabolism; Granulosa; Granulosa Cells - cytology; Granulosa Cells - physiology; Humans; Hybridization; Leucine Zippers; Ovary - cytology; Ovary - growth & development; Ovary - metabolism; Par-4; Pregnancy; Protein Kinase C - metabolism; Rats; Rats, Sprague-Dawley; Regulation; Rodents
• ISSN: 1360-8185; 1573-675X
• DOI: 10.1007/s10495-006-0019-7

The par-4 gene, directs the expression of a protein in the rat ventral prostate after apoptotic stimuli but not growth stimulatory, growth arresting or necrotic signals. Since Par-4 expression appears to be ubiquitous we investigated the possibility of Par-4 having a role in the rat ovary granulosa cells apoptotic death. Par-4 mRNA was detected by RT-PCR with oligonucleotides designed to prime Par-4 leucine zipper in the ovaries of 12 day old rats and reached the higher levels in 24 days old rats. In situ hybridization analysis revealed that Par-4 expression is restricted to granulosa cells. PMSG priming of 24 day old rats for 2 days greatly reduced Par-4 expression in granulosa cells as determined by in situ hybridization, RT-PCR of mRNA and protein immunodetection with Western blot. Granulosa cells placed in serum-fee culture, exhibited increased levels of Par-4 mRNA and protein, in good correlation with the degree of apoptosis. The culture-induced increases in Par-4 are significantly prevented by FSH. Transient transfection of granulosa cells with Par-4 leucine zipper domain that functions as a dominant-negative regulator of Par-4 activity resulted in lower rates of apoptosis while overexpression of the full length Par-4 counteracted FSH effects on apoptosis. Par-4 association with PKCζ which is supposed to inhibit this kinase mediated antiapoptotic way is also prevented by FSH and, FSH antiapoptotic effects are counteracted by a PKCζ specific inhibitor. These findings indicate that FSH by suppressing Par-4 expression in the ovary activates PKCζ-dependent antiapoptotic pathway and suggest that Par-4 is part of the mechanism underlying granulosa cells apoptotic demise.