N-cadherin-mediated cell contact inhibits granulosa cell apoptosis in a progesterone-independent manner.

Abstract

Previous studies have shown that both progesterone and cell contact inhibit granulosa cell (GC) apoptosis in vitro. Since the progesterone concentration associated with aggregated GCs may be higher than that of single GCs, experiments were conducted to differentiate progesterone's action from that of cell contact. For these studies, GCs were isolated from immature rats. Large GCs were collected after Percoll gradient centrifugation and placed in serum-free culture for 24 h. These studies confirmed that the rate of apoptosis was 2-3 times higher for single GCs than for aggregated GCs. This relationship was observed in the presence of aminoglutethimide, where progesterone concentrations were 3 ng/ml or less. A dose-response studied revealed that a minimum of 100 ng/ml progesterone were required to suppress apoptosis of single GCs. In addition, a single cell contact was shown to be sufficient to suppress apoptosis, with a small nonsteroidogenic GC being as effective as a large steroidogenic GC. Taken together, these data support the concept that cell contact blocks apoptosis in a progesterone-independent manner. GC contact is due to the presence of gap and adhesion-type junctions. To assess which, if either, of these junctions is involved in mediating the antiapoptotic action of cell contact, cocultures were set-up between GCs and R2C cells. Contact with R2C cells inhibits GC apoptosis, but does not result in the formation of functional gap junctions. This demonstrates that gap junctions are not essential to maintain GC viability. Adhesion-type junctions result from a homophilic binding of N-cadherin, which is expressed by both GCs and R2C cells. When this binding is inhibited by treatment with either an antibody to N-cadherin or a synthetic N-cadherin peptide, cell aggregation is attenuated. For those cells that form cell contacts in the presence of these N-cadherin-binding inhibitors, the percentage of apoptotic cells is increased compared to that in controls. These observations suggest that homophilic binding of N-cadherin molecules on the surface membranes of adjacent GCs initiates a signal transduction cascade that ultimately inhibits apoptosis.

Downregulation of N-cadherin Expression Inhibits Invasiveness, Arrests Cell Cycle and Induces Cell Apoptosis in Esophageal Squamous Cell Carcinoma

“…Besides, inhibition of apoptosis is regarded as one of the mechanisms by which Ncadherin promotes tumorigenesis (22)(23)(24). Our data also showed that downregulation of N-cadherin expression could apparently induce cell apoptosis in EC9706 cells.…”

Stimulation of Apoptosis in Human Granulosa Cells from in Vitro Fertilization Patients and Its Prevention by Dexamethasone: Involvement of Cell Contact and Bcl-2 Expression

“…These results are in line with the observation that intact adherence junctions expressing N-or E-cadherins are important for granulosa cell viability (34,35,61). These results are in line with the observation that intact adherence junctions expressing N-or E-cadherins are important for granulosa cell viability (34,35,61).…”

“…However, their involvement and their fate during apoptosis are not completely understood. N-cadherin and E-cadherin, the major building blocks of adherence junctions, were also found to be involved in preventing apoptosis of rat granulosa cells (33)(34)(35). N-cadherin and E-cadherin, the major building blocks of adherence junctions, were also found to be involved in preventing apoptosis of rat granulosa cells (33)(34)(35).…”

Development of a long-term serum-free culture system for immature granulosa cells from diethylstilboestrol-treated prepubertal rabbits: influence of androstenedione and fibronectin on FSH-induced cytodifferentiation

“…Treatment of granulosa cells with an antiserum against the integrin β-subunit results in reduced progestin synthesis (Aten et al, 1995). FSH enhances gap junction conductance (Godwin et al, 1993) in vitro, and in the present study it may have increased the expression of these proteins either directly, or via oestradiol or progesterone (Farookhi and Blaschuk, 1991;Peluso et al, 1996). The findings of the present study support the contention that fibronectin contributes to the maintenance of steroidogenesis during granulosa cell differentiation.…”