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Published on: October 2, 2014
HSP90beta is involved in signaling prolactin-induced apoptosis in newt testis
Buget Saribek1, Yuji Jin, Mikiko Saigo
1Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan.
Abstract:
We have shown in vivo and in vitro that prolactin induces apoptosis in the 7th generation of spermatogonia during newt spermatogenesis, but the underlying molecular mechanism remained unknown. To determine the role of heat shock protein (HSP) 90beta, a molecular chaperone for client proteins in signal transduction and transcriptional regulation, in prolactin-induced apoptosis, we cloned HSP90beta cDNA from newt testis. HSP90beta was detected highly at spermatogonial stage and in both the membrane and cytosol fractions only in germ cell-enriched fraction, while prolactin receptor was expressed in the membrane fraction of only germ cells. Co-immunoprecipitation demonstrated that HSP90beta associated constitutively with prolactin receptor on the plasma membrane of germ cells, suggesting that prolactin receptor is also one of the client proteins for HSP90beta. Inhibition of HSP90beta function by geldanamycin was shown to promote spermatogonial apoptosis. Taken together, these results suggest that HSP90beta is involved in signaling prolactin-induced apoptosis through the receptor.
Insights
Heat shock protein 90beta (HSP90beta) mediates prolactin-induced germ cell apoptosis in newts. HSP90beta associates with the prolactin receptor, suggesting a role in signaling this cell death pathway.
Area of Science:
- Reproductive Biology
- Cellular Biology
- Molecular Biology
Background:
- Prolactin induces apoptosis in newt spermatogonia.
- The molecular mechanism of prolactin-induced apoptosis is not fully understood.
Purpose of the Study:
- To investigate the role of heat shock protein 90beta (HSP90beta) in prolactin-induced apoptosis.
- To determine if HSP90beta interacts with the prolactin receptor.
Main Methods:
- Cloning of newt HSP90beta cDNA.
- Detection of HSP90beta and prolactin receptor expression in newt testis.
- Co-immunoprecipitation to assess protein interactions.
- Inhibition of HSP90beta function using geldanamycin.
Main Results:
- HSP90beta is highly expressed in spermatogonia and associates with the prolactin receptor.
- Prolactin receptor is localized to the germ cell membrane.
- Inhibition of HSP90beta function enhances spermatogonial apoptosis.
Conclusions:
- HSP90beta is involved in signaling prolactin-induced apoptosis.
- The prolactin receptor is a client protein of HSP90beta.
- HSP90beta plays a crucial role in regulating germ cell apoptosis during spermatogenesis.
