Androgens regulate follicle stage-dependent pro- and anti-apoptosis in teleost ovaries through ZIP9 activation of different G proteins†

Abstract

Androgens mediate a number of processes in mammalian and teleost ovaries in a follicle-stage dependent manner, including follicle growth, survival, and apoptosis. We recently reported that the membrane androgen receptor ZIP9 mediates apoptosis in Atlantic croaker granulosa/theca (G/T) cells from mature ovarian follicles, but the effects of androgens on early stage G/T cells in this model remains unknown. Here we show that testosterone mediates pro- and anti-apoptotic responses in a follicle stage-dependent manner in croaker ovarian follicle cells. Testosterone treatment decreased the incidence of apoptosis in G/T cells from early stage follicles (diameter <300 μm) but increased apoptosis in G/T cells from late stage follicles (diameter >400 μm). Small interfering RNA targeting ZIP9, but not the nuclear androgen receptor, blocked the anti-apoptotic response, indicating ZIP9 mediates anti-apoptotic in addition to pro-apoptotic responses. Testosterone treatment of early stage G/T cells resulted in opposite signaling outcomes from those previously characterized for the ZIP9-mediated apoptotic response including decreased cAMP and intracellular free zinc levels, and downregulation of pro-apoptotic member mRNA expression. While ZIP9-mediated apoptosis involves activation of a stimulatory G protein (Gs), activators of Gs signaling antagonized the anti-apoptotic response. Proximity ligation and G protein activation assays indicated that in G/T cells from early stage follicles ZIP9 is in close proximity and activates an inhibitory G protein, while in G/T cells from late stage follicles ZIP9 is in close proximity and activates Gs. This study demonstrates that ZIP9 mediates opposite survival responses of croaker G/T cells by activating different G proteins in a follicle stage-dependent manner.

The zinc transporter ZIP9 (Slc39a9) regulates zinc dynamics essential to egg activation in zebrafish

“…While this study exhibits the role of ZIP9 in egg zinc dynamics, it is unclear whether the androgen receptor activity of ZIP9 is involved in modulation of zinc. ZIP9 is known to have the capacity to concurrently act as an androgen receptor and zinc transporter in several cell models 1 – 3 , while in other cells the protein’s zinc transporter activity can function in the absence of androgen stimulation 8 – 10 . In the current model, the possibility that androgens play a role in the zinc dynamics mediated by ZIP9 remains to be investigated.…”

“…ZIP9 was first characterized as a mAR in teleost (Atlantic croaker) ovarian tissue and has since been shown to mediate nonclassical androgen actions in a number of fish and mammalian cell models. To date, ZIP9 has been shown to mediate androgeninduced apoptosis and survival of teleost granulosa/theca (G/T) cells 1,3 , an apoptotic response in prostate and breast cancer cells 2,4 , migration of prostate and bladder cancer cells 5,6 , and tight junction formation in murine Sertoli cells 7 . In many of these models, androgen activation of ZIP9 results in elevation of intracellular zinc levels which in turn modulates the downstream physiological response [1][2][3][4] .…”

“…To date, ZIP9 has been shown to mediate androgeninduced apoptosis and survival of teleost granulosa/theca (G/T) cells 1,3 , an apoptotic response in prostate and breast cancer cells 2,4 , migration of prostate and bladder cancer cells 5,6 , and tight junction formation in murine Sertoli cells 7 . In many of these models, androgen activation of ZIP9 results in elevation of intracellular zinc levels which in turn modulates the downstream physiological response [1][2][3][4] . However, ZIP9 also mediates several effects in the absence of androgen stimulation including migration of glioblastoma cells 8 , induction of fibrosis in irradiated skin 9 , and B lymphocyte receptor pathway signaling 10 .…”

“…While both androgens and zinc play vital roles in ovarian physiology, the function of ZIP9 in mediating nonclassical androgen actions and zinc transport within the ovary remains unclear. We recently reported that ZIP9 mediates androgen-induced pro-and anti-apoptotic responses in croaker G/T cells by coupling to different G proteins 3 . These opposite survival responses are follicle-stage dependent in that G/T cells from early-stage follicles exhibit the anti-apoptotic response while G/T cells from later stage follicles (late vitellogenic) exhibit the apoptotic response.…”

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

“…However, testosterone induced apoptosis via activation of Gα s , adenylyl cyclase, protein kinase A, and MAP kinase (Erk1/2) in croaker ovarian cells ( 141 ). Testosterone-induced survival or apoptotic processes in teleost ovarian cells occur via Gα s or Gα i -dependent mechanisms in a ZIP9-dependent and AR-independent manner ( 142 ).…”