Dihydrotestosterone activates CREB signaling in cultured hippocampal neurons

Abstract

Although androgens induce numerous actions in brain, relatively little is known about which cell signaling pathways androgens activate in neurons. Recent work in our laboratory showed that the androgens testosterone and dihydrotestosterone (DHT) activate androgen receptor (AR)-dependent mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling. Since the transcription factor cyclic AMP response element binding protein (CREB) is a downstream effector of MAPK/ERK and androgens activate and CREB in non-neuronal cells, we investigated whether androgens activate CREB signaling in neurons. First, we observed that DHT rapidly activates CREB in cultured hippocampal neurons, as evidenced by CREB phosphorylation. Further, we observed that DHT-induced CREB phosphorylation is AR-dependent, as it occurs in PC12 cells stably transfected with AR but in neither wild-type nor empty vector-transfected cells. Next, we sought to identify the signal transduction pathways upstream of CREB phosphorylation using pharmacological inhibitors. DHT-induced CREB phosphorylation in neurons was found to be dependent upon protein kinase C (PKC) signaling but independent of MAPK/ERK, phosphatidylinositol 3-kinase, protein kinase A, and Ca 2+ /calmodulin-dependent protein kinase IV. These results demonstrate that DHT induces PKC-dependent CREB signaling, which may contribute to androgen-mediated neural functions.

Testosterone modulates spatial recognition memory in male rats

“…Consistent with these findings, there is a greater distribution of androgen receptor mRNA relative to estrogen receptor mRNA in the hippocampus of adult male and female rats (Simerly et al, 1990). In the hippocampus, androgens affect synaptic plasticity (Harley et al, 2000;Pouliot et al, 1996;Sakata et al, 2000;Smith et al, 2002;Ziehn et al, 2012), acetylcholine release (Mitsushima et al, 2009), NMDA receptor binding (Kus et al, 1995;Romeo et al, 2005) phosphorylation of protein kinases (Carrier and Kabbaj, 2012;Hatanaka et al, 2009;Nguyen et al, 2005;Rossbach et al, 2007), the expression of transcription factors (Li et al, 2012;Nguyen et al, 2009), neurogenesis (Benice and Raber, 2010;Okamoto et al, 2012;Spritzer and Galea, 2007), the density of synaptic spines in area CA1 (Leranth et al, 2003), and the morphology of dendrites in area CA3 (Hatanaka et al, 2009). As would be expected, many of these cellular responses are dependent upon androgen receptors (Hatanaka et al, 2009;Nguyen et al, 2005;Okamoto et al, 2012).…”

Testosterone and social isolation influence adult neurogenesis in the dentate gyrus of male rats

“…In vitro studies have shown that androgens can activate both the Mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase/Akt (PI-3k/Akt) pathways, both of which regulate cell survival (Nguyen et al, 2005; Gatson et al, 2006). Downstream of these pathways, DHT has also been shown to activate cyclic AMP response element binding protein (CREB), which is known to regulate a wide range of neurotrophic effects (Nguyen et al, 2009). …”

Signatures of sex: Sex differences in gene expression in the vertebrate brain

“…Since Fos is rapidly transcribed in response to neuronal firing, it is possible that neural activity influences estradiol regulation of gene expression. Hormone receptors may also regulate transcription independent of direct DNA binding by controlling the phosphorylation of cAMP‐binding protein (CREB)—a factor that regulates Fos and other genes in response to neural activity (Boulware et al, ; Fix, Jordan, Cano, & Walker, ; Nguyen, Yao, & Pike, ; Shaywitz & Greenberg, ). In primary hippocampal culture and striatal neurons, ERα localized to the postsynaptic membrane signals through group 1 or 2 metabotropic glutamate receptors (mGluRs) to promote or inhibit CREB phosphorylation, respectively (Figure b) (Boulware et al, ; Grove‐Strawser, Boulware, & Mermelstein, ).…”