The androgen receptor (AR) is a ligand-inducible transcription factor that mediates androgen action in target tissues. Upon ligand binding, the AR binds to thousands of genomic loci and activates a cell-type specific gene program. Prostate cancer growth and progression depend on androgen-induced AR signaling. Treatment of advanced prostate cancer through medical or surgical castration leads to initial response and durable remission, but resistance inevitably develops. In castration-resistant prostate cancer (CRPC), AR activity remains critical for tumor growth despite androgen deprivation. Although previous studies have focused on ligand-dependent AR signaling, in this study we explore AR function under the androgen-deprived conditions characteristic of CRPC. Our data demonstrate that AR persistently occupies a distinct set of genomic loci after androgen deprivation in CRPC. These androgen-independent AR occupied regions have constitutively open chromatin structures that lack the canonical androgen response element and are independent of FoxA1, a transcription factor involved in ligand-dependent AR targeting. Many AR binding events occur at proximal promoters, which can act as enhancers to augment transcriptional activities of other promoters through DNA looping. We further show that androgen-independent AR binding directs a gene expression program in CRPC, which is necessary for the growth of CRPC after androgen withdrawal.

The p400 and SRCAP (Snf2-related CBP activator protein) complexes remodel chromatin by catalyzing deposition of histone H2A.Z into nucleosomes. This remodeling activity has been proposed as a basis for regulation of transcription by these complexes. Transcript levels of p21 or Sp1 mRNAs after knockdown of p400 or SRCAP reveals that each regulates transcription of these promoters differently. In this study, we asked whether deposition of H2A.Z within specific nucleosomes by p400 or SRCAP dictates transcriptional activity. Our data indicates that nucleosome density at specific p21 or Sp1 promoter positions is not altered by the loss of either remodeling complex. However, knockdown of SRCAP or p400 reduces deposition of H2A.Z∼50% into all p21 and Sp1 promoter nucleosomes. Thus, H2A.Z deposition is not targeted to specific nucleosomes. These results indicate that the deposition of H2A.Z by the p400 or SRCAP complexes is not sufficient to determine how each regulates transcription. This conclusion is further supported by studies that demonstrate a SRCAPΔATP mutant unable to deposit H2A.Z has similar transcriptional activity as wild-type SRCAP.

Stress or cocaine evokes either a large increase in systemic vascular resistance (SVR) or a smaller increase in SVR accompanied by an increase in cardiac output (designated vascular and mixed responders, respectively) in Sprague-Dawley rats. We hypothesized that the central nucleus of the amygdala (CeA) mediates this variability. Conscious, freely-moving rats, instrumented for measurement of arterial pressure and cardiac output and for drug delivery into the CeA, were given cocaine (5 mg/kg, iv, 4-6 times) and characterized as vascular (n=15) or mixed responders (n=10). Subsequently, we administered cocaine after bilateral microinjections (100 nl) of saline or selective agents in the CeA. Muscimol (80 pmol), a GABA A agonist, or losartan (43.4 pmol), an AT 1 receptor antagonist, attenuated the cocaine-induced increase in SVR in vascular responders, selectively, such that vascular responders were no longer different from mixed responders. The corticotropin releasing factor (CRF) antagonist, α-helical CRF 9-41 (15.7 pmol), abolished the difference between cardiac output and SVR in mixed and vascular responders. We conclude that greater increases in SVR observed in vascular responders are dependent on AT 1 receptor activation and, to a lesser extent on CRF receptors. Therefore, AT 1 and CRF receptors in the CeA contribute to hemodynamic response variability to intravenous cocaine.

The central nucleus of the amygdala (CeA) has been shown to play an important role in sympathetic and behavioral responses to stress. We observed a greater vasoconstrictor response to cocaine in some rats (vascular responders or VR) compared to other rats (mixed responders or MR). We hypothesized that the CeA was responsible for greater increases in systemic vascular resistance (SVR) in response to cocaine and that angiotensin II (Ang) and corticotropin‐releasing factor (CRF) receptors were involved. Rats were instrumented for arterial pressure and cardiac output determination and for drug microinjection into the CeA. Rats were given cocaine (5 mg/kg, iv, twice daily, 4X) to determine their response pattern (VR or MR). Subsequently, rats were pretreated with bilateral microinjections (100 nl) of saline, muscimol (80 pmol), losartan (20 ng), or á‐helical‐CRF9‐41 (60 ng) followed by cocaine. Pretreatment with muscimol or losartan attenuated the increase in systemic vascular resistance (SVR) evoked by cocaine. Pretreatment with CRF antagonist prevented the difference in responsiveness between MR and VR by increasing the increase in SVR in MR. Our data suggests that the greater increases in SVR in vascular responders depend on neuronal transmission in the CeA and that Ang receptors facilitate and CRF receptors inhibit SVR responses to cocaine administration. Supported by USPHS RO1 DA13256 and DA0017371.