Introduction: The androgen receptor (AR) is widely expressed in breast cancers and has been proposed as a therapeutic target in estrogen receptor alpha (ER) negative breast cancers that retain AR. However, controversy exists regarding the role of AR, particularly in ER + tumors. Enzalutamide, an AR inhibitor that impairs nuclear localization of AR, was used to elucidate the role of AR in preclinical models of ER positive and negative breast cancer.

Wnt signaling is essential for neuronal development and the maintenance of the developing nervous system. Recent studies indicated that Wnt signaling modulates long term potentiation in adult hippocampal slices. We report here that different Wnt ligands are present in hippocampal neurons of rat embryo and adult rat, including Wnt-4, -5a, -7a, and -11. Wnt-7a acts as a canonical Wnt ligand in rat hippocampal neurons, stimulates clustering of presynaptic proteins, and induces recycling and exocytosis of synaptic vesicles as studied by FM dyes. Wnt-3a has a moderate effect on recycling of synaptic vesicles, and no effect of Wnt-1 and Wnt-5a was detected. Electrophysiological analysis on adult rat hippocampal slices indicates that Wnt-7a, but not Wnt-5a, increases neurotransmitter release in CA3-CA1 synapses by decreasing paired pulse facilitation and increasing the miniature excitatory post-synaptic currents frequency. These results indicate that the presynaptic function of rat hippocampal neurons is modulated by the canonical Wnt signaling.Wnt signaling regulates crucial processes in all multicellular organisms, including cell proliferation, differentiation, migration, and morphogenesis. Since its discovery about 25 years ago, Wnt signaling has been extensively studied for its diverse roles in embryogenesis and cancer (1) and, more recently, in neural development and synaptic plasticity (2-5). Several studies suggest that Wnt factors play a role in the formation of neuronal connections, and other reports indicate a specific effect on synapse assembly; for example, in Drosophila embryos overexpression of the Wnt gene DWnt-3, encoding a protein localized in axonal processes, disrupted the formation of commissural tracts (6). Wnt-3 also regulates terminal arborization of neurotrophin-3-responsive spinal sensory neurons before the formation of sensory motoneuron synapses (7). In developing cerebellum cortex it has been found that conditioned medium from granule cells increases the diameter of mossy fiber axons and growth cone complexity, a result mimicked by 9). Wingless, the prototypical Drosophila Wnt, and its receptor are localized at the larval neuromuscular junction (10). Wingless is secreted by motoneurons and accumulates at both the pre-and postsynaptic terminals. The loss of Wingless leads to reduction in target-dependent synapse formation (10).The expression of Wnt ligands and proteins of the Wnt signaling machinery in the mature nervous system (11, 12) suggests that Wnt signaling plays a role in neuroprotection and synaptic plasticity in addition to its role in neurite patterning in the developing nervous system (3, 5, 13). Indeed, Wnt ligands can act locally to regulate changes in neuronal cell shape and pre-and postsynaptic terminals, which are thought to underlie changes in synaptic function and learning. Thus, Wnt ligands would appear to be particularly well suited as mediators of synaptic plasticity (5,14,15).In the present study we report that Wnt-7a, a canonical ligand that stimulates vesicle clusteri...

During the formation of synapses, specific regions of pre-and postsynaptic cells associate to form a single functional transmission unit. In this process, synaptogenic factors are necessary to modulate pre-and postsynaptic differentiation. In mammals, different Wnt ligands operate through canonical and noncanonical Wnt pathways, and their precise functions to coordinate synapse structure and function in the mature central nervous system are still largely unknown. Here, we studied the effect of different Wnt ligands on postsynaptic organization. We found that Wnt-5a induces short term changes in the clustering of PSD-95, without affecting its total levels. Wnt-5a promotes the recruitment of PSD-95 from a diffuse dendritic cytoplasmic pool to form new PSD-95 clusters in dendritic spines. Moreover, Wnt-5a acting as a non-canonical ligand regulates PSD-95 distribution through a JNK-dependent signaling pathway, as demonstrated by using the TAT-TI-JIP peptide in mature hippocampal neurons. Finally, using adult rat hippocampal slices, we found that Wnt-5a modulates glutamatergic synaptic transmission through a postsynaptic mechanism. Our studies indicate that the Wnt-5a/JNK pathway modulates the postsynaptic region of mammalian synapse directing the clustering and distribution of the physiologically relevant scaffold protein, PSD-95.During the formation of synapses, pre-and postsynaptic sides contain specific molecules that are involved in the regulation and plasticity of synaptic transmission (1-3). Although much is known about the molecular mechanisms of synaptic differentiation, major gaps remain in our understanding of the process, particularly with regard to the signals mediating the structuring of the postsynaptic apparatus of central mammalian synapses (2, 4). At excitatory synapses, the postsynaptic side is characterized by an electrodense thick matrix, called postsynaptic density (PSD).3 The PSD contains key molecules involved in the regulation of glutamate receptor targeting and trafficking (1, 5). There is considerable interest in elucidating the molecular mechanism that controls synaptic targeting and trafficking of these proteins in the postsynaptic region because of their essential role in synaptic plasticity (6). Moreover, in neurodegenerative pathologies, such as Alzheimer disease, it has been evidenced that the postsynaptic region, including several proteins of the PSD, is the primary target of the synaptotoxic effect of the amyloid ␤-peptide (7-9).Wnt signaling is essential for neuronal development and the maintenance of the nervous system (10 -12). Wnt regulates synapse formation; in fact, the pioneering work of Salinas and co-workers (12-15) established that Wnt-7a induces the clustering of presynaptic proteins in young primary cerebellar cultures. Also, Wnt ligands regulate neurogenesis of hippocampal stem cells in the adult rat (16), and Wnt-3a modulates long term potentiation in mouse hippocampal slices (17, 18).The expression of Wnt ligands and proteins of the Wnt signaling machinery in the matu...

Growing evidence indicates that Wingless-type (Wnt) signaling plays an important role in the maturation of the central nervous system. We report here that Wingless-type family member 5A (Wnt-5a) is expressed early in development and stimulates dendrite spine morphogenesis, inducing de novo formation of spines and increasing the size of the preexisting ones in hippocampal neurons. Wnt-5a increased intracellular calcium concentration in dendritic processes and the amplitude of NMDA spontaneous miniature currents. Acute application of Wnt-5a increased the amplitude of field excitatory postsynaptic potentials (fEPSP) in hippocampal slices, an effect that was prevented by calciumchannel blockers. The physiological relevance of our findings is supported by studies showing that Wnt scavengers decreased spine density, miniature excitatory postsynaptic currents, and fEPSP amplitude. We conclude that Wnt-5a stimulates different aspects of synaptic differentiation and plasticity in the mammalian central nervous system.T he Wingless-type (Wnt) signaling pathway modulates several developmental processes, and it is activated by the interaction of the Wnt ligand with members of the Frizzled (Fz) family of seven transmembrane cell-surface receptors (1). It has been reported that Wnt signaling plays a key role in diverse aspects of neuronal development and connectivity (2), regulating axon guidance and remodeling (3), dendrite development (4), synapse formation, (5) and synaptic plasticity (6, 7). Several components of the Wnt pathway are localized at adult synapses, indicating that the molecular machinery required to transduce Wnt signaling is structurally localized at central synapses (8). Different pathways have been described downstream of Fz receptors: the canonical Wnt/β-catenin pathway and the noncanonical ones which involve intracellular signaling by Ca 2+ (the Wnt/Ca 2+ pathway) and the JNK cascade (the Wnt/JNK pathway) (9, 10). Different canonical Wnt ligands have been shown to modulate the presynaptic region. Wnt-7a increases the clustering of synapsin 1 in cerebellar neurons (3) and regulates the trafficking of the α 7 nicotinic acetylcholine receptor to presynaptic terminals in hippocampal neurons (11). In addition, double-mutant mice lacking Wnt-7a and Dishevelled 1 show impaired neurotransmitter release at existing synapses, suggesting a role for Wnt signaling in synaptic transmission (5). Wnt-7a and Wnt-3a were shown to induce the recycling and exocytosis of synaptic vesicles in mature hippocampal neurons and to enhance synaptic transmission in adult hippocampal slices (12). Wnt7a/b levels also were increased in CA3 pyramidal neurons by an enriched environment in which the increase in synapse number at the hippocampal stratum lucidum was shown to be mediated by Wnt signaling (13). Wnt-3a is able to modulate presynaptic differentiation (14,15), and it is released from synapses by an activity-dependent mechanism that facilitates postsynaptic long-term potentiation (6).Recent studies indicated that a different Wnt l...

BackgroundThe Wnt signaling pathway regulates several fundamental developmental processes and recently has been shown to be involved in different aspects of synaptic differentiation and plasticity. Some Wnt signaling components are localized at central synapses, and it is thus possible that this pathway could be activated at the synapse.ResultsWe examined the distribution of the Wnt receptor Frizzled-1 in cultured hippocampal neurons and determined that this receptor is located at synaptic contacts co-localizing with presynaptic proteins. Frizzled-1 was found in functional synapses detected with FM1-43 staining and in synaptic terminals from adult rat brain. Interestingly, overexpression of Frizzled-1 increased the number of clusters of Bassoon, a component of the active zone, while treatment with the extracellular cysteine-rich domain (CRD) of Frizzled-1 decreased Bassoon clustering, suggesting a role for this receptor in presynaptic differentiation. Consistent with this, treatment with the Frizzled-1 ligand Wnt-3a induced presynaptic protein clustering and increased functional presynaptic recycling sites, and these effects were prevented by co-treatment with the CRD of Frizzled-1. Moreover, in synaptically mature neurons Wnt-3a was able to modulate the kinetics of neurotransmitter release.ConclusionOur results indicate that the activation of the Wnt pathway through Frizzled-1 occurs at the presynaptic level, and suggest that the synaptic effects of the Wnt signaling pathway could be modulated by local activation through synaptic Frizzled receptors.

Latrepirdine (Dimebon™) is a pro-neurogenic, antihistaminic compound that has yielded mixed results in clinical trials of mild to moderate Alzheimer’s disease, with a dramatically positive outcome in a Russian clinical trial that was unconfirmed in a replication trial in the United States. We sought to determine whether latrepirdine-stimulated APP catabolism is at least partially attributable to regulation of macroautophagy, a highly conserved protein catabolism pathway that is known to be impaired in brains of patients with Alzheimer’s disease (AD). We utilized several mammalian cellular models to determine whether latrepirdine regulates mTOR- and Atg5-dependent autophagy. Male TgCRND8 mice were chronically administered latrepirdine prior to behavior analysis in the cued and contextual fear conditioning paradigm, as well as immunohistological and biochemical analysis of AD-related neuropathology. Treatment of cultured mammalian cells with latrepirdine led to enhanced mTOR- and Atg5-dependent autophagy. Latrepirdine treatment of TgCRND8 transgenic mice was associated with improved learning behavior and with a reduction in accumulation of Aβ42 and α-synuclein. We conclude that latrepirdine possesses pro-autophagic properties in addition to the previously reported pro-neurogenic properties, both of which are potentially relevant to the treatment and/or prevention of neurodegenerative diseases. We suggest that elucidation of the molecular mechanism(s) underlying latrepirdine effects on neurogenesis, autophagy, and behavior might warranty the further study of latrepirdine as a potentially viable lead compound that might yield more consistent clinical benefit following optimization of its pro-neurogenic, pro-autophagic, and/or pro-cognitive activities.

These results indicate that enzalutamide efficiently inhibits AR signaling, and we suggest that its lack of AR agonist activity may be important for these effects.

Apoptosis plays a major role in controlling both the rate of sperm production and chromosomal abnormalities in adult male testes. However, little is known on the mechanisms controlling induction and execution of apoptosis under physiological conditions. In this work we have uncovered a major role for the cell death receptor Fas in both the extrinsic and intrinsic pathways in normal germ cell apoptosis. We show here that Fas levels increased significantly in a group of germ cell in 25 d old rats, which were identified as spermatocytes and only a few spermatogonia. In addition, we show that isolated spermatocytes expressing high levels of Fas display activation of caspase-8, -9, -3, -6 and -2, as well as increased levels of intracellular calcium and decreased pH, which coincides with stabilization of p53, and transcriptional activation of PUMA and Fas. Therefore, our data strongly suggests that transcriptional up regulation of Fas could predispose a group of spermatocytes to Fas ligand triggering apoptosis by the extrinsic and intrinsic pathway.