Survivin is an oncogenic protein that is highly expressed in breast cancer and has a dual function that is dependent on its subcellular localization. In the cytosol, survivin blocks programmed cell ...death by inactivating caspase proteins; however, in the nucleus it facilitates cell division by regulating chromosomal movement and cytokinesis. In prior work, we showed that survivin is acetylated by CREB-binding protein (CBP), which restricts its localization to the nuclear compartment and thereby inhibits its anti-apoptotic function. Here, we identify histone deacetylase 6 (HDAC6) as responsible for abrogating CBP-mediated survivin acetylation in the estrogen receptor (ER)-positive breast cancer cell line, MCF-7. HDAC6 directly binds survivin, an interaction that is enhanced by CBP. In quiescent breast cancer cells in culture and in malignant tissue sections from ER+ breast tumors, HDAC6 localizes to a perinuclear region of the cell, undergoing transport to the nucleus following CBP activation where it then deacetylates survivin. Genetically modified mouse embryonic fibroblasts that lack mhdac6 localize survivin predominantly to the nuclear compartment, whereas wild-type mouse embryonic fibroblasts localize survivin to distinct cytoplasmic structures. Together, these data imply that HDAC6 deacetylates survivin to regulate its nuclear export, a feature that may provide a novel target for patients with ER+ breast cancer.
Background: Survivin is an oncogenic protein that is acetylated by CBP, which restricts its location to the nuclear compartment and blocks its anti-apoptotic effect.
Results: HDAC6 deacetylates survivin to promote its nuclear exit in estrogen receptor-positive breast cancer cells.
Conclusion: Cross-talk between estrogen, CBP, and HDAC6 regulate the amount of nuclear acetylated survivin.
Significance: Understanding how estrogen regulates survivin nuclear export may influence breast cancer treatment.
Summary
Accumulating evidence suggests that adult hippocampal neurogenesis relies on the controlled and continued proliferation of neural progenitor cells (NPCs). With age, neurogenesis decreases ...through mechanisms that remain unclear but are believed to involve changes in the NPC microenvironment. Here, we provide evidence that NPC proliferation in the adult brain is in part regulated by astrocytes via Wnt signaling and that this cellular cross‐talk is modified in the aging brain, leading to decreased proliferation of NPCs. Furthermore, we show that astrocytes regulate the NPC cell cycle by acting on the expression levels of survivin, a known mitotic regulator. Among cell cycle genes found down‐regulated in aged NPCs, survivin was the only one that restored NPC proliferation in the aged brain. Our results provide a mechanism for the gradual loss of neurogenesis in the brain associated with aging and suggest that targeted modulation of survivin expression directly or through Wnt signaling could be used to stimulate adult neurogenesis.
The multiple functions of the oncofetal protein survivin are dependent on its selective expression patterns within immunochemically distinct subcellular pools. The mechanism by which survivin ...localizes to these compartments, however, is only partly understood. Here we show that nuclear accumulation of survivin is promoted by CREB-binding protein (CBP)-dependent acetylation on lysine 129 (129K, Lys-129). We demonstrate a mechanism by which survivin acetylation at this position results in its homodimerization, while deacetylation promotes the formation of survivin monomers that heterodimerize with CRM1 and facilitate its nuclear export. Using proteomic analysis, we identified the oncogenic transcription factor STAT3 as a binding partner of nuclear survivin. We show that acetylated survivin binds to the N-terminal transcriptional activation domain of the STAT3 dimer and represses STAT3 transactivation of target gene promoters. Using multiplex PCR and DNA sequencing, we identified a single-nucleotide polymorphism (A → G) at Lys-129 that exists as a homozygous mutation in a neuroblastoma cell line and corresponds with a defect in survivin nuclear localization. Our results demonstrate that the dynamic equilibrium between survivin acetylation and deacetylation at amino acid 129 determines its interaction with CRM1, its subsequent subcellular localization, and its ability to inhibit STAT3 transactivation, providing a potential route for therapeutic intervention in STAT3-dependent tumors.
The attachment of biotin to a small molecule provides a powerful tool in biology. Here, we present a systematic approach to identify biotinylated analogues of the Hsp90 inhibitor PU-H71 that are ...capable of permeating cell membranes so as to enable the investigation of Hsp90 complexes in live cells. The identified derivative 2g can isolate Hsp90 through affinity purification and, as we show, represents a unique and useful tool to probe tumor Hsp90 biology in live cells by affinity capture, flow cytometry and confocal microscopy. To our knowledge, 2g is the only reported biotinylated Hsp90 probe to have such combined characteristics.
Transient, multi-protein complexes are important facilitators of cellular functions. This includes the chaperome, an abundant protein family comprising chaperones, co-chaperones, adaptors, and ...folding enzymes-dynamic complexes of which regulate cellular homeostasis together with the protein degradation machinery. Numerous studies have addressed the role of chaperome members in isolation, yet little is known about their relationships regarding how they interact and function together in malignancy. As function is probably highly dependent on endogenous conditions found in native tumours, chaperomes have resisted investigation, mainly due to the limitations of methods needed to disrupt or engineer the cellular environment to facilitate analysis. Such limitations have led to a bottleneck in our understanding of chaperome-related disease biology and in the development of chaperome-targeted cancer treatment. Here we examined the chaperome complexes in a large set of tumour specimens. The methods used maintained the endogenous native state of tumours and we exploited this to investigate the molecular characteristics and composition of the chaperome in cancer, the molecular factors that drive chaperome networks to crosstalk in tumours, the distinguishing factors of the chaperome in tumours sensitive to pharmacologic inhibition, and the characteristics of tumours that may benefit from chaperome therapy. We find that under conditions of stress, such as malignant transformation fuelled by MYC, the chaperome becomes biochemically 'rewired' to form a network of stable, survival-facilitating, high-molecular-weight complexes. The chaperones heat shock protein 90 (HSP90) and heat shock cognate protein 70 (HSC70) are nucleating sites for these physically and functionally integrated complexes. The results indicate that these tightly integrated chaperome units, here termed the epichaperome, can function as a network to enhance cellular survival, irrespective of tissue of origin or genetic background. The epichaperome, present in over half of all cancers tested, has implications for diagnostics and also provides potential vulnerability as a target for drug intervention.
Optimal functioning of neuronal networks is critical to the complex cognitive processes of memory and executive function that deteriorate in Alzheimer's disease (AD). Here we use cellular and animal ...models as well as human biospecimens to show that AD-related stressors mediate global disturbances in dynamic intra- and inter-neuronal networks through pathologic rewiring of the chaperome system into epichaperomes. These structures provide the backbone upon which proteome-wide connectivity, and in turn, protein networks become disturbed and ultimately dysfunctional. We introduce the term protein connectivity-based dysfunction (PCBD) to define this mechanism. Among most sensitive to PCBD are pathways with key roles in synaptic plasticity. We show at cellular and target organ levels that network connectivity and functional imbalances revert to normal levels upon epichaperome inhibition. In conclusion, we provide proof-of-principle to propose AD is a PCBDopathy, a disease of proteome-wide connectivity defects mediated by maladaptive epichaperomes.
Cannabinoid agonists such as D9‐THC can decrease operant responding and body temperature. These effects have been characterized in studies using the inverse agonist/antagonist SR 141716A to evaluate ...the CB1‐receptor mediated actions of cannabinoid agonists in rodents. The present studies in squirrel monkeys were conducted to further examine the effects of cannabinoid agonists on operant responding and colonic temperature by evaluating the effects of the novel ligands AM 411 and AM 4054 alone and after treatment with the neutral CB1‐receptor antagonist AM 4113. In behavioral studies, dose ranges for the rate‐decreasing effects of AM 411 (0.1–1 mg/kg) and AM 4054 (0.0032–0.032 mg/kg) first were established in monkeys (n=4) that responded under a fixed‐ratio 30 (FR30) schedule of milk delivery. The highest doses of both agonists decreased response rate to less than 20% of control values. The rate‐decreasing effects of 1 mg/kg AM 411 were blocked by the antagonist AM 4113 (1 mg/kg). In a separate group of monkeys (n=3), the effects of AM 411 and AM 4054 on colonic temperature were determined at an ambient temperature of 30°C. Doses of the agonists that maximally decreased operant responding also decreased colonic temperature by approximately 1°C. In antagonism studies, AM 4113 (0.32 mg/kg) attenuated the decreases in colonic temperature produced by AM 4054. Together, these results indicate that 1.) AM 4054 is more potent than AM 411 in decreasing response rate and colonic temperature; the effects of each agonist on these measures occur at comparable doses; the effects of AM 411 and AM 4054 appear to be mediated through CB1‐receptor mechanisms
(Supported by PHS grant DA19205 and DA7252).
The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of stannous chloride and stannous chloride dihydrate (E 512) as food ...additives. The Panel considered that adequate exposure and toxicity data were available. Stannous chloride is only permitted as food additives in one food category and no reply on the actual use level of stannous chloride (E 512) as a food additive and on its concentration in food was provided by any interested party. According to the Mintel's Global New Products Database (GNPD), stannous chloride was not labelled on any products in the EU nor in Norway. The regulatory maximum level exposure assessment scenario is based on the maximum permitted levels (MPLs) for stannous chloride (E 512), which is 25 mg Sn/kg. The mean exposure to stannous chloride (E 512) from its use as a food additive was below 1.3 μg Sn/kg body weight (bw) per day for all age groups. The 95th percentile of exposure to stannous chloride (E 512) ranged from 0.0 μg Sn/kg bw per day in all groups to 11.2 μg Sn/kg bw per day in adults. Absorption of stannous chloride from the gastrointestinal tract is low there is no concern with respect to carcinogenicity and genotoxicity. Gastrointestinal irritation was reported in humans after ingestion of a bolus dose of 40 mg Sn. The Panel concluded that stannous chloride (E 512) is of no safety concern in this current authorised use and use levels.
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