Update and Potential Opportunities in CBP [Cyclic Adenosine Monophosphate (cAMP) Response Element-Binding Protein (CREB)-Binding Protein] Research Using Computational Techniques.

CBP [cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB)-binding protein] is one of the most researched proteins for its therapeutic function. Several studies have identified its vast functions and interactions with other transcription factors to initiate cellular signals of survival. In cancer and other diseases such as Alzheimer's, Rubinstein-taybi syndrome, and inflammatory diseases, CBP has been implicated and hence an attractive target in drug design and development. In this review, we explore the various computational techniques that have been used in CBP research, furthermore we identified computational gaps that could be explored to facilitate the development of highly therapeutic CBP inhibitors.

Simulations suggest pharmacological methods for rescuing long-term potentiation.

Congenital cognitive dysfunctions are frequently due to deficits in molecular pathways that underlie the induction or maintenance of synaptic plasticity. For example, Rubinstein-Taybi syndrome (RTS) is due to a mutation in cbp, encoding the histone acetyltransferase CREB-binding protein (CBP). CBP is a transcriptional co-activator for CREB, and induction of CREB-dependent transcription plays a key role in long-term memory (LTM). In animal models of RTS, mutations of cbp impair LTM and late-phase long-term potentiation (LTP). As a step toward exploring plausible intervention strategies to rescue the deficits in LTP, we extended our previous model of LTP induction to describe histone acetylation and simulated LTP impairment due to cbp mutation. Plausible drug effects were simulated by model parameter changes, and many increased LTP. However no parameter variation consistent with a effect of a known drug class fully restored LTP. Thus we examined paired parameter variations consistent with effects of known drugs. A pair that simulated the effects of a phosphodiesterase inhibitor (slowing cAMP degradation) concurrent with a deacetylase inhibitor (prolonging histone acetylation) restored normal LTP. Importantly these paired parameter changes did not alter basal synaptic weight. A pair that simulated the effects of a phosphodiesterase inhibitor and an acetyltransferase activator was similarly effective. For both pairs strong additive synergism was present. The effect of the combination was greater than the summed effect of the separate parameter changes. These results suggest that promoting histone acetylation while simultaneously slowing the degradation of cAMP may constitute a promising strategy for restoring deficits in LTP that may be associated with learning deficits in RTS. More generally these results illustrate how the strategy of combining modeling and empirical studies may provide insights into the design of effective therapies for improving long-term synaptic plasticity and learning associated with cognitive disorders.

Epigenetic dysregulation in cognitive disorders.

Epigenetic mechanisms are not only essential for biological functions requiring stable molecular changes such as the establishment of cell identity and tissue formation, they also constitute dynamic intracellular processes for translating environmental stimuli into modifications in gene expression. Over the past decade it has become increasingly clear that both aspects of epigenetic mechanisms play a pivotal role in complex brain functions. Evidence from patients with neurodegenerative and neurodevelopmental disorders such as Alzheimer's disease and Rett syndrome indicated that epigenetic mechanisms and chromatin remodeling need to be tightly controlled for proper cognitive functions, and their dysregulation can have devastating consequences. However, because they are dynamic, epigenetic mechanisms are also potentially reversible and may provide powerful means for pharmacological intervention. This review outlines major cognitive disorders known to be associated with epigenetic dysregulation, and discusses the potential of 'epigenetic medicine' as a promising cure.

Histone deacetylase inhibitors: possible implications for neurodegenerative disorders.

During the past six years numerous studies identified histone deacetylase (HDAC) inhibitors as candidate drugs for the treatment of neurodegenerative disorders. Two major neuroprotective mechanisms of HDAC inhibitors have been identified, namely the transcriptional activation of disease-modifying genes and the correction of perturbations in histone acetylation homeostasis, which have been shown to be intimately involved in the neurodegenerative pathomechanisms of Huntington's, Parkinson's and Kennedy disease, amyotropic lateral sclerosis, Rubinstein-Taybi syndrome as well as stroke. Based on the promising in vitro and in vivo analyses, clinical trials have been initiated to evaluate the safety and efficacy of HDAC inhibitors for the treatment of devastating diseases such as Huntington's disease, amyotropic lateral sclerosis and spinal muscular atrophy. Here, the authors summarize and discuss the findings on the emerging field of epigenetic therapy strategies in neurodegenerative disorders.

Rubinstein-Taybi syndrome: molecular findings and therapeutic approaches to improve cognitive dysfunction.

Rubinstein-Taybi syndrome (RTS) is a rare human genetic disorder characterized by mental retardation and physical abnormalities. Many RTS patients have a genetic mutation which has been mapped to chromosome 16p13.3, a genomic region encoding cyclic AMP (cAMP) response element binding protein (CREB) binding protein (CBP). CBP is a transcriptional co-activator that binds to CREB when the latter is phosphorylated and promotes gene transcription. CREB-dependent gene transcription has been shown to underlie long-term memory formation. In this review we will focus on recent findings regarding the biology of CBP and its role in memory formation and cognitive dysfunction in RTS. We will also review the role of CBP in other neurological disorders, including Alzheimer's disease, Huntington's disease and amyotrophic lateral sclerosis. Finally, we will discuss novel therapeutic approaches targeted to CBP/CREB function for treating the cognitive dysfunction of RTS and other neurological disorders.

A mouse model of Rubinstein-Taybi syndrome: defective long-term memory is ameliorated by inhibitors of phosphodiesterase 4.

Mice carrying a truncated form of cAMP-responsive element binding protein (CREB)-binding protein (CBP) show several developmental abnormalities similar to patients with Rubinstein-Taybi syndrome (RTS). RTS patients suffer from mental retardation, whereas long-term memory formation is defective in mutant CBP mice. A critical role for cAMP signaling during CREB-dependent long-term memory formation appears to be evolutionarily conserved. From this observation, we reasoned that drugs that modulate CREB function by enhancing cAMP signaling might yield an effective treatment for the memory defect(s) of CBP+/- mice. To this end, we designed a cell-based drug screen and discovered inhibitors of phosphodiesterase 4 (PDE4) to be particularly effective enhancers of CREB function. We extend previous behavioral observations by showing that CBP+/- mutants have impaired long-term memory but normal learning and short-term memory in an object recognition task. We demonstrate that the prototypical PDE4 inhibitor, rolipram, and a novel one (HT0712) abolish the long-term memory defect of CBP+/- mice. Importantly, the genetic lesion in CBP acts specifically to shift the dose sensitivity for HT0712 to enhance memory formation, which conveys molecular specificity on the drug's mechanism of action. Our results suggest that PDE4 inhibitors may be used to treat the cognitive dysfunction of RTS patients.

Psychopathology, GABA, and the Rubinstein-Taybi syndrome: a review and case study.

An adult female with congenital Rubinstein-Taybi syndrome (RTS) and severe mental retardation is described, who presented with symptoms of severe over-activity, short attention span, mood lability, and aggressive outbursts in a cyclical pattern, suggestive of recurrent manic-like episodes. These symptoms improved significantly with divalproex (Depakote) monotherapy. Review of the existing studies showed that 10-76% of persons with RTS may be identified with similar behavioral symptoms. We postulate other persons with RTS may respond to divalproex, and there may be some relationship between the chromosome 16p13.3 deletion and gamma-aminobutyric acid (GABA) receptor or neurotransmitter abnormalities. Recent molecular genetic studies suggest a linkage of this region to bipolar mood disorder and autism, both of which were diagnosed in this patient. Further prospective study is needed of RTS persons regarding behavioral problems, comorbid psychiatric diagnoses, and treatment responses, correlated with genetic abnormalities.

Defect of histone acetyltransferase activity of the nuclear transcriptional coactivator CBP in Rubinstein-Taybi syndrome.

CREB-binding protein (CBP) is a transcriptional coactivator that has intrinsic histone acetyltransferase (HAT) activity. CBP is the causative gene of Rubinstein-Taybi syndrome (RTS). To investigate the relationships between CBP HAT activity and RTS, we analyzed 16 RTS patients. A microdeletion was identified in one patient by fluorescent in situ hybridization analysis. Heteroallelic mutations were identified in five patients by reverse transcriptase-polymerase chain reaction-single-strand conformation polymorphism analysis and sequencing. These included a 2 bp deletion between nucleotides 4319 and 4320, an 11 bp deletion between nucleotides 4898 and 4908, a 14 bp insertion (CCTCGGTCCTGCAC) between nucleotides 5212 and 5213, a 2 bp deletion between nucleotides 5222 and 5223, and a missense mutation from guanine (G) to cytosine (C) at nucleotide 4951 that changed codon 1378 from CGG (arginine) to CCG (proline). The identical missense mutation was introduced into the recombinant mouse CBP. It abolished the HAT activity of CBP and the ability of CBP to transactivate cyclic AMP-response element binding protein (CREB), in HAT assays and in microinjection experiments, respectively. These results suggest that the loss of the HAT activity of CBP may cause RTS, as the first example of a defect of HAT activity in a human disease. Our findings raise the possibility that treatment of RTS patients with histone deacetylase inhibitors might have beneficial effects.