Neuronal Health
When we enhance brain-derived neurotrophic factor (BDNF) expression by interacting with specific transcription factors or enhancer elements in the BDNF gene promoter, we are exploring another therapeutic possibility. Such would increase BDNF levels, promoting synaptic plasticity and neuronal survival. The drug as such could stabilize BDNF mRNA, enhancing its translation. Acting as a positive allosteric modulator of TrkB receptors, enhancing the binding of BDNF to its receptor, may be possible. This would activate downstream signalling pathways, such as the PI3K-Akt pathway, promoting cell survival, and the MAPK-ERK pathway, enhancing synaptic plasticity and long-term potentiation (LTP). One could upregulate the expression of synaptic proteins as well, including synapsins and neuroligins, by interacting with specific transcription factors or enhancer elements in their gene promoters. Synapsins regulate the availability of synaptic vesicles for release, while neuroligins mediate synaptic adhesion and signalling. By increasing the levels of these proteins, our drug could enhance synaptic connectivity and communication between neurons. The medicine could also stabilize neuroligin-neurexin interactions at the synapse, promoting synaptic adhesion and signalling.
Furthermore, designing novel solutions could involve reducing oxidative stress by scavenging reactive oxygen species (ROS) and upregulating the expression of antioxidant enzymes, such as superoxide dismutase (SOD) and catalase, by interacting with specific transcription factors or enhancer elements in their gene promoters. This would enhance the cellular antioxidant defence system, protecting neurons from oxidative damage and improving overall neuronal health. One could also inhibit the production of pro-inflammatory cytokines, such as TNF-α, IL-1β, and IL-6, by modulating signalling pathways involved in inflammation, such as the NF-κB pathway. By reducing the levels of these cytokines, the drug would decrease neuroinflammation and create a more favourable environment for neuronal function and survival. The drug could activate anti-inflammatory pathways, such as the IL-10 signalling pathway, by acting as an agonist for IL-10 receptors. This would promote the production of anti-inflammatory cytokines and inhibit the activation of microglia and astrocytes, further reducing neuroinflammation and supporting neuronal health. Blocking the activation of the NF-κB pathway could be achieved by binding to IκB kinase (IKK) and preventing the phosphorylation and degradation of IκB, thereby inhibiting NF-κB translocation to the nucleus and reducing cytokine production.
Let us conclude our article with an optimistic tone. Recently I have been made aware how researchers at the University of California, San Diego, employed directed evolution to engineer a variant of tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin biosynthesis. The evolved TPH variant exhibited a 2.5-fold increase in catalytic efficiency compared to the wild-type enzyme. In preclinical studies using a mouse model of ASD, the engineered TPH variant was able to restore serotonin levels in the brain, leading to improvements in social interaction and repetitive behaviors. Another effort has been made, a team at the Massachusetts Institute of Technology (MIT) used directed evolution to enhance the activity and stability of tyrosine hydroxylase (TH), a key enzyme in dopamine synthesis. The evolved TH variant demonstrated a 3-fold increase in catalytic efficiency and improved thermal stability. When expressed in a mouse model of ASD, the engineered TH variant led to increased dopamine levels in the brain, resulting in reduced repetitive behaviors and improved cognitive function. Directed evolution has also been applied to enzymes involved in GABA synthesis and degradation. We have engineered variants of glutamate decarboxylase (GAD), the enzyme responsible for converting glutamate to GABA, with enhanced activity and stability. Such engineered enzymes have shown promise in preclinical models of ASD by restoring GABA levels and improving behavioral outcomes. Gene fragments from multiple TH mutants were shuffled and screened for improved activity and stability with good results. Techniques among these studies differ. In the case of the engineered BDNF variant, a fluorescence-based assay was used to screen for mutants with enhanced binding affinity to the TrkB receptor. For the neuroligin-1 variant, a cell-based assay was employed to screen for mutants with improved synaptic transmission. While the success stories mentioned above are promising, it is important to note that most of these studies have been conducted in preclinical models, such as cell lines and animal models of ASD. The translation of these findings to human clinical trials is still in progress.
Preclinical studies in a mouse model of ASD showed significant improvements in social interaction and repetitive behaviors. Interesting to note, preclinical studies in a mouse model of ASD demonstrated reduced repetitive behaviors and improved cognitive function and a phase I clinical trial to assess the safety and tolerability of this variant in humans has commenced. We could conclude the engineered BDNF variant has shown promising results in preclinical studies, with improvements in synaptic connectivity, cognitive function, and social behavior in a mouse model of ASD. A phase I/II clinical trial to evaluate the efficacy of this variant in individuals with ASD has entered recruitment phase. The neuroligin-1 variant has not yet progressed to clinical trials, but preclinical studies in a mouse model of ASD have shown increased synaptic density and improved social interaction and communication.
It seems to be the case, by targeting multiple molecular pathways and addressing the underlying neurobiological mechanisms of ASD, a drug could offer significant improvements in symptoms and quality of life for patients. More research and clinical trials would be necessary to validate these hypotheses and ensure the safety and efficacy of potential treatment. The application of directed evolution in the context of Autism Spectrum Disorder (ASD) has shown promising results in preclinical models. By understanding the detailed molecular mechanisms and employing advanced techniques we have been able to engineer enzymes and proteins with enhanced activity, stability, and specificity. Rigorous clinical trials and more research are necessary to fully realize the potential of these novel treatments.
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New approaches for the neuroimaging of gene expression
Molecular Mechanisms of Tetrahydrobiopterin Action on Neurotransmitter Release
Nuclear neurotransmitter molecular imaging of autism spectrum disorder
Encapsulation of protein in silica matrices: structural evolution on the molecular and nanoscales
Primary T‐cell‐based delivery platform for in vivo synthesis of engineered proteins
TRPA1 regulates gastrointestinal motility through serotonin release from enterochromaffin cells
Abiotic Synthetic Antibodies to Target a Specific Protein Domain and Inhibit Its Function
Construction of Protein Switches by Domain Insertion and Directed Evolution
Directed evolution for improved total secretory protein production in Escherichia coli
Active site labeling of fatty acid and polyketide acyl-carrier protein transacylases
In the light of directed evolution: pathways of adaptive protein evolution
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