Tag: Japan

Merrillianin is a naturally occurring compound found in Chinese herbal medicine. In a significant milestone for drug development, researchers have succeeded in its artificial synthesis, with the potential for helping treat nervous system diseases. The compound, previously tricky to synthesize due to its complex chemical structure, was successfully produced using 30 reactions. This breakthrough paves the way for the commercial development of drugs targeting diseases such as rheumatism and neuralgia.

An avenue that scientists are currently exploring for the development of novel pharmaceuticals involves the synthesis of bioactive compounds found in Chinese herbal medicine. This collaborative effort, combining traditional knowledge with modern scientific methods, focuses on pharmaceutically relevant compounds found in medicinal plants for large-scale synthesis. An important compound in this context is merrillianin, a type of illicium sesquiterpene that was isolated in 2002 from the fruit of Illicium merrillianum, a plant that belongs to the same genus as star anise. Illicium sesquiterpenes are naturally occurring compounds which hold promise for treating nervous system diseases. However, merrillianin has a complex structure with a central arrangement of six consecutive stereogenic carbon centers, including three quaternary carbon stereogenic centers, and three rings fused to two carbons. This complexity has posed challenges for the artificial synthesis of merrillianin, leading to limited progress in its practical application since its isolation.

In a breakthrough study published in the journal Organic Letters on 31 December 2023, a research group led by Assistant Professor Takatsugu Murata and Professor Isamu Shiina from Tokyo University of Science (TUS) succeeded in synthesizing merrillianin, opening doors to its artificial synthesis almost 20 years after the compound was isolated.

“Illicium sesquiterpenes are a group of compounds that are expected to be effective against neurological diseases, but their highly oxidized and ring-fused structures have made it difficult to synthesize them artificially. However, we have synthetic technique and knowledge about the synthesis of highly complicated compounds such as taxol,” says Dr. Murata. “Therefore, we wanted to perform the world’s first artificial synthesis of merrillianin, which is expected to have anti-rheumatic activity, and create a lead compound that can contribute to the treatment of neurological diseases.”

Merrillianin can be obtained with yields as high as 80% via the Wacker-type oxidation of a dilatone. However, the challenge lies in efficiently preparing the precursor compounds for the dilatone. To address this, the researchers employed a total of 30 reaction steps, covering the synthesis of precursors to the final production of merrillianin. The process commences with the Mukaiyama aldol reaction, which involves enol silyl ether and acetaldehyde. This reaction leads to the creation of a dithioacetal, a compound that includes a quaternary carbon stereogenic center. Subsequently, the dithioacetal undergoes a series of reactions with an iodo compound, resulting in the formation of α, β-unsaturated ester possessing an aldol structure. The next steps involve a reductive intramolecular cyclization of this compound to cyclopentane, followed by an intramolecular Michael’s reaction for the formation of tricyclic dilactone with a total yield of 1.6%. Tricyclic dilactone is a key intermediate for the commercial production of a wide variety of Illicium sesquiterpene compounds, including merrillianin.

The researchers point out that if merrillianin has high bioactivity, the amount required for treatment would be very little. (According to the isolation report, 3 mg of merrillianin was isolated from 30 kg of fruit.) Interestingly, it would be possible to examine its bioactivity using the synthetic version prepared by the group.

The synthesis method also revealed the absolute configuration of merrillianin, which, so far, had only known relative configurations. The proposed synthesis method for merrillianin represents another milestone for the research group, which previously succeeded in synthesizing the naturally occurring tanzawaic acid B found in the fungus Penicillium citrinum that has the potential for developing antibiotics against multidrug-resistant bacteria.

The research group’s ongoing dedication to synthesizing compounds with interesting biological activities holds promise for future discoveries in the field of drug development. Species of the Illicium genus have been used as medicinal herbs for the treatment of conditions like rheumatoid arthritis and traumatic injuries, and the synthesis of merrillianin could also contribute to advancements in these areas. “The proposed synthesis method for merrillianin will help develop suitable drugs to treat nervous system diseases such as rheumatism, and neuralgia, improving neurological disease prognosis and enhancing patient quality of life,” concludes Prof. Shiina.

Dibenzothiophene S-oxides are important in various biochemical processes. However, their synthesis using conventional methods is not easy. Researchers from Tokyo University of Science have now developed an innovative two-step process involving a Suzuki–Miyaura coupling of 2-bromoaryl-substituted sulfinate esters, followed by intramolecular electrophilic sulfinylation. This method can facilitate the facile synthesis of polysubstituted dibenzothiophene oxides without damaging highly reactive functional groups. The resulting compounds can find applications in fields like drug development and biochemical research.

Organic compounds in the field of chemistry range from simple hydrocarbons to complex molecules, with diverse functional groups added to the main carbon backbone. These functional groups impart the compounds distinct chemical properties as well as participate in various chemical transformations, making them important precursors for the synthesis of diverse compounds. Scientists have, therefore, actively engaged in creating molecules that feature novel and highly reactive functional groups.

One such class of compounds are dibenzothiophenes and their derivatives containing S-oxide or S,S-dioxide moieties (sulfur atoms bonded to one and two oxygen atoms respectively). These compounds are of special interest in the fields of pharmaceutical sciences, materials chemistry, and chemical biology. Dibenzothiophenes consist of benzene rings fused to a thiophene ring—a five-membered ring with four carbon atoms and one sulfur atom. When dibenzothiophene S-oxides are exposed to UV light, they release atomic oxygen, which is useful for DNA cleavage and oxidation of adenosine-S’-phosphosulfate kinase, an enzyme involved in cellular processes. Additionally, the S–O bond can be activated to introduce different functional groups, enabling the creation of a wide range of molecules with diverse properties and applications. The conventional method of producing functionalized dibenzothiophene S-oxides involves thiophene ring formation followed by subsequent S-oxidation. However, this reaction is challenging to carry out.

To address this, Associate Professor Suguru Yoshida, Ms. Yukiko Kumagai, Mr. Akihiro Kobayashi, and Mr. Keisuke Nakamura from Tokyo University of Science (TUS) have developed a simple two-step method of synthesizing dibenzothiophene S-oxides. The method involves Suzuki–Miyaura coupling of 2-bromoaryl-substituted sulfinate esters, followed by an intramolecular electrophilic sulfinylation.

The details of the method, published in the journal Chemical Communications on 10 January 2024, opens possibilities for creating a variety of important sulfur-containing molecules in the life sciences that were traditionally difficult to synthesize using conventional methods.

“Dibenzothiophene oxides are attracting attention in the field of chemical biology, and several researchers have developed a reaction using dibenzothiophene oxide, which can now be synthesized using this method. We expect this research to elucidate life phenomena involving reactive oxygen species,” explains Dr. Yoshida, while talking about this study.

The Suzuki–Miyaura coupling is a widely used organic reaction between boronic acids and organic halides, leading to the formation of a new carbon–carbon bond. In the proposed method, sulfinate esters react first with arylboronic acids in the presence of a palladium catalyst. Next, the intermediate biaryl compounds are activated with Tf2O, leading to subsequent cyclization by electrophilic activation.

Compared to the conventional oxidation method of synthesizing dibenzothiophene, this innovative approach developed by Dr. Yoshida and his team can accommodate a wide range of functional groups, including highly reactive ones, enabling the synthesis of polysubstituted dibenzothiophene oxides not achievable earlier. Using the method, the researchers synthesized dibenzothiophene oxides having an o-silylaryl triflate moiety, a compound useful as an aryne generation site, but tends to get easily damaged when produced using conventional methods. The o-silylaryl triflate moiety serves as a useful reactive intermediate and can undergo various transformations to produce highly substituted arenes. The proposed method, therefore, not only simplifies the synthesis method but also opens doors for a diverse range of dibenzothiophene S-oxides and their derivatives.

The novel method is a significant step forward in the field of chemical biology. Going ahead, the researchers anticipate that these compounds can find useful applications in diverse research areas, paving the way for innovations and discoveries. “The proposed method can enable the synthesis of polysubstituted benzothiophene oxides, which are expected to be useful in a wide range of research fields,” concludes Dr. Yoshida.

Consistent manufacturing and production of monoclonal antibodies (mAbs) is critical, and their functional profiles depend on cell culture conditions. Now, researchers from Japan have investigated the role of intracellular polyamines on N-glycan profiles of mAbs. They found that polyamine depletion led to an ER stress response in CHO cells, leading to an increase in galactosylation of mAbs. Supplementation of spermidine recovered N-glycan profiles. These findings will contribute to the stable production of antibody-based drugs.

Monoclonal antibodies (mAbs) are laboratory-designed proteins that mimic the immune system’s antibodies. To date, many therapeutic mAbs belonging to the immunoglobulin G (IgG) class of antibodies, have been approved for the treatment of cancer and autoimmune diseases. Cell lines such as the Chinese hamster ovary (CHO) cells are generally used to produce mAbs. Notably, the production and manufacture of mAbs are regulated by critical quality attributes (CQAs) to ensure their safety and efficacy in treatment.

An important CQA for mAbs is the N-linked glycosylation present at a specific position (Asn297). N-linked glycans consist of N-acetylglucosamine (GlcNAc), mannose (Man), fucose (Fuc), galactose (Gal), and sialic acid. The heterogeneity of the N-linked glycan profiles of mAbs can be attributed to the different numbers and linkages of additional saccharides. The composition of N-linked glycans affects the overall therapeutic efficacy, targeting ability, and immune-specificity of these antibodies. For example, antibody-dependent cellular cytotoxicity (ADCC) is influenced by the fucosylation and galactosylation of N-linked glycans. Complement-dependent cytotoxicity (CDC) is also affected by the galactosylation and sialylation of N-linked glycans. Hence, it’s crucial to meticulously regulate N-linked glycan profiles throughout the manufacturing process because the heterogeneity of the N-linked glycan profile of mAbs depends on the cell culture duration and changes in nucleotide sugars and glycosylation enzyme levels.

Recently, Dr. Kyohei Higashi, Associate Professor at Tokyo University of Science (TUS) in Japan, along with a team of researchers including Dr. Rin Miyajima and Dr. Masahiro Komeno, conducted a study to explore the effects of polyamines on N-linked glycan profiles of mAbs in CHO DP-12 cells. Their work was made available online on November 3, 2023 in the Journal of Biotechnology.

“Because the carbohydrate structure of mAbs changes depending on the state of the cells, we were interested in investigating the relationship between intracellular polyamines and the carbohydrate structure of mAbs from CHO cells.” explained Dr. Higashi, when asked about the motivation behind the research.

Polyamines (putrescine, PUT; spermidine, SPD; and spermine, SPM) are present in millimolar concentrations in all living organisms and play essential roles in normal cell growth and differentiation. PUT, SPD, and SPM contained two, three, and four amino groups, respectively. PUT is synthesized from ornithine (ORN) by ornithine decarboxylase (ODC), a rate-limiting enzyme in the polyamine biosynthesis pathway. SPD is synthesized from putrescine by spermidine synthase, and spermine is synthesized from spermidine by spermine synthase. Intracellular polyamine levels are regulated at various steps, including synthesis, degradation, and transport, and are affected by external stimuli, aging, and diseases. Because CHO cells lack arginase activity to produce ORN from arginine, they cannot produce polyamines in serum-free media, resulting in a decrease in intracellular polyamine levels, which causes a low growth rate and cell viability during long-term cultivation.

Intracellular polyamine levels can also be decreased by treatment with α-difluoromethylornithine (DFMO), an inhibitor of ODC. The depletion of intracellular polyamines by DFMO can be reversed by the addition of SPD to the growth media of CHO cells.

Upon introducing DFMO to the CHO cells, the team observed that IgG antibody galactosylation surged, along with an increase in the levels of β1,4-galactosyl transferase 1 (B4GALT1) mRNA. This mRNA is pivotal in governing the IgG galactosylation mechanism within CHO cells. What’s more, IgG production decreased by approximately 30% in DFMO-treated cells.

Dr. Higashi hypothesized that the decrease in IgG production was a result of endoplasmic stress (ER) stress response caused by polyamine depletion. During ER stress response, protein folding ceases, resulting in the arrest of the normal function of cells. Chaperone proteins assist in the correct folding of other protein classes and play a crucial role under both normal and stress conditions. The results of the ER stress response study confirmed the increased expression levels of chaperones for glycoprotein folding, in polyamine-depleted cells.

The team further observed that upon using tunicamycin, an ER stress inducer inhibiting N-glycosylation, ER stress from polyamine depletion triggered B4GALT1 mRNA expression, increasing IgG galactosylation in CHO cells.

The ability to maintain antibody glycosylation profiles via polyamine modulation has numerous implications. Controlled glycosylation is crucial for optimizing therapeutic proteins, such as antibodies, ensuring the stable production of antibodies in a uniform manner of biological activities, and potentially decreasing the manufacturing cost. Supplementation of polyamine could be accomplished by the addition only of SPD to serum-free medium, offer an easy and costless method to maintain the glycan structure of mAbs produced by CHO cells cultured in the serum-free medium. This insight might influence cell line development and bioproduction, facilitating the creation of biosimilars.

“Introducing polyamines, particularly SPD, to serum-free culture medium for CHO cells may contribute to consistent manufacturing and quality control of antibody production. We hope that this research will contribute to the stable production of antibody drugs and lead to lower drug prices” concludes Dr. Higashi.

Data Assimilation (DA) is an important mathematical method for predicting turbulent flows for weather forecasting. However, the origins of the critical length scale, a crucial parameter in this method, and its dependence on the Reynolds number are not well understood. Now, researchers have developed a novel theoretical framework that treats DA as a stability problem to explain this parameter. This framework can contribute significantly to turbulence research and inspire novel data-driven methods to predict turbulence.

Weather forecasting is important for various sectors, including agriculture, military operations, and aviation, as well as for predicting natural disasters like tornados and cyclones. It relies on predicting the movement of air in the atmosphere, which is characterized by turbulent flows resulting in chaotic eddies of air. However, accurately predicting this turbulence has remained significantly challenging owing to the lack of data on small-scale turbulent flows, which leads to the introduction of small initial errors. These errors can, in turn, lead to drastic changes in the flow states later, a phenomenon known as the chaotic butterfly effect.

To address the challenge of limited data on small-scale turbulent flows, a data-driven method known as Data Assimilation (DA) has been employed for forecasting. By integrating various sources of information, this approach enables the inference of details about small-scale turbulent eddies from their larger counterparts. Notably, within the framework of DA methods, a crucial parameter known as the critical length scale has been identified. This critical length scale represents the point below which all relevant information about small-scale eddies can be extrapolated from the larger ones. Reynold’s number, an indicator of the turbulence level in fluid flow, plays a pivotal role in this context, with higher values suggesting increased turbulence. However, despite the consensus generated by numerous studies regarding a common value for the critical scale, an explanation of its origin and its relationship with Reynold’s number remains elusive.

To address this issue, a team of researchers, led by Associate Professor Masanobu Inubushi from the Tokyo University of Science, Japan, has recently proposed a theoretical framework. They treated the process of DA as a stability problem. “By considering this turbulence phenomenon as ‘synchronization of a small vortex by a large vortex’ and by mathematically attributing it to the ‘stability problem of synchronized manifolds,’ we have succeeded in explaining this critical scale theoretically for the first time,” explains Dr. Inubushi. The letter, published in Physical Review Letters on December 18, 2023, is co-authored by Professor Yoshitaka Saiki from Hitotsubashi University, Associate Professor Miki U. Kobayashi from Rissho University, and Professor Susumo Goto from Osaka University.

To this end, the research team employed a cross-disciplinary approach by combining chaos theory and synchronization theory. They focused on an invariant manifold, termed as the DA manifold, and conducted a stability analysis. Their findings revealed that the critical length scale is a key condition for DA; and is characterized by transverse Lyapunov exponents (TLEs), which ultimately dictate the success or failure of the DA process. Additionally, based on a recent discovery showing Reynolds number dependence of maximal Lyapunov exponent (LE) and the relation of TLEs with maximal LE, they concluded that the critical length scale increases with the Reynolds number, clarifying the Reynolds number dependence of the critical length scale.

Emphasizing the importance of these findings, Dr. Inubushi says, “This new theoretical framework has the potential to significantly advance turbulence research in critical problems such as unpredictability, energy cascade, and singularity, addressing a field that physicist Richard P. Feynman once described as ‘one of the remaining difficulties in classical physics.’”

In summary, the proposed theoretical framework not only enhances our understanding of turbulence, but also paves the way for novel data-driven methods that can enhance the accuracy and reliability of weather forecasting.

Let us hope for more accurate weather predictions soon!

Falls are a serious risk for older individuals and people with compromised balance. However, there are no convenient devices to train one’s reactive posture control against unexpected perturbations outside of clinical settings. To tackle this issue, researchers from Japan have developed a lightweight wearable device to perform balance exercises at home. The experimental results showcase the potential of this device to improve postural control, thus helping prevent falls and fall-related injuries.

Maintaining balance and posture is quite a complex skill, even though it comes naturally to most people. However, postural control tends to worsen with age due to various reasons, such as muscle weakness coupled with changes in vision and sensory input. This explains why older people are much more prone to falling and suffering fall-related injuries than younger individuals. Approximately 40% of older individuals have been reported to fall at least once a year.

In this regard, over the past few decades, scientists have found that postural control can be improved through various exercises, which in turn helps prevent falls. It is possible to train and cultivate the ability to perform compensatory postural adjustments (CPAs) to counteract the effects of unexpected external perturbations. Although scientists have come up with specialized devices to perform balance exercises involving unexpected perturbations, these machines are generally bulky, expensive, and complex to use, rendering them suitable for clinical settings only.

But could there be a more practical way to perform these exercises comfortably at home? In a recent study published in IEEE Journal of Translational Engineering in Health and Medicine on 31 August 2023, a research team led by Assistant Professor Masataka Yamamoto from Tokyo University of Science (TUS), Japan, and including Professor Hiroshi Takemura, Mr. Daiki Yoshikawa, and Mr. Taku Washida from TUS, as well as Professor Koji Shimatani from the Prefectural University of Hiroshima, explore this question. For their research, the researchers developed an innovative wearable balance exercise device (WBED) and investigated its effects on CPAs and reactive postural control.

The proposed wearable device uses two pneumatic artificial muscles (PAMs) to generate unexpected perturbations. These PAMs, which resemble a pair of hollow shoulder straps or suspenders, can be forced to extend or contract by regulating the air pressure inside them. For this purpose, the WBED includes a set of electronically controlled valves connected to a can of compressed gas. This enables a computer program or smartphone application to control the valves and quickly fill or empty either PAM with gas, producing a force that pulls the user sideways in a specific direction.

To test whether WBED can truly improve reactive postural control, the researchers recruited 18 healthy adult males and divided them randomly into two groups: WBED and sham. All participants first underwent an evaluation of reactive balance. They had to hold a tandem stance for one minute while air cylinders on both sides of the hips pushed them laterally at unpredictable moments. The participants in the WBED group then performed a few rounds of balance training using the proposed device, while the sham group underwent the same exercises without unexpected perturbation. Lastly, a second evaluation was performed to check for improvements in postural control.

The researchers measured several variables as outcomes during the evaluations, including peak displacement, time at peak displacement, peak velocity, and root mean square of the soles’ center of pressure. Notably, participants in the WBED group exhibited lower displacement and peak velocity after exercising with the device. “Our results prove that perturbation-based balance exercises using WBED immediately improve the subjects’ reactive postural control,” remarks Dr. Yamamoto, satisfied with their findings. “Wearable exercise devices, such as the proposed WBED, could contribute to the prevention of falls and fall-related injuries.”

In the near future, the proposed device could revolutionize how people with a high tendency to fall perform balance training, especially in countries with a steadily aging population like Japan. “We designed WBED to be lightweight, portable, and easy to use both at home and in clinical settings. It weighs only 0.9 kg and takes less than three minutes to put on,” highlights Dr. Yamamoto. By training regularly with WBED, older individuals and people undergoing physical therapy can efficiently improve postural control and responsiveness, which in turn would prevent falls and improve their overall health. Notably, WBED could also be useful for athletes who want to improve their balance.

Let us hope that wearable devices become a mainstay in balance training and health care monitoring, providing a boost to the Internet of Things technology!

Sodium- and potassium-ion batteries are promising next-generation alternatives to the ubiquitous lithium-ion batteries (LIBs). However, their energy density still lags behind that of LIBs. To tackle this issue, researchers from Japan explored an innovative strategy to turn hard carbon into an excellent negative electrode material. Using inorganic zinc-based compounds as a template during synthesis, they prepared nanostructured hard carbon, which exhibits excellent performance in both alternative batteries.

Lithium-ion batteries (LIBs) are, by far, the most widely used type of rechargeable batteries, spanning numerous applications. These include consumer electronics, electric vehicles (e.g., Tesla cars), renewable energy systems, and spacecrafts. Although LIBs deliver the best performance in many aspects when compared to other rechargeable batteries, they have their fair share of disadvantages. Lithium is a rather scarce resource, and its price will rise quickly with its availability going down in the future. Moreover, lithium extraction and improperly discarded LIBs pose huge environmental challenges as the liquid electrolytes commonly used in them are toxic and flammable.

The shortcomings of LIBs have motivated researchers worldwide to look for alternative energy storage technologies. Sodium (Na)-ion batteries (NIBs) and potassium-ion batteries (KIBs) are two rapidly emerging options that are cost-efficient as well as sustainable. Both NIBs and KIBs are projected to be billion-dollar industries by the end of the decade. Governments across the world, including that of the US, Austria, Hong Kong, Germany, and Australia, are promoting research and innovation in this field. Moreover, companies such as Faradion Limited, TIAMAT SAS, and HiNa Battery Technology Co. Ltd., are investing heavily in this technology. Both Contemporary Amperex Technology Co. Limited and Build Your Dreams are expected to introduce electric vehicle battery packs with NIBs soon.

Unfortunately, however, the capacity of the electrode materials used in NIBs and KIBs still lags behind that of LIBs. Against this backdrop, a research team led by Professor Shinichi Komaba from Tokyo University Science (TUS), Japan, has been working to develop groundbreaking high-capacity electrode materials for NIBs and KIBs. In their latest study, published in Advanced Energy Materials on November 9, 2023, they report a new synthesis strategy for nanostructured “hard carbon” (HC) electrodes that deliver unprecedented performance. The study was co-authored by Mr. Daisuke Igarashi, Ms. Yoko Tanaka, and Junior Associate Professor Ryoichi Tatara from TUS, and Dr. Kei Kubota from the National Institute for Materials Science (NIMS), Japan.

But what is HC and why is it useful for NIBs and KIBs? Unlike other forms of carbon, such as graphene or diamond, HC is amorphous; it lacks a well-defined crystalline structure. Additionally, it is strong and resistant. In an earlier 2021 study, Prof. Komaba and his colleagues had found a way to use magnesium oxide (MgO) as a template during the synthesis of HC electrodes for NIBs, altering their final nanostructure. The process had led to the formation of nanopores within the electrodes upon MgO removal, which, in turn, had vastly increased their capacity to store Na+ ions.

Motivated by their previous findings, the researchers explored whether compounds made from zinc (Zn) and calcium (Ca) could also be useful as nano-templates for HC electrodes. To this end, they systematically investigated different HC samples made using zinc oxide (ZnO) and calcium carbonate (CaCO3) and compared their performance with the ones synthesized using magnesium oxide (MgO).

Preliminary experiments showed that ZnO was particularly promising for the negative electrode of NIBs. Accordingly, the researchers optimized the concentration of ZnO embedded in the HC matrix during synthesis, demonstrating a reversible capacity of 464 mAh g–1 (corresponding to NaC4.8) with a high initial Coulombic efficiency of 91.7% and a low average potential of 0.18 V vs. Na+/Na.

The team achieved remarkable results by incorporating this powerful electrode material into an actual battery. “The NIB fabricated using the optimized ZnO-templated HC as the negative electrode exhibited an energy density of 312 Wh kg–1,” highlights Prof. Komaba. “This value is equivalent to the energy density of certain types of currently commercialized LIBs with LiFePO4 and graphite and is more than 1.6 times the energy density of the first NIBs (192 Wh kg–1), which our laboratory reported back in 2011.” Notably, the ZnO-templated HC also exhibited a significant capacity of 381 mAh g–1 when incorporated into a KIB, further showcasing its potential.

Taken together, the results of this study show that using inorganic nanoparticles as a template to control the pore structure may provide an effective guideline for the development of HC electrodes. “Our findings prove that HCs are promising candidates for negative electrodes as an alternative to graphite,” concludes Prof. Komaba.

In turn, this could make NIBs viable for practical applications, such as the development of sustainable consumer electronics and electric vehicles as well as low carbon footprint energy storage systems for storing energy from solar and wind farms.

G protein-coupled receptors (GPCRs) are the largest and most diverse group of cell surface proteins in humans. These receptors, which can be seen as ‘traffic directors,’ transmit signals from the outside to the inside of cells and are involved in many physiological processes. Given their prominent roles in cellular communication, cell growth, immune responses, and sensory perception, many drugs have been developed to target GPCRs, for the treatment of conditions such as asthma, allergies, depression, hypertension, and heart disease. In fact, more than 300 GPCR-related drugs are currently in clinical trials, 36% of which target over 60 novel GPCR targets without an already-approved drug. Moreover, drugs that target GPCRs account for as much as 27% of the global market share of therapeutic drugs, with aggregated sales close to US$890 billion between 2011 and 2015. Thus, any technique that could accelerate research on GPCRs is likely to trigger a large ripple effect, ultimately bringing more effective treatments to millions of people.

Today, approaches such as cryo-electron microscopy, optogenetics, computational approaches and artificial intelligence, biosensors and label-free technologies, and single-cell technologies are being explored for GPCR drug discovery and development. Among them, the single-cell approach based on yeast is one of the most useful platforms to study GPCRs. Besides its widespread application in beer and bread making, the yeast species Saccharomyces cerevisiae has a long history of being used as a host to research human derived GPCRs. Although some GPCRs can be engineered to enhance their stability and function to facilitate experiments, most GPCRs do not function well in yeast cells. This long-standing problem has greatly slowed progress in our understanding of GPCRs and the development of new drugs that target them.

Against this backdrop, a research team from Tokyo University of Science (TUS), Japan, recently came up with an innovative strategy to restore the activity of human derived GPCR human histamine 3 (H3R) in S. cerevisiae. Their study, published in Volume 13 of Scientific Reports on September 26, 2023, was led by Associate Professor Mitsunori Shiroishi and co-authored by Ms. Ayami Watanabe and Ms. Ami Nakajima, all from TUS.

“H3R is mainly expressed in the nervous system. It is involved in cognitive function, and its inhibition is associated with the therapeutic outcomes of various conditions, such as ADHD, schizophrenia, Alzheimer’s disease, and narcolepsy,” explains Dr. Shiroishi. Through preliminary experiments, the team showed that H3R becomes non-functional when expressed in yeast.

To restore its function, the research team utilized a technique called error-prone polymerase chain reaction to introduce random mutations in the H3R gene. After producing a random mutant library of H3R, they introduced modified DNA segments into yeast cells and cultivated them in the presence of an H3R agonist—a compound that binds to H3R and sets off a measurable response. By screening through multiple cultures, the researchers obtained four mutants in which the normal activity of H3R was restored. These mutants responded exclusively to a type of yeast strain that harbors certain G-chimera proteins. The mutations responsible for the restored activity were located near the amino acid sequence motifs important for GPCR activation.

This innovative approach to study GPCRs could have profound implications, particularly in the fields of medicine and cell biology. “Our research could help elucidate the function of GPCRs and may even lead to the development of drugs with fewer side effects, as well as bolster drug discovery for diseases for which there is currently no treatment,” remarks Dr. Shiroishi. There are many therapeutic areas where GPCR-targeting drugs are being actively developed, including neurological disorders like Alzheimer’s and schizophrenia, cardiovascular diseases such as hypertension and heart failure, various types of cancer, and metabolic disorders.

A deeper understanding of GPCR variations and how they impact individuals differently could also lead to new approaches to personalized medicine. Tailoring GPCR-targeted drugs to an individual’s genetic makeup and their specific disease profile may greatly improve treatment outcomes. Furthermore, generic GPCR treatments reaching a vast number of people worldwide might also become a reality, which would reduce the burden on healthcare systems.

We are certain that the findings of this study will pave the way to a healthier future for everyone.