Alexander Franz Perhal - Research Focuses and Projects

Current Research Focuses

• G protein-coupled receptor and second messenger pharmacology
  
  My current research focuses on the elucidation of GPCR signaling mechanisms in inflammatory and other major diseases, the development of cellular assays for GPCR ligand screening and second messenger pharmacology, and the integration of in silico approaches with natural product pharmacology to identify novel bioactive compounds.
  
  G protein-coupled receptors (GPCRs) represent the largest class of cell surface receptors and account for the molecular targets of a substantial proportion of approved drugs. Their intracellular signaling cascades oEer an intricate network of eEectors, including G proteins, second messengers, G protein-coupled receptor kinases (GRKs), and β-arrestins, that control downstream cellular responses and provide diverse opportunities for pharmacological intervention.
  

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  Three core research directions within this field are currently being pursued:
  
  1.) Development and establishment of biosensor-based cellular assays for investigations of GPCR and second messenger pharmacology and ligand screening in inflammatory diseases
  
  GPCRs and downstream second messengers such as cyclic adenosine monophosphate (cAMP) are pivotal in immune cell regulation, modulating inflammatory responses through diverse signaling pathways including Gαs- and Gαi-coupled GPCRs and degrading phosphodiesterases (PDEs)¹. A major research project titled “Identifying Nature's c(h)AMPions” (→ Research Project #1: Identifying Nature's c(h)AMPions) employs a cellular screening approach combining FRET-based cAMP biosensors and reporter gene assays to identify and pharmacologically characterize novel bioactive natural compounds as modulators of important immune cell-specific GPCRs (TGR5 and GPR84) and enzymes (PDE4). Another main research project in the context of Th17 cell-mediated inflammatory diseases searches for bioactive compounds by targeting the nuclear receptor RORα/γ (→ Research Project #4: Target identification and validation in Th17 cell-mediated pathologies - RORα/γ as a molecular drug target of primulagenin A and diosgenin).
  
  2.) Elucidation of GPCR signal transduction mechanisms with pathological relevance for major cardiovascular and neurodegenerative diseases in vitro and in vivo
  
  Atherosclerosis and ensuing cardiovascular disease as well as neurodegenerative disorders such as Alzheimer’s disease, are major causes of death and morbidity in a constantly aging society with insufficient treatment options^2,3 GPCRs and their downstream signaling mediators, including GRKs and β-arrestin-mediated pathways, have emerged as novel molecular drug targets offering substantial potential for the identification of new molecular drug targets⁴. Major research projects therefore investigated the role of GRK2 in Alzheimer’s disease (→ Research Project #2: Elucidation of GPCR Signal Transduction Mechanisms with Pathological Relevance for Neurodegenerative Diseases in vitro and in vivo) and the bradykinin B2 receptor in atherosclerosis (→ Research Project #3: Elucidation of GPCR Signal Transduction Mechanisms with Pathological Relevance for Cardiovascular Diseases in vitro and in vivo).
  
  3.) In silico-guided screening for the identification of novel bioactive compounds
  
  In silico-based methods, both target- and ligand-based, oEer great potential for the pre- selection of promising compounds for testing in cellular screening efforts and can provide iterative guidance in structural optimizations to yield compounds with improved activities.⁵ These computational approaches are integrated throughout a research project targeting TGR5 as a complement to experimental pharmacological characterization (→ Research Project #5: In silico aided discovery and characterization of small-molecule TGR5 agonists and positive allosteric modulators (PAMs)).



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References:

[1] Conti, M., Richter, W., Mehats, C., Livera, G., Park, J. Y., & Jin, C. (2003). Cyclic AMP-specific PDE4 phosphodiesterases as critical components of cyclic AMP signaling. Journal of Biological Chemistry, 278(8), 5493-5496.
[2] Björkegren, J. L., & Lusis, A. J. (2022). Atherosclerosis: recent developments. Cell, 185(10), 1630-1645.
[3] Masters, C. L., Bateman, R., Blennow, K., Rowe, C. C., Sperling, R. A., & Cummings, J. L. (2015). Alzheimer's disease. Nature reviews disease primers, 1(1), 15056.
[4] Hauser, A. S., Attwood, M. M., Rask-Andersen, M., Schiöth, H. B., & Gloriam, D. E. (2017). Trends in GPCR drug discovery: new agents, targets and indications. Nature reviews Drug discovery, 16(12), 829-842.
[5] Shaker, B., Ahmad, S., Lee, J., Jung, C., & Na, D. (2021). In silico methods and tools for drug discovery. Computers in biology and medicine, 137, 104851.

Previous and Ongoing Research Projects

• 1.) Identifying Nature's c(h)AMPions: Identification and pharmacological characterization of novel natural TGR5 agonists, GPR84 antagonists and/or PDE4 inhibitors for immunomodulation in cellular models
  
  


Background: Cyclic adenosine monophosphate (cAMP) is a pivotal second messenger in immune regulation, modulating inflammatory responses through diverse signaling pathways.⁶ Natural products, with their structural diversity and bioactivity, offer a promising reservoir for novel immunomodulatory agents. This project explores the impact of selected natural compounds on intracellular cAMP levels, with a particular focus on two immune cell- specific GPCRs: TGR5 (GPBAR1) and GPR84, as well as the major cAMP-degrading enzyme, phosphodiesterase 4 (PDE4). TGR5, a bile acid receptor, is known to elevate cAMP upon activation, promoting anti-inflammatory effects⁷, while GPR84, typically associated with pro-inflammatory signaling, decreases intracellular cAMP levels⁸. The PDE4 enzyme degrades intracellular cAMP levels, and its inhibition is therefore a suitable pharmacological intervention in many inflammatory conditions⁹.
Methodology: Using a combination of a FRET cAMP biosensor and CRE-Luciferase reporter gene assays, we screened a library of natural products and derivatives for modulatory activities on TGR5, GPR84 and PDE4, respectively.
Results: In the search for TGR5 agonists, we identified LT-188A, a Leoligin-inspired synthetic lignan, with potent in vitro anti-inflammatory activity. LT-188A selectively activated TGR5 in cellular CRE-Luciferase and cAMP accumulation assays, leading to downstream inhibition of NFκB transactivation in a TGR5-dependent manner. In macrophages, it significantly reduced pro-inflammatory cytokine expression and nitric oxide production, confirming its strong anti-inflammatory eEects. The screening for potential GPR84 antagonists resulted in the identification of a lichen-derived compound with promising in vitro bioactivities. We could show that it acts as a functional GPR84 antagonist potently inhibiting GPR84- dependent neutrophil cell migration in vitro. In the search for PDE4 inhibitors, Leoligin and 167 analogues were screened for their potential PDE-inhibitory activity leading to the identification of six compounds, including Leoligin itself, to cause a significant accumulation of cAMP from which structure-activity relationships (SAR) were deduced. The most potent analogue, designated LT-104A, was further pharmacologically characterized which confirmed its anti-inflammatory activities in designated cellular models.

(Inter-)national Collaboration(s):

• Institute of Applied Synthetic Chemistry (Head: Prof. Dr. Michael Schnürch), TU Vienna, Austria
• Department of Biochemistry & Molecular Biology (Prof. Dr. Wito Richter), University of South Alabama, Frederick P. Whiddon College of Medicine, Alabama, USA


Research Output - Publication(s):

1. Perhal, A. F.*, Schwarz, P. F., Linder, T., Mihovilovic, M. D., Schnürch, M., & Dirsch, V. M. (2025). Identification and Characterization of a Leoligin-Inspired Synthetic Lignan as a TGR5 Agonist. Journal of Natural Products, 88(4), 985-995. https://doi.org/10.1021/acs.jnatprod.5c00059 (*correspondence)
2. Coffey, C.†, Perhal, A. F.†,*, Richter, W., Chen, Y., Linder, T., Schwaiger, S., ... & Dirsch, V. M. (2025). Identification of a novel PDE4 inhibitor inspired by leoligin-derived lignans. European Journal of Medicinal Chemistry, 118285. https://doi.org/10.1016/j.ejmech.2025.118285 (†contributed equally, *correspondence)
3. Alexander F. Perhal*, Judith M. Rollinger, Patrik F. Schwarz, Ya Chen, Johannes Kirchmair, Verena M. Dirsch. The Lichen depside Imbricaric Acid inhibits GPR84- dependent neutrophil migration in a lung cell model. (*correspondence) (manuscript in preparation)

Research Output - Contributions to Scientific Conferences:
• HMPPA Symposium - “Next Generation in Pharmacognosy” (03.07. – 04.07.2025, Vienna, Austria)
  1. Alexander F. Perhal, Patrik F. Schwarz, Thomas Linder, Marko D. Mihovilovic, Michael Schnürch, Verena M. Dirsch. Identifying Nature’s c(h)AMPions – Investigation of natural products on cellular cAMP levels for immunomodulation.
     
  2. Christine Coffey*, Alexander F. Perhal*, Wito Richter, Thomas Linder, Stefan Schwaiger, Marko D. Mihovilovic, Michael Schnürch, and Verena M. Dirsch. Leoligin-inspired lignan as a novel PDE4 inhibitor with anti-inflammatory activities in vitro.
     
  3. Lorenza Bertaina*, Alexander F. Perhal*, Patrik F. Schwarz*, Panagiota Stamou, Ioannis Kostakis, Maria Halabalaki, Verena M. Dirsch. Tetracyclic triterpenes from Chios Mastic Gum as dual RORγ and TGR5 modulators.
     
  4. Sigrid Adelsberger, Alexander F. Perhal, Lorenza Bertaina, Patrik F. Schwarz, Verena M. Dirsch, Judith M. Rollinger, Ulrike Grienke. 2D NMR-based biochemometrics for deciphering bioactive compounds in multicomponent herbal mixtures.
• International Congress On Natural Products Research (ICNPR)
  1. Alexander F. Perhal, Patrik F. Schwarz, Thomas Linder, Marko D. Mihovilovic, Michael Schnürch, Verena M. Dirsch. Identification of a Leoligin-inspired synthetic lignan as a novel TGR5 agonist.
     
  2. Christine Coffey*, Alexander F. Perhal*, Lorenza Bertaina, Thomas Linder, Marko D. Mihovilovic, Michael Schnürch, Verena M. Dirsch. Leoligin derivatives as novel potential Phosphodiesterase 4 inhibitors.
     
  3. Benjamin Kirchweger, Patrik F. Schwarz, Ulrike Grienke, Alexander F. Perhal, Karmen Kapp, Verena M. Dirsch, Judith M. Rollinger. Lanostane triterpenoids of Inonotus obliquus are modulators of inflammation regulators RORγ and GPBAR1.


References:

[6] Serezani, C. H., Ballinger, M. N., Aronoa, D. M., & Peters-Golden, M. (2008). Cyclic AMP: master regulator of innate immune cell function. American journal of respiratory cell and molecular biology, 39(2), 127-132.
[7] Pols, T. W., Noriega, L. G., Nomura, M., Auwerx, J., & Schoonjans, K. (2011). The bile acid membrane receptor TGR5 as an emerging target in metabolism and inflammation. Journal of hepatology, 54(6), 1263-1272.
[8] Suzuki, M., Takaishi, S., Nagasaki, M., Onozawa, Y., Iino, I., Maeda, H., ... & Oda, T. (2013). Medium-chain fatty acid-sensing receptor, GPR84, is a proinflammatory receptor. Journal of Biological Chemistry, 288(15), 10684-10691.
[9] Li H, Zuo J and Tang W (2018) Phosphodiesterase-4 Inhibitors for the Treatment of Inflammatory Diseases. Front. Pharmacol. 9:1048. doi: 10.3389/fphar.2018.01048





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• 2.) Elucidation of GPCR Signal Transduction Mechanisms with Pathological Relevance for Neurodegenerative Diseases in vitro and in vivo
  
  


Background: Neurodegenerative diseases such as Alzheimer's disease (AD) are devastating disorders with an incomplete understanding of the underlying pathogenesis and a lack of curative treatments. G protein coupled receptor kinases (GRKs) and β-arrestin-mediated signaling pathways have emerged as novel molecular drug targets oEering the potential to reduce AD burden¹⁰. In this regard, especially GRK2 has emerged as a potential target and is therefore further investigated in this pathology.
Methodology: GRK2 aggregation was analyzed in transgenic AD mouse models and in brain tissue from patients with dementia. Experiments were performed by immunohistochemical detection and quantification of serine-670-phosphorylated GRK2 (phospho-S670-GRK2) aggregates, co-immunoprecipitation assays, mitochondrial function assays, and beta- amyloid quantification. Transgenic expression of kinase-inactive GRK2-K220R and a GRK-inhibitory peptide were used to dissect functional consequences of GRK2 inactivation. Pharmacological rescue experiments with small molecules targeting GRK2 aggregation and proteasomal degradation were performed to assess therapeutic potential.
Results: Increased aggregated phospho-S670-GRK2 was identified in AD brains, induced by the two hallmark AD proteins beta-amyloid and tau protein. Aggregated phospho-S670- GRK2 triggers TOMM6 aggregation, promotes mitochondrial dysfunction, and enhances beta-amyloid accumulation. Restoration of monomeric GRK2 and proteasomal phospho- S670-GRK2 degradation by small molecules counteracted neuropathological AD features, prevented neuronal loss, and improved survival establishing targeted disruption of pathological GRK2 aggregation as a promising therapeutic strategy.

(Inter-)national Collaboration(s):

• Molecular Pharmacology Group (Head: Prof. Dr. Ursula Quitterer), Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich


Research Output - Publication(s):

1. Abd Alla, J., Perhal, A., Fu, X., Langer, A., El Faramawy, Y., & Quitterer, U. (2026). Analysis of GRK2 aggregation in the pathology of Alzheimer disease in animal models. Cell Reports Medicine, 7(4). https://doi.org/10.1016/j.xcrm.2026.102707

Research Output - Contributions to Scientific Conferences:
• FASEB SRC Conference - “G Protein-Coupled Receptor Kinases and Arrestins: Key Modulators of GPCR Signal Transduction” (21.08. – 26.08.2022, Jupiter, Florida, USA)
  1. Joshua Abd Alla, Andreas Langer, Stefan Wolf, Alexander Perhal, Ursula Quitterer. Targeting of Mitochondrial Dysfunction in the Tg2576 Alzheimer Disease Model by a GRK2 Function Modulator.
  2. Christian Weinmann, Alexander Perhal, Andreas Langer, Ursula Quitterer. Determination of GRK2 Effects on the Kinetics of beta-adrenoceptor-stimulated cAMP Signaling by an EPAC- based cAMP Biosensor
• FASEB SRC Conference “GRKs and Arrestins: From Structure to Disease” (11.06. – 17.06.2017, Saxtons River, Vermont, USA)
  1. Perhal A., AbdAlla S. and Quitterer U. Inhibition of GRK2 triggers amyloid beta generation and Tau hyperphosphorylation in experimental Alzheimer’s Disease.


References:

[10] AbdAlla, S., Lother, H., el Missiry, A., Langer, A., Sergeev, P., el Faramawy, Y., & Quitterer, U. (2009). Angiotensin II AT2 receptor oligomers mediate G-protein dysfunction in an animal model of Alzheimer disease. Journal of Biological Chemistry, 284(10), 6554-6565.




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• 3.) Elucidation of GPCR Signal Transduction Mechanisms with Pathological Relevance for Cardiovascular Diseases in vitro and in vivo
  
  


Background: Atherosclerosis and ensuing cardiovascular disease are major causes of death and morbidity in a constantly aging society with insuEicient treatment options¹¹. In the search for novel molecular drug targets and treatment options, this project focuses on the investigation of important GPCRs (e.g., the bradykinin B2 receptor) and/or downstream signaling mediators (i.e., G protein signaling, GRKs and β-arrestin signaling) as ensuing targets. In search for pathomechanisms of atherosclerosis, we investigated the impact of the B2 bradykinin receptor, Bdkrb2, on atherosclerotic lesion formation, because to date it was not clear whether the B2 bradykinin receptor is atheroprotective or atherogenic^12,13.
Methodology: The role of Bdkrb2 in atherosclerosis was studied in hypercholesterolemic apolipoprotein E (ApoE)-deficient mice that were either Bdkrb2-deficient or with transgenic expression of BDKRB2.
Results: Bdkrb2 deficiency significantly decreased atherosclerotic plaque area, whereas transgenic BDKRB2 expression enhanced lesion formation. BDKRB2-expressing mice showed elevated aortic ROS levels and reduced tetrahydrobiopterin (BH4) and nitric oxide activity, consistent with eNOS uncoupling. Downregulation of the BH4-synthesizing enzyme Gch1 was identified as a contributing mechanism, and treatment with the BH4 analog sapropterin significantly retarded plaque formation in BDKRB2-expressing mice. These findings establish the B2 bradykinin receptor as atherogenic and BH4 depletion as a key mechanistic basis for its atherosclerosis-promoting function in vivo.

(Inter-)national Collaboration(s):

• Molecular Pharmacology Group (Head: Prof. Dr. Ursula Quitterer), Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich


Research Output - Publication(s):

1. Perhal A, Wolf S, Jamous YF, Langer A, Abd Alla J and Quitterer U (2019) Increased Reactive Oxygen Species Generation Contributes to the Atherogenic Activity of the B2 Bradykinin Receptor. Front. Med. 6:32. https://doi.org/10.3389/fmed.2019.00032

Research Output - Contributions to Scientific Conferences:
• 4th German Pharm-Tox Summit (25.02 – 28.02.2019, Stuttgart, Germany)
  1. YF Jamous, A Perhal, U Quitterer, J Abd Alla. Transgenic mice with myocardium-specific expression of SCD1 develop symptoms of heart failure.
• “KININ2018CLE” (17.06. – 20.06.2018, Cleveland, Ohio, USA)
  1. AbdAlla J., Langer A., Perhal A., Quitterer U. Deficiency of the bradykinin B2 receptor decreases atherosclerotic lesion formation in ApoE knockout mice.


References:

[11] Bergheanu, S. C., Bodde, M. C., & Jukema, J. W. (2017). Pathophysiology and treatment of atherosclerosis: Current view and future perspective on lipoprotein modification treatment. Netherlands Heart Journal, 25(4), 231-242.
[12] Manolis, A. J., Marketou, M. E., Gavras, I., & Gavras, H. (2010). Cardioprotective properties of bradykinin: role of the B2 receptor. Hypertension research, 33(8), 772-777.
[13] Sharma, J. N. (2005). The kallikrein-kinin system: from mediator of inflammation to modulator of cardioprotection. Inflammopharmacology, 12(5), 591-596.




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• 4.) Target identification and validation in Th17 cell-mediated pathologies - RORα/γ as a molecular drug target of primulagenin A and diosgenin
  
  


Background: This project investigated the natural compounds primulagenin A (PGA) and diosgenin as modulators of RORγ and RORα, nuclear receptors and key transcription factors regulating pro-inflammatory Th17 cell diEerentiation and metabolism¹⁴, with the goal of identifying promising ROR inverse agonists relevant to Th17-driven autoimmune diseases such as psoriasis, inflammatory bowel disease, and multiple sclerosis¹⁵.
Methodology: Inverse agonistic potency was determined by full-length luciferase reporter gene assays, with RORγ binding confirmed by nano differential scanning fluorimetry (nanoDSF) and in silico docking combined with site-directed mutagenesis. Functional consequences were assessed by RT-qPCR of ROR target genes (IL-17A, glucose-6- phosphatase) and, for PGA, by flow cytometric analysis of Th17 differentiation assays in murine and human primary immune cells.
Results: Both primulagenin A (PGA) and diosgenin were shown to produce potent, concentration-dependent ROR inverse agonism with consistent downregulation of target gene expression and, for PGA, direct inhibition of Th17 cell differentiation was confirmed in primary human immune cells. These findings establish two RORγ inverse agonists as pharmacological tool compounds in Th17-driven inflammatory and autoimmune diseases.

(Inter-)national Collaboration(s):

• Research group “Advancing personalized medicine in Rheumatology”, Department of Medicine III, Division of Rheumatology, Medical University of Vienna (Prof. Dr. Michael Bonelli)


Research Output - Publication(s):

1. Schwarz, P. F., Perhal, A. F., Preglej, T., Breit, L., Schmetterer, K. G., Grienke, U., ... & Dirsch, V. M. (2026). Primulagenin A is a potent inverse agonist of the nuclear receptor RAR-related orphan receptor gamma (RORγ). Acta Pharmaceutica Sinica B. https://doi.org/10.1016/j.apsb.2026.03.003
2. Schwarz, P. F.†, Perhal, A. F.†*, Schöberl, L. N., Kraus, M. M., Kirchmair, J., & Dirsch, V. M. (2022). Identification of the natural steroid sapogenin diosgenin as a Direct dual-Specific RORα/γ Inverse Agonist. Biomedicines, 10(9), 2076. https://doi.org/10.3390/biomedicines10092076 (†contributed equally, *correspondence)


References:

[14] Yang, X. O., Pappu, B. P., Nurieva, R., Akimzhanov, A., Kang, H. S., Chung, Y., ... & Dong, C. (2008). T helper 17 lineage diaerentiation is programmed by orphan nuclear receptors RORα and RORγ. Immunity, 28(1), 29-39.
[15] Ivanov, I. I., McKenzie, B. S., Zhou, L., Tadokoro, C. E., Lepelley, A., Lafaille, J. J., ... & Littman, D. R. (2006). The orphan nuclear receptor RORγt directs the diaerentiation program of proinflammatory IL-17+ T helper cells. Cell, 126(6), 1121-1133.





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• 5.) In silico aided discovery and characterization of small-molecule TGR5 agonists and positive allosteric modulators (PAMs)
  
  


Background: The Takeda G protein-coupled receptor 5 (TGR5) is activated endogenously by primary and secondary bile acids¹⁶. This receptor is considered a candidate target for addressing inflammatory and metabolic disorders¹⁷. This project was conducted in close collaboration with the Kolb Lab (Marburg University) and the Selent Lab (IMIM Barcelona), two internationally recognized groups specializing in computational GPCR pharmacology and structure-based drug discovery, establishing a productive partnership in in silico GPCR methods with in vitro validations in suitable cellular assays.
Methodology: In this project, we have targeted TGR5 with structure-based in silico methods for ligand finding using the recently solved experimental structures¹⁸, as well as structures obtained from molecular dynamics (MD) simulations. Predicted compounds were validated in in vitro cellular assays, i.e. cAMP accumulation assays, luciferase reporter gene assays and site-directed mutagenesis.
Results: Through addressing the orthosteric as well as a putative allosteric site, we identified agonists and positive allosteric modulators. This project highlights the successful interplay between iterative in silico predictions and in vitro validation in cellular assays yielding both novel TGR5 orthosteric agonists as well as positive allosteric modulators (PAMs).

(Inter-)national Collaboration(s):

• Kolb Lab (Head: Prof. Dr. Peter Kolb), Pharmaceutical Chemistry, Department of Pharmacy, Marburg University, Germany
• GPCR Drug Discovery research group (Head: Jana Selent), Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), Barcelona, Spain


Research Output - Publication(s):

1. Papadopoulos, M. G. E.†, Perhal, A. F.†, Medel-Lacruz, B., Ladurner, A., Selent, J., Dirsch, V. M., & Kolb, P. (2024). Discovery and characterization of small-molecule TGR5 ligands with agonistic activity. European Journal of Medicinal Chemistry, 276, 116616. https://doi.org/10.1016/j.ejmech.2024.116616 (†contributed equally)

Research Output - Contributions to Scientific Conferences:
• 4th ERNEST Conference - "Insights from structures of signalling complexes and computational modelling on GPCR function" (12.04. - 14.04.2021)
  1. Giovanna Papadopoulos, Angela Ladurner, Alexander Perhal, Verena Dirsch, Karin A. Zipse, Peter Kolb. In silico investigation of the bile acid receptor TGR5.


References:

[16] Maruyama, T., Miyamoto, Y., Nakamura, T., Tamai, Y., Okada, H., Sugiyama, E., ... & Tanaka, K. (2002). Identification of membrane-type receptor for bile acids (M-BAR). Biochemical and biophysical research communications, 298(5), 714-719.
[17] Pols, T. W., Noriega, L. G., Nomura, M., Auwerx, J., & Schoonjans, K. (2011). The bile acid membrane receptor TGR5 as an emerging target in metabolism and inflammation. Journal of hepatology, 54(6), 1263-1272.
[18] Chen, G., Wang, X., Ge, Y., Ma, L., Chen, Q., Liu, H., ... & Ren, R. (2020). Cryo-EM structure of activated bile acids receptor TGR5 in complex with stimulatory G protein. Signal Transduction and Targeted Therapy, 5(1), 142.