Exploring the Ligand-Protein Networks in Traditional Chinese Medicine: Current Databases, Methods, and Applications

The traditional Chinese medicine (TCM), which has thousands of years of clinical application among China and other Asian countries, is the pioneer of the "multicomponent-multitarget" and network pharmacology. Although there is no doubt of the efficacy, it is difficult to elucidate convincing underlying mechanism of TCM due to its complex composition and unclear pharmacology. The use of ligand-protein networks has been gaining significant value in the history of drug discovery while its application in TCM is still in its early stage. This paper firstly surveys TCM databases for virtual screening that have been greatly expanded in size and data diversity in recent years. On that basis, different screening methods and strategies for identifying active ingredients and targets of TCM are outlined based on the amount of network information available, both on sides of ligand bioactivity and the protein structures. Furthermore, applications of successful in silico target identification attempts are discussed in detail along with experiments in exploring the ligand-protein networks of TCM. Finally, it will be concluded that the prospective application of ligand-protein networks can be used not only to predict protein targets of a small molecule, but also to explore the mode of action of TCM

Exploring the Ligand-Protein Networks in Traditional Chinese Medicine: Current Databases, Methods, and Applications

The traditional Chinese medicine (TCM), which has thousands of years of clinical application among China and other Asian countries, is the pioneer of the “multicomponent-multitarget” and network pharmacology. Although there is no doubt of the efficacy, it is difficult to elucidate convincing underlying mechanism of TCM due to its complex composition and unclear pharmacology. The use of ligand-protein networks has been gaining significant value in the history of drug discovery while its application in TCM is still in its early stage. This paper firstly surveys TCM databases for virtual screening that have been greatly expanded in size and data diversity in recent years. On that basis, different screening methods and strategies for identifying active ingredients and targets of TCM are outlined based on the amount of network information available, both on sides of ligand bioactivity and the protein structures. Furthermore, applications of successful in silico target identification attempts are discussed in detail along with experiments in exploring the ligand-protein networks of TCM. Finally, it will be concluded that the prospective application of ligand-protein networks can be used not only to predict protein targets of a small molecule, but also to explore the mode of action of TCM

Melatonin receptor depletion suppressed hCG-induced testosterone expression in mouse Leydig cells

Abstract Melatonin receptors MT1 and MT2 (genes officially named MTNR1A and MTNR1B, respectively) play crucial roles in melatonin-mediated regulation of circadian rhythms, the immune system, and control of reproduction in seasonally breeding animals. In this study, immunolocalization assay showed that MT1 and MT2 are highly expressed in Leydig cell membrane. To understand the biological function of melatonin receptors in hCG-induced testosterone synthesis, we generated melatonin receptor knockdown cells using specific siRNA and performed testosterone detection after hCG treatment. We found that knockdown of melatonin receptors, especially MTNR1A, led to an obvious decrease (> 60%) of testosterone level. Our further study revealed that knockdown of melatonin receptors repressed expression, at both the mRNA level and the protein level, of key steroidogenic genes, such as p450scc, p450c17 and StAR, which are essential for testosterone synthesis. hCG triggered endoplasmic reticulum (ER) stress to regulate steroidogenic genes’ expression and apoptosis. To further investigate the potential roles of melatonin receptors in hCG-induced regulation of ER stress and apoptosis, we examined expression of some crucial ER stress markers, including Grp78, Chop, ATF4, Xbp1, and IRE1. We found that inhibition of melatonin receptors increased hCG-induced expression of Grp78, Chop and ATF4, but not Xbp1 and IRE1, suggesting that hCG may modulate IRE1 signaling pathways in a melatonin receptor-dependent manner. In addition, our further data showed that knockdown of MTNR1A and MTNR1B promoted hCG-induced expression of apoptosis markers, including p53, caspase-3 and Bcl-2. These results suggested that the melatonin receptors MTNR1A and MTNR1B are essential to repress hCG-induced ER stress and cell apoptosis. Our studies demonstrated that the mammalian melatonin receptors MT1 and MT2 are involved in testosterone synthesis via mediating multiple cell pathways