scholarly journals Extracellular Calcium Receptor as a Target for Glutathione and Its Derivatives

2022 ◽  
Vol 23 (2) ◽  
pp. 717
Author(s):  
Thomas Goralski ◽  
Jeffrey L. Ram
Keyword(s):  
Redox Regulation ◽  
Binding Pocket ◽  
Extracellular Calcium ◽  
Binding Energies ◽  
Glutathione Disulfide ◽  
Calcium Sensing Receptor ◽  
Calcium Receptor ◽  
New Class ◽  
Calcium Sensing ◽  
Naturally Occurring

Extracellular glutathione (GSH) and oxidized glutathione (GSSG) can modulate the function of the extracellular calcium sensing receptor (CaSR). The CaSR has a binding pocket in the extracellular domain of CaSR large enough to bind either GSH or GSSG, as well as the naturally occurring oxidized derivative L-cysteine glutathione disulfide (CySSG) and the compound cysteinyl glutathione (CysGSH). Modeling the binding energies (ΔG) of CySSG and CysGSH to CaSR reveals that both cysteine derivatives may have greater affinities for CaSR than either GSH or GSSG. GSH, CySSG, and GSSG are found in circulation in mammals and, among the three, CySSG is more affected by HIV/AIDs and aging than either GSH or GSSG. The beta-carbon linkage of cysteine in CysGSH may model a new class of calcimimetics, exemplified by etelcalcetide. Circulating glutathionergic compounds, particularly CySSG, may mediate calcium-regulatory responses via receptor-binding to CaSR in a variety of organs, including parathyroids, kidneys, and bones. Receptor-mediated actions of glutathionergics may thus complement their roles in redox regulation and detoxification. The glutathionergic binding site(s) on CaSR are suggested to be a target for development of drugs that can be used in treating kidney and other diseases whose mechanisms involve CaSR dysregulation.

159 In vitro Characterization of Potential Pig Calcium-sensing Receptor (CaSR) Ligands and Cell Signaling Pathways Related to CaSR Activation by a Dual-luciferase Reporter Assay

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 82-83
Author(s):  
Xiaoya Zhao ◽  
Qianru Hui ◽  
Paula Azevedo ◽  
Karmin O ◽  
Chengbo Yang
Keyword(s):  
Signaling Pathways ◽  
Signaling Pathway ◽  
Binding Pocket ◽  
Extracellular Calcium ◽  
Luciferase Reporter Assay ◽  
Luciferase Reporter ◽  
Reporter Assay ◽  
Biased Agonism ◽  
Calcium Sensing ◽  
Dual Luciferase Reporter Assay

Abstract The calcium-sensing receptor (CaSR) is a pivotal regulator of calcium homeostasis. Our previous study has found that pig CaSR (pCaSR) is widely expressed in intestinal segments in weaned piglets. To characterize the activation of pCaSR by potential ligands and related cell signaling pathways, a dual-luciferase reporter assay was employed for the ligands screening and molecular docking was utilized to predict the binding mode of identified ligands. Our results showed that the dual-luciferase reporter assay system was well suited for pCaSR research and its ligand screening. The extracellular calcium activated pCaSR in a concentration-dependent manner with a half-maximal effective concentration (EC50) = 4.74 mM through the Gq/11 signaling pathway, EC50 = 2.85 mM through extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation signaling pathway, and EC50 = 2.26 mM through the Ras homolog family member A (RhoA) activation signaling pathway. Moreover, the activation of pCaSR stimulated by extracellular calcium showed biased agonism through three main signaling pathways: ERK1/2 phosphorylation signaling, Gq/11 signaling, and G12/13 signaling. Both L-Tryptophan and α-casein (90–95) could activate the pCaSR in the presence of extracellular calcium. Furthermore, we characterized the L-tryptophan binding pocket formed by pCaSR residues TRP 70, SER 147, ALA168, SER 169, SER 170, ASP 190, GLU 297, ALA 298, and ILE 416, as well as the α-casein (90–95) binding pocket formed by pCaSR residues PRO188, ASN189, GLU191, HIS192, LYS225, LEU242, ASP480, VAL486, GLY487, VAL513, and TYR514. In conclusion, similar to the human CaSR, the pCaSR also shows biased agonism through three main signaling pathways and both α-casein (90–95) and L-tryptophan are agonists for pCaSR. Furthermore, the binding sites of α-casein (90–95) and L-tryptophan are mainly located within the extracellular domain of pCaSR.

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