We previously demonstrated that the human calcium-sensing receptor (CaR) is allosterically activated by L-amino acids (Conigrave, A. D., Quinn, S. J., and Brown, E. M. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 4814-4819). However, the domain-based location of amino acid binding has been uncertain. We now show that the Venus Fly Trap (VFT) domain of CaR, but none of its other major domains, is required for amino acid sensing. Several constructs were informative when expressed in HEK293 cells. First, the wild-type CaR exhibited allosteric activation by L-amino acids as previously observed. Second, two CaR-mGlu chimeric receptor constructs that retained the VFT domain of CaR, one containing the extracellular Cys-rich region of CaR and the other containing the Cys-rich region of the rat metabotropic glutamate type-1 (mGlu-1) receptor, together with the rat mGlu-1 transmembrane region and C-terminal tail, retained amino acid sensing. Third, a CaR lacking residues 1-599 of the N-terminal extracellular head but retaining an intact CaR transmembrane region and a functional but truncated C terminus (headless-T903 CaR) failed to respond to L-amino acids but retained responsiveness to the type-II calcimimetic NPS R-467. Finally, a T903 CaR control that retained an intact N terminus also retained L-amino acid sensing. Taken together, the data indicate that the VFT domain of CaR is necessary for L-amino acid sensing and are consistent with the hypothesis that the VFT domain is the site of L-amino acid binding. The findings support the concept that the mGlu-1 amino acid binding site for L-glutamate is conserved as an L-amino acid binding site in its homolog, the CaR.
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http://dx.doi.org/10.1074/jbc.M406164/200 | DOI Listing |
Int J Biol Macromol
December 2024
Department of Emergency Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China. Electronic address:
Antibiotic abuse has led to an increasingly serious risk of antimicrobial resistance, developing alternative antimicrobials to combat this alarming issue is urgently needed. Rhesus theta defensin-1 (RTD-1) is a theta-defensin contributing to broad-spectrum bactericidal activity via the mechanisms of membrane perturbation. Intriguingly, human defensin-6 (HD6), an enteric defensin secreted by Paneth cells without direct bactericidal effect, could self-assembled into fibrous networks to trap enteric pathogens for assistance of innate immunity.
View Article and Find Full Text PDFMol Cell Biochem
December 2024
Faculty of Life Sciences and Biotechnology, South Asian University, Rajpur Road, Maidan Garhi, New Delhi, India.
J Am Chem Soc
December 2024
School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia.
Ecotoxicol Environ Saf
November 2024
College of Veterinary Medicine, Hunan Agricultural University, Changsha 410125, China. Electronic address:
The T-2 toxin is a frequent contaminant in the global environment and agricultural production. Existing evidence suggests that the ingested T-2 toxin can enter the brain and exhibit neurotoxicity. However, it is still unknown whether T-2 toxin causes the depression-like behaviors.
View Article and Find Full Text PDFJ Transl Med
November 2024
Institute of Digestive Diseases, Shanghai University of Traditional Chinese Medicine, 725 South Wanping Road, Shanghai, 200032, China.
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