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Structural and Functional Basis for Understanding the Biological Significance of P2X7 Receptor
Open AccessArticle

Role of Conserved Residues and F322 in the Extracellular Vestibule of the Rat P2X7 Receptor in Its Expression, Function and Dye Uptake Ability

1
Institute of Physiology, Czech Academy of Sciences, 14220 Prague, Czech Republic
2
1st Faculty of Medicine, Charles University, 12108 Prague, Czech Republic
3
Institute des Maladies Neurodégénératives, University de Bordeaux, UMR 5293, F-33000 Bordeaux, France
4
Centre National de la Recherche Scientifique, UMR 5293, F-33000 Bordeaux, France
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(22), 8446; https://doi.org/10.3390/ijms21228446
Received: 9 October 2020 / Revised: 30 October 2020 / Accepted: 5 November 2020 / Published: 10 November 2020
(This article belongs to the Special Issue Purinergic P2 Receptors: Structure and Function)
Activation of the P2X7 receptor results in the opening of a large pore that plays a role in immune responses, apoptosis, and many other physiological and pathological processes. Here, we investigated the role of conserved and unique residues in the extracellular vestibule connecting the agonist-binding domain with the transmembrane domain of rat P2X7 receptor. We found that all residues that are conserved among the P2X receptor subtypes respond to alanine mutagenesis with an inhibition (Y51, Q52, and G323) or a significant decrease (K49, G326, K327, and F328) of 2′,3′-O-(benzoyl-4-benzoyl)-ATP (BzATP)-induced current and permeability to ethidium bromide, while the nonconserved residue (F322), which is also present in P2X4 receptor, responds with a 10-fold higher sensitivity to BzATP, much slower deactivation kinetics, and a higher propensity to form the large dye-permeable pore. We examined the membrane expression of conserved mutants and found that Y51, Q52, G323, and F328 play a role in the trafficking of the receptor to the plasma membrane, while K49 controls receptor responsiveness to agonists. Finally, we studied the importance of the physicochemical properties of these residues and observed that the K49R, F322Y, F322W, and F322L mutants significantly reversed the receptor function, indicating that positively charged and large hydrophobic residues are important at positions 49 and 322, respectively. These results show that clusters of conserved residues above the transmembrane domain 1 (K49–Y51–Q52) and transmembrane domain 2 (G326–K327–F328) are important for receptor structure, membrane expression, and channel gating and that the nonconserved residue (F322) at the top of the extracellular vestibule is involved in hydrophobic inter-subunit interaction which stabilizes the closed state of the P2X7 receptor channel. View Full-Text
Keywords: P2X7 receptor; extracellular vestibule; mutagenesis; gating; deactivation; dye uptake; HEK293T cells P2X7 receptor; extracellular vestibule; mutagenesis; gating; deactivation; dye uptake; HEK293T cells
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Rupert, M.; Bhattacharya, A.; Stillerova, V.T.; Jindrichova, M.; Mokdad, A.; Boué-Grabot, E.; Zemkova, H. Role of Conserved Residues and F322 in the Extracellular Vestibule of the Rat P2X7 Receptor in Its Expression, Function and Dye Uptake Ability. Int. J. Mol. Sci. 2020, 21, 8446.

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