P2X7 receptor cell surface expression and cytolytic pore formation are regulated by a distal C-terminal region
2003
The importance of the cytosolic C-terminal region of the P2X7 receptor (P2X7R) is unquestioned, yet little is known about the functional domains of this region and how they may contribute to the numerous properties ascribed to this receptor. A structure-function analysis of
truncatedand single-residue-mutated P2X7 receptors was performed in
HEK-293 cellsand Xenopus oocytes. Cells expressing receptors
truncatedat residue 581 (of 595) have negligible ethidium ion uptake, whereas those expressing the P2X7R
truncatedat position 582 give wild type ethidium ion uptake suggesting that pore formation requires over 95% of the C-terminal tail. Channel function was evident even in receptors that were
truncatedat position 380 indicating that only a small portion of the cytosolic region is required for channel activity. Surprisingly,
truncationsin the region between residues 551 and 581 resulted in non-functional receptors with no detectable cell surface expression in
HEK-293 cells. A more detailed analysis revealed that mutations of single residues within this region could also abolish receptor function and cell surface expression, suggesting that this region may participate in regulating the surface expression of the pore-forming P2X7R.
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