Cutting Edge: A Natural P451L Mutation in the Cytoplasmic Domain Impairs the Function of the Mouse P2X7 Receptor

Abstract

The P2X7 receptor (P2X7R) is an ATP-gated channel that mediates apoptosis of cells of the immune system. The capacity of P2X7R to form large pores depends on its large cytoplasmic tail, which harbors a putative TNFR-related death domain. Previous transfection studies indicated that mouse P2X7R forms pores much less efficiently than its counterparts from humans and rats. In this study, we demonstrate that an allelic mutation (P451L) in the predicted death domain of P2X7R confers a drastically reduced sensitivity to ATP-induced pore formation in cells from some commonly used strains of mice, i.e., C57BL/6 and DBA/2. In contrast, most other strains of mice, including strains derived from wild mice, carry P451 at this position as do rats and humans. The effects of the P451L mutation resemble those of the E496A mutation in human P2X7R. These P2X7R mutants may provide useful tools to decipher the molecular mechanisms leading to pore formation.

NAD+ and ATP Released from Injured Cells Induce P2X7-Dependent Shedding of CD62L and Externalization of Phosphatidylserine by Murine T Cells

“…In this context it is important to note that common strains of laboratory mice carry allelic variants of both P2X 7 and ART2 which affect the sensitivity to endogenously released nucleotides (12,31,69). BALB/c mice express WT P2X 7 and both copies of the duplicated ART2 locus.…”

“…BALB/c mice express WT P2X 7 and both copies of the duplicated ART2 locus. C57BL/6 mice carry the 451L allelic variant of P2X 7 with impaired sensitivities to gating by ATP and ADP-ribosylation (31,32), as well as a defective ART2.1 allele, while expressing the ART2.2 locus at much higher levels than BALB/c mice (12,69). Whether the reported high sensitivity of naturally occurring regulatory T cells in C57BL/6 mice to activation of P2X 7 (70) is associated with NAD ϩ released in vivo and/or during cell preparation will be an important subject of future investigations.…”

“…Chronic activation of P2X 7 induces apoptosis and cell lysis (13). The natural allelic P451L polymorphism in the C-terminal tail of murine P2X 7 distinguishes common strains of laboratory mice (31). Wildtype (WT) P451 is expressed by BALB/c and most other strains of mice, whereas the 451L variant is expressed by C57BL/6 and DBA mice (31).…”

“…The natural allelic P451L polymorphism in the C-terminal tail of murine P2X 7 distinguishes common strains of laboratory mice (31). Wildtype (WT) P451 is expressed by BALB/c and most other strains of mice, whereas the 451L variant is expressed by C57BL/6 and DBA mice (31). The 451L variant displays normal membrane currents, but impaired pore formation (31,32).…”

“…Wildtype (WT) P451 is expressed by BALB/c and most other strains of mice, whereas the 451L variant is expressed by C57BL/6 and DBA mice (31). The 451L variant displays normal membrane currents, but impaired pore formation (31,32). Naive BALB/c T cells are very sensitive to NAD ϩ and ATP, whereas C57BL/6 T cells are less sensitive (13).…”