Point mutation in the mouse P2X7 receptor affects intercellular calcium waves in astrocytes

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Intercellular calcium waves (ICWs) in astrocytes are crucial for intercellular communication.
• Purinergic P2 receptors and gap junctions mediate ICW transmission, influenced by ATP release.
• The P2X7 receptor (P2X7R) and Pannexin1 (Panx1) channels are implicated in amplifying ICW spread via ATP release.

Purpose of the Study:

• To investigate the role of a P2X7R C-terminal point mutation (P451L) in modulating P2X7R-Panx1 complex function.
• To elucidate the signal transduction pathways involved in P2X7R-mediated ICW spread in astrocytes.

Main Methods:

• Comparison of P2X7R-Panx1 complex properties in astrocytes from wild-type (Balb/C) and P451L mutant (C57Bl/6) mice.
• Utilized electrophysiology, biochemistry, pharmacology, and fluorescence imaging.
• Tested the effects of a Src tyrosine kinase inhibitor (PP2) and a P2X7R-specific peptide.

Main Results:

• The P451L mutation in P2X7R attenuated Panx1 currents, reduced ATP release, and decreased the spread distance of ICWs.
• Inhibition of Src tyrosine kinase activity mimicked the effects of the P451L mutation on Panx1 currents and ICW spread.
• A peptide mimicking the mutated region of P2X7R also reduced Panx1 currents and ICW spread.

Conclusions:

• The P451L mutation impairs P2X7R-mediated Panx1 channel function, thereby reducing astrocyte-to-astrocyte calcium signaling.
• Src family tyrosine kinases are involved in the initial steps of Panx1 channel activation downstream of P2X7R stimulation.
• This study reveals a novel mechanism regulating intercellular calcium wave propagation in astrocytes.