Two P2X1 receptor transcripts able to form functional channels are present in most human monocytes

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• P2X1 receptors are ATP-gated ion channels implicated in immune cell function.
• The presence and properties of P2X1 receptors in human monocytes require further characterization.

Purpose of the Study:

• To investigate the expression and functional properties of P2X1 receptors and its splicing variant P2X1del in human monocytes.
• To compare the characteristics of native and heterologously expressed P2X1 and P2X1del receptors.

Main Methods:

• Reverse transcription-polymerase chain reaction (RT-PCR) for mRNA expression analysis.
• Flow cytometry for receptor protein detection.
• Patch-clamp and two-electrode voltage-clamp techniques for electrophysiological recordings.
• Heterologous expression in Xenopus laevis oocytes.

Main Results:

• High expression of P2X1 (90%) and P2X1del (88%) mRNAs in human monocytes.
• P2X1 receptor immunoreactivity detected in 70% of monocytes.
• Distinct ATP sensitivities and kinetics for P2X1 (EC50=1.9±0.8µm) and P2X1del (EC50 >1000µm) channels in oocytes.
• Native P2X1 receptors in monocytes exhibited an EC50 of 6.3±0.2µm with kinetics similar to oocyte recordings.
• Both P2X1 and P2X1del currents increased in amplitude with high ATP concentrations.

Conclusions:

• This is the first study to demonstrate P2X1 and P2X1del expression in human monocytes.
• Functional homomeric P2X1del channels were characterized for the first time.
• The observed ATP-dependent current amplitude increase in P2X1/P2X1del receptors is comparable to other P2X channel subtypes.