Heteromeric assembly of P2X subunits

Area of Science:

• Molecular biology
• Neuroscience
• Pharmacology

Background:

• P2X receptors (P2XRs) are ubiquitous in mammalian tissues, with multiple subunits often co-expressed in single cell types.
• Unlike other ligand-gated ion channels, P2X subunits readily form functional homotrimeric channels in recombinant systems.
• Native P2XR responses often differ from homomeric channels, suggesting heterotrimerization contributes to diversity.

Purpose of the Study:

• To review P2X receptor assembly and the structure of the intersubunit ATP-binding site.
• To summarize P2XR subunit distribution in mammalian cells.
• To discuss characterized heteromeric P2XRs and their potential roles in native tissues.

Main Methods:

• Literature review of P2XR assembly, subunit distribution, and heteromeric channel characterization.
• Analysis of biochemical and functional data from heterologous co-expression studies.
• Examination of evidence for heteromeric P2XRs in native tissues.

Main Results:

• Six of seven P2X subunits form functional homotrimeric channels in vitro.
• Heterotrimerization is proposed to explain the diversity of P2XR responses in native tissues.
• While P2X2/3 heteromers are established, others remain poorly understood.

Conclusions:

• P2XR subunit assembly and heteromerization are crucial for receptor function and diversity in vivo.
• Further research is needed to elucidate the composition and function of most native P2XR heteromers.
• Pharmacological tools are being developed to distinguish between homo- and heteromeric P2XRs.