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Updated: May 11, 2026
Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
Published on: May 18, 2009
The C-terminus of human nucleotide receptor P2X7 is critical for receptor oligomerization and N-linked glycosylation
Lisa E Wickert1, Joshua B Blanchette, Noelle V Waldschmidt
1Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin, USA.
Background:
The P2X7 receptor binds extracellular ATP to mediate numerous inflammatory responses and is considered a potential biomarker and therapeutic target for diverse inflammatory and neurological diseases. P2X7 contains many single nucleotide polymorphisms, including several mutations located within its intracellular C-terminal trafficking domain. Mutations within the trafficking domain result in attenuated receptor activity and cell surface presentation, but the mechanisms by which amino acid changes within this region promote altered P2X7 function have not been elucidated.
Methods And Results:
We analyzed the amino acid sequence of P2X7 for any potential trafficking signals and found that P2X7 contains putative Arg-X-Arg ER retention sequences. Alanine substitutions near or within these sequences were constructed, and we determined that single mutation of R574 and R578 but not R576 or K579 attenuates P2X7-stimulated activation of ERK1/2 and induction of the transcription factors FosB and ΔFosB. We found that mutation of R578 within the trafficking domain to the naturally occurring Gln substitution disrupts P2X7 localization at the plasma membrane and results in R578Q displaying a higher apparent molecular weight in comparison to wild-type receptor. We used the glycosidase endoglycosidase H to determine that this difference in mass is due in part to the R578Q mutant possessing a larger mass of oligosaccharides, indicative of improper N-linked glycosylation addition and/or trimming. Chemical cross-linking experiments were also performed and suggest that the R578Q variant also does not form trimers as well as wild-type receptor, a function required for its full activity.
Conclusions:
These data demonstrate the distal C-terminus of P2X7 is important for oligomerization and post-translational modification of the receptor, providing a mechanism by which mutations in the trafficking domain disrupt P2X7 activity and localization at the plasma membrane.
Insights
Mutations in the P2X7 receptor's C-terminal domain disrupt its function by affecting oligomerization and post-translational modification, impacting its localization and activity in inflammatory diseases.
Area of Science:
- Immunology
- Cell Biology
- Neuroscience
Background:
- The P2X7 receptor is a key mediator of inflammatory responses and a therapeutic target for inflammatory and neurological diseases.
- Single nucleotide polymorphisms in P2X7, particularly in its C-terminal trafficking domain, are linked to altered receptor activity and cell surface presentation.
- The precise mechanisms by which these C-terminal mutations affect P2X7 function remain unclear.
Purpose of the Study:
- To elucidate the mechanisms by which amino acid changes in the P2X7 receptor's C-terminal trafficking domain alter its function.
- To investigate the role of specific amino acid residues and potential trafficking signals within the P2X7 C-terminus.
Main Methods:
- Analysis of P2X7 amino acid sequence for potential trafficking signals, including Arg-X-Arg ER retention sequences.
- Construction of alanine substitutions near or within these sequences to assess their impact on receptor activity.
- Utilized endoglycosidase H to analyze glycosylation patterns and chemical cross-linking to evaluate receptor oligomerization.
Main Results:
- Single mutations of R574 and R578, but not R576 or K579, attenuated P2X7-stimulated ERK1/2 activation and FosB/ΔFosB induction.
- The R578Q mutation disrupted P2X7 plasma membrane localization and resulted in a higher apparent molecular weight, indicative of altered N-linked glycosylation.
- The R578Q variant showed impaired trimer formation compared to wild-type P2X7 receptor.
Conclusions:
- The distal C-terminus of the P2X7 receptor is crucial for its proper oligomerization and post-translational modification.
- Mutations within the P2X7 trafficking domain can disrupt receptor activity and plasma membrane localization through impaired oligomerization and glycosylation.
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