Recombinant Rat P2Y purinoceptor 14 (P2ry14)

What is P2Y Purinoceptor 14 (P2ry14) and what distinguishes it from other purinergic receptors?

P2Y Purinoceptor 14 (P2ry14) is a G protein-coupled receptor (GPCR) that belongs to the P2Y12-R subfamily of P2Y receptors. Unlike many other purinergic receptors that primarily respond to adenine nucleotides, P2ry14 is activated by UDP-glucose and other UDP-sugars, as well as by UDP itself, which may be one of its most important cognate activators. P2ry14 is prominently associated with immune and inflammatory cells as well as with many epithelial tissues, suggesting its important physiological role in these systems .

How can recombinant P2ry14 be expressed and purified for research purposes?

Recombinant rat P2ry14 can be expressed in E. coli expression systems with an N-terminal His tag to facilitate purification. The purified protein is typically provided as a lyophilized powder with greater than 90% purity as determined by SDS-PAGE. For reconstitution, the protein should be briefly centrifuged prior to opening and then reconstituted in deionized sterile water to a concentration of 0.1-1.0 mg/mL. For long-term storage, it is recommended to add 5-50% glycerol (with 50% being the default final concentration) and aliquot for storage at -20°C/-80°C .

What are the optimal storage conditions for recombinant P2ry14 protein?

The recombinant protein should be stored at -20°C/-80°C upon receipt, and aliquoting is necessary for multiple use to avoid repeated freeze-thaw cycles. For working aliquots, storage at 4°C for up to one week is recommended. The storage buffer typically consists of Tris/PBS-based buffer with 6% Trehalose at pH 8.0 .

What are the primary signaling pathways activated by P2ry14?

P2ry14 primarily signals through Gi/o protein-dependent pathways. Upon activation by UDP-glucose or other UDP-sugars, P2ry14 promotes inhibition of adenylyl cyclase, resulting in decreased cAMP accumulation. This inhibition can be significant, with reports of up to 80-90% inhibition of forskolin-stimulated cAMP accumulation in P2ry14-expressing cell lines. The signaling is pertussis toxin-sensitive, confirming the involvement of Gαi/o subunits .

In addition to inhibiting adenylyl cyclase, P2ry14 activation can lead to:

• Calcium mobilization

• Activation of MAP kinase signaling pathways

• Phosphorylation of ERK1/2

These additional signaling events are also pertussis toxin-sensitive, indicating their dependence on Gi/o protein coupling .

How does P2ry14 signaling influence cellular stress responses?

P2ry14 plays a crucial role in modifying cell senescence and cell death responses to tissue stress. Under stress conditions such as radiation, aging, chemotherapy exposure, or serial bone marrow transplantation, P2ry14 deficiency leads to increased cellular senescence. This enhanced senescence coincides with:

• Increased reactive oxygen species (ROS)

• Elevated p16INK4a expression

• Hypophosphorylated retinoblastoma protein (Rb)

These effects can be inhibited by treatment with ROS scavengers or inhibitors of p38/MAPK and JNK, suggesting that P2ry14 mediates its antisenescence effects through regulation of these pathways .

How are P2ry14-deficient mouse models generated and what are their characteristics?

P2ry14-deficient mice can be generated by targeted gene deletion of the sequences encoding transmembrane domains 2-7 (TM2-TM7). One approach involves replacing the coding region of the receptor with a lacZ expression cassette, which allows for galactosidase staining of cells that endogenously express P2ry14. These mice are typically backcrossed for multiple generations (>20) into the C57BL/6J background to ensure genetic homogeneity .

P2ry14 knockout mice display no obvious phenotypic abnormalities under normal conditions when compared with heterozygous and wild-type littermates. Breeding of P2ry14 heterozygous mice results in approximately the expected Mendelian ratios of offspring, indicating that the mutation is not associated with embryonic or neonatal lethality. Basic hematological parameters including white blood cell count, red blood cell count, platelet count, and hemoglobin levels are comparable between knockout and wild-type mice .

What cell line models are suitable for studying P2ry14 function?

Several cell line models have proven useful for studying P2ry14 function:

• HEK293 cells: Human embryonic kidney cells can be stably transfected with P2ry14 using retrovirus expression systems. These cells show robust responses to UDP-glucose and other UDP-sugars, with effective inhibition of forskolin-stimulated cAMP accumulation .

• C6 rat glioma cells: These cells have proven useful for studying several Gi-coupled receptors, including P2ry14. When stably expressing P2ry14, they demonstrate up to 90% inhibition of forskolin-stimulated cAMP accumulation in response to UDP-glucose .

• RBL-2H3 mast cells: These cells naturally express P2ry14 and show calcium mobilization, MAP kinase activation, and β-hexosaminidase release in response to P2ry14 agonists .

What is the role of P2ry14 in hematopoietic stem/progenitor cell function?

P2ry14 plays a critical role in preserving hematopoietic stem/progenitor cell (HSPC) function, particularly under stress conditions. While P2ry14 deficiency shows no demonstrable effect under homeostatic conditions, its importance becomes evident under various stressors:

• Radiation stress: P2ry14-deficient HSPCs show increased senescence and compromised ability to restore hematopoiesis in irradiated mice.

• Aging: P2ry14 deficiency enhances senescence in aged animals.

• Chemotherapy: Sequential exposure to chemotherapy increases senescence in animals lacking P2ry14.

• Serial bone marrow transplantation: P2ry14-deficient cells show compromised reconstitution capacity.

P2ry14 expression appears to be associated with cell-cycle dormancy in HSPCs and is indispensable for maintaining homeostasis under stress conditions .

Is P2ry14 involved in immune and inflammatory responses?

Given its prominent expression in immune and inflammatory cells, P2ry14 likely plays significant roles in immune function. In RBL-2H3 mast cells, P2ry14 activation by UDP-glucose or selective agonists like MRS2690 leads to concentration-dependent increases in β-hexosaminidase release, suggesting a role in mast cell degranulation and potentially in allergic or inflammatory responses. The receptor's broad expression pattern in immune cells points to its importance in immunological processes, though specific roles may vary depending on the cell type and context .

What are the recommended protocols for reconstituting and handling recombinant P2ry14 protein?

For optimal handling of recombinant P2ry14 protein:

• Centrifuge the vial briefly before opening to bring contents to the bottom.

• Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL.

• For long-term storage, add glycerol to a final concentration of 5-50% (50% is typically recommended).

• Aliquot and store at -20°C/-80°C for long-term preservation.

• Avoid repeated freeze-thaw cycles as they may compromise protein integrity.

• For working stocks, store aliquots at 4°C for up to one week.

The protein is typically purified to >90% purity as determined by SDS-PAGE and can be used for applications such as SDS-PAGE analysis, functional studies, and potentially structural investigations .

How can P2ry14 expression and activity be measured in experimental settings?

Several approaches can be used to measure P2ry14 expression and activity:

• Expression analysis:

  • Quantitative RT-PCR for mRNA expression

  • Flow cytometry using specific antibodies

  • Galactosidase staining in models where lacZ replaces the P2ry14 coding region

• Functional assays:

  • cAMP accumulation assays to measure inhibition of adenylyl cyclase

  • GTP-dependent inhibition of adenylyl cyclase in membrane preparations

  • Calcium mobilization assays

  • ERK1/2 phosphorylation measurements

  • Specialized readouts in specific cell types (e.g., β-hexosaminidase release in mast cells)

• Pharmacological manipulation:

  • Pertussis toxin treatment to block Gi/o-dependent signaling

  • Application of selective agonists like MRS2690

  • UDP-glucose and other UDP-sugar stimulation

How do different UDP-sugars compare in their potency and efficacy at P2ry14?

Different UDP-sugars activate P2ry14 with varying potencies and efficacies:

• UDP-glucose: Considered the prototypical agonist with EC50 values in the range of 82-107 nM in various cellular assays.

• UDP-galactose and UDP-glucuronic acid: These show similar potencies to UDP-glucose.

• UDP-N-acetylglucosamine: Typically exhibits approximately 10-fold higher EC50 values compared to UDP-glucose, indicating lower potency.

• UDP: Recent research suggests UDP itself is a very potent agonist of P2ry14 and may be one of its most important physiological activators.

All these agonists can produce similar maximal inhibition of forskolin-stimulated cAMP accumulation, suggesting similar efficacy despite differences in potency .

What are the implications of P2ry14 in stress-induced cellular senescence mechanisms?

P2ry14 serves as a critical regulator of stress-induced cellular senescence:

• ROS regulation: P2ry14 deficiency leads to increased ROS levels under stress conditions, which can be mitigated by ROS scavengers.

• Cell cycle regulators: P2ry14 absence results in elevated p16INK4a expression and hypophosphorylated Rb, key markers of cellular senescence.

• MAPK signaling: The enhanced senescence observed in P2ry14-deficient cells can be inhibited by p38/MAPK and JNK inhibitors, suggesting these pathways mediate the senescence response.

• Tissue regeneration: The antisenescence effects of P2ry14 appear particularly important for maintaining HSPC function and hematopoietic reconstitution capacity under stress conditions.

These findings suggest that P2ry14 could be a potential therapeutic target for preventing stress-induced cellular senescence and promoting tissue regeneration in conditions like radiation injury, aging, and chemotherapy-induced damage .