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The P2 receptors and congenital platelet function defects.
1Unit of Hematology and Thrombosis, Ospedale San Paolo, Department of Medicine, Surgery and Dentistry, DMCO University of Milano, Via di Rudini 8, 20142 Milan, Italy. marco.cattaneo@unimi.it
Seminars in Thrombosis and Hemostasis
|April 27, 2005
Summary
Platelet P2Y12 receptors are crucial for ADP-induced aggregation. Genetic mutations in P2Y12 cause dysfunctional platelets and bleeding disorders, identified in a patient with specific missense mutations.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Platelets have P2Y1 (ADP) and P2X1 (ATP) receptors, with P2Y12 (ADP) mediating sustained aggregation and secretion potentiation.
- Full platelet aggregation requires the combined action of P2Y1 and P2Y12 receptors.
- Previous studies identified severe P2Y12 deficiency due to frame shift mutations.
Purpose of the Study:
- To investigate the molecular basis of a congenital bleeding disorder caused by a dysfunctional P2Y12 receptor.
- To characterize the functional impact of specific missense mutations (R256Q and R265W) in the P2Y12 receptor.
Main Methods:
- Genetic sequencing of the P2Y12 locus in a patient with a bleeding disorder.
- Creation of Chinese hamster ovary (CHO) cell lines expressing wild-type and mutant P2Y12 receptors (P2Y12(R256Q), P2Y12(R265W)).
- Assessment of receptor translocation, ADP-induced inhibition of forskolin-stimulated cyclic adenosine monophosphate (cAMP) levels.
Main Results:
- A patient was identified as a compound heterozygote with missense mutations R256Q and R265W in the P2Y12 receptor.
- Mutations did not prevent P2Y12 receptor translocation to the cell surface.
- Mutant P2Y12 receptors showed significantly reduced ability to inhibit cAMP production in response to ADP compared to wild-type.
Conclusions:
- The patient's bleeding disorder is attributed to a dysfunctional P2Y12 receptor caused by missense mutations.
- The TM6 and EL3 regions of the P2Y12 receptor are critical for its structure and function.
- These findings elucidate the molecular mechanism underlying P2Y12-related platelet dysfunction.