Molecular bases of defective signal transduction in the platelet P2Y12 receptor of a patient with congenital bleeding.
Article Details
- CitationCopy to clipboard
Cattaneo M, Zighetti ML, Lombardi R, Martinez C, Lecchi A, Conley PB, Ware J, Ruggeri ZM
Molecular bases of defective signal transduction in the platelet P2Y12 receptor of a patient with congenital bleeding.
Proc Natl Acad Sci U S A. 2003 Feb 18;100(4):1978-83. Epub 2003 Feb 10.
- PubMed ID
- 12578987 [ View in PubMed]
- Abstract
We have identified structural attributes required for signal transduction through a seven-transmembrane-domain receptor. Platelets from a patient (AC) with a congenital bleeding disorder had normal shape change but reduced and reversible aggregation in response to 4 microM ADP, similar to normal platelets with blocked P2Y(12) receptor. The response to 20 microM ADP, albeit still decreased, was more pronounced and was reduced by a P2Y(12) antagonist, indicating some residual receptor function. ADP failed to lower the adenylyl cyclase activity stimulated by prostaglandin E(1) in the patient's platelets, even though the number and affinity of 2-methylthioadenosine 5'-[(33)P]diphosphate-binding sites was normal. Analysis of the patient's P2Y(12) gene revealed a G-to-A transition in one allele, changing the codon for Arg-256 in the sixth transmembrane domain to Gln, and a C-to-T transition in the other allele, changing the codon for Arg-265 in the third extracellular loop to Trp. Neither mutation interfered with receptor surface expression but both altered function, since ADP inhibited the forskolin-induced increase of cAMP markedly less in cells transfected with either mutant P2Y(12) as compared with wild-type receptor. These studies delineate a region of P2Y(12) required for normal function after ADP binding.