Seiler S M, Goldenberg H J, Michel I M, Hunt J T, Zavoico G B
Department of Cardiovascular Biochemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543.
Biochem Biophys Res Commun. 1991 Dec 16;181(2):636-43. doi: 10.1016/0006-291x(91)91238-8.
Recently a thrombin receptor with a unique mechanism of activation was cloned from a megakaryocyte-like cell line (Vu et al., Cell 64:1057-1068, 1991). Thrombin cleaves a portion of this receptor creating a new N-terminus that acts as a "tethered-ligand" to activate the receptor. A thrombin receptor activating peptide (SFLLRNPNDKYEPF) homologous to the new N-terminus was shown to activate platelets. We synthesized this peptide and demonstrated that it desensitized platelets to activation by low concentrations of alpha-thrombin but not gamma-thrombin. We also synthesized a thrombin exosite inhibitor (BMS 180742) that inhibited platelet aggregation induced by low, but not high, concentrations of alpha-thrombin. In contrast, a thrombin active site inhibitor, N alpha-(2-naphthylsulfonyl-glycyl)-D,L-amidinophenylalanylpiperi dide, competitively inhibited thrombin-induced platelet aggregation. We conclude that thrombin-induced platelet activation is mediated by at least two pathways: one activated by low concentrations of alpha-thrombin and blocked by a thrombin exosite inhibitor that appears to be coupled to the "tethered-ligand" thrombin receptor, and another that is stimulated by higher concentrations of alpha-thrombin and by gamma-thrombin and does not require the thrombin exosite for activation. Both pathways are blocked by a thrombin active site inhibitor.
最近，一种具有独特激活机制的凝血酶受体从一种巨核细胞样细胞系中克隆出来（Vu等人，《细胞》64:1057 - 1068，1991）。凝血酶切割该受体的一部分，产生一个新的N端，该N端作为“拴系配体”来激活受体。一种与新N端同源的凝血酶受体激活肽（SFLLRNPNDKYEPF）被证明可激活血小板。我们合成了这种肽，并证明它能使血小板对低浓度的α - 凝血酶激活产生脱敏作用，但对γ - 凝血酶无此作用。我们还合成了一种凝血酶外位点抑制剂（BMS 180742），它能抑制低浓度而非高浓度的α - 凝血酶诱导的血小板聚集。相比之下，一种凝血酶活性位点抑制剂，Nα - (2 - 萘磺酰 - 甘氨酰) - D,L - 脒基苯丙氨酰哌啶，竞争性抑制凝血酶诱导的血小板聚集。我们得出结论，凝血酶诱导的血小板激活至少由两条途径介导：一条由低浓度的α - 凝血酶激活，并被一种似乎与“拴系配体”凝血酶受体偶联的凝血酶外位点抑制剂阻断；另一条由较高浓度的α - 凝血酶和γ - 凝血酶刺激，且激活不需要凝血酶外位点。两条途径都被凝血酶活性位点抑制剂阻断。
