Greco N J, Jones G D, Tandon N N, Kornhauser R, Jackson B, Jamieson G A
Platelet Biology Department, American Red Cross, Rockville, Maryland 20855, USA.
Biochemistry. 1996 Jan 23;35(3):915-21. doi: 10.1021/bi951504q.
Previous results have shown that both GPIb and the seven transmembrane domain receptor (STDR) are required for optimal thrombin-induced platelet activation (Greco et al., 1996). Limited degradation (approximately 10%) of GPIb and the STDR by elastase reduced the Ca2+ response to 0.5 nM alpha-thrombin by only 10% whereas Serratia marcescens metalloprotease reduced the Ca2+ response by 80% and fully abrogated high-affinity thrombin binding and aggregation. vWF/ristocetin-induced agglutination was only slightly reduced (20%) while Ca2+ and aggregation response to higher thrombin concentrations were retained. At increasing elastase and Serratia protease concentrations, degradation of the STDR proceeded from the amino-terminal domain, but Ca2+ responses to the tethered ligand peptide SFLLRNPNDKYEPF were not affected by either protease. These results show that both putative thrombin receptors are susceptible to protease degradation and suggest that Serratia protease is able to differentiate the GPIb-mediated events associated with thrombin activation from those associated with ristocetin-induced agglutination.
先前的结果表明，糖蛋白Ib（GPIb）和七跨膜结构域受体（STDR）都是凝血酶诱导血小板最佳活化所必需的（Greco等人，1996年）。弹性蛋白酶对GPIb和STDR进行有限程度的降解（约10%），可使对0.5 nM α-凝血酶的Ca2+反应仅降低10%，而粘质沙雷氏菌金属蛋白酶可使Ca2+反应降低80%，并完全消除高亲和力凝血酶结合和聚集。血管性血友病因子/瑞斯托菌素诱导的凝集仅略有降低（20%），而对较高凝血酶浓度的Ca2+反应和聚集反应得以保留。随着弹性蛋白酶和粘质沙雷氏菌蛋白酶浓度的增加，STDR的降解从氨基末端结构域开始，但对拴系配体肽SFLLRNPNDKYEPF的Ca2+反应不受任何一种蛋白酶的影响。这些结果表明，两种假定的凝血酶受体都易受蛋白酶降解的影响，并提示粘质沙雷氏菌蛋白酶能够区分与凝血酶活化相关的GPIb介导的事件和与瑞斯托菌素诱导的凝集相关的事件。
