Franck P F, Bevers E M, Lubin B H, Comfurius P, Chiu D T, Op den Kamp J A, Zwaal R F, van Deenen L L, Roelofsen B
J Clin Invest. 1985 Jan;75(1):183-90. doi: 10.1172/JCI111672.
We have previously reported that the normal membrane phospholipid organization is altered in sickled erythrocytes. More recently, we presented evidence of enhanced transbilayer movement of phosphatidylcholine (PC) in deoxygenated reversibly sickled cells (RSC) and put forward the hypothesis that these abnormalities in phospholipid organization are confined to the characteristic protrusions of these cells. To test this hypothesis, we studied the free spicules released from RSC by repeated sickling and unsickling as well as the remnant despiculated cells. The rate of transbilayer movement of PC in the membrane of deoxygenated remnant despiculated cells was determined by following the fate of 14C-labelled PC, previously introduced into the outer monolayer under fully oxygenated conditions using a PC-specific phospholipid exchange protein from beef liver. The rate of transbilayer movement of PC in the remnant despiculated cells was significantly slower than in deoxygenated native RSC and was not very much different from that in oxygenated native RSC or irreversibly sickled cells. The free spicules had the same lipid composition as the native cells, but were deficient in spectrin. These spicules markedly enhanced the rate of thrombin formation in the presence of purified prothrombinase (Factor Xa, Factor Va, and Ca2+) and prothrombin, indicating the exposure of a significant fraction of phosphatidylserine (PS) in the outer monolayer. This effect was not observed when the spicules in this assay were replaced by normal erythrocytes, deoxygenated native RSC, or a deoxygenated sample of RSC after repetitive sickling/unsickling. The results are interpreted to indicate that the destabilization of the lipid bilayer in sickled cells, expressed by the enhanced flip-flop of PC and the exposure of PS in the outer monolayer, occurs predominantly in those parts of the membrane that are in spicular form.
我们之前报道过，镰状红细胞中正常的膜磷脂组织会发生改变。最近，我们提供了证据表明，在脱氧的可逆镰状细胞（RSC）中，磷脂酰胆碱（PC）的跨膜运动增强，并提出假说，即磷脂组织的这些异常局限于这些细胞的特征性突起。为了验证这一假说，我们研究了通过反复镰变和去镰变从RSC释放的游离针状物以及残余的去针状物细胞。利用来自牛肝的PC特异性磷脂交换蛋白，在完全氧化条件下将14C标记的PC预先引入外单层，然后通过追踪其去向，测定脱氧残余去针状物细胞膜中PC的跨膜运动速率。残余去针状物细胞中PC的跨膜运动速率明显慢于脱氧天然RSC，与氧化天然RSC或不可逆镰状细胞中的速率没有太大差异。游离针状物的脂质组成与天然细胞相同，但血影蛋白不足。在存在纯化的凝血酶原酶（因子Xa、因子Va和Ca2+）和凝血酶原的情况下，这些针状物显著提高了凝血酶形成的速率，表明外单层中有相当一部分磷脂酰丝氨酸（PS）暴露。当该实验中的针状物被正常红细胞、脱氧天然RSC或反复镰变/去镰变后的RSC脱氧样品取代时，未观察到这种效应。这些结果被解释为表明，镰状细胞中脂质双层的不稳定，表现为PC的翻转增强和外单层中PS的暴露，主要发生在膜的针状部分。
Zotero 插件
