Zen Qin, Batchvarova Milena, Twyman Christina A, Eyler Christine E, Qiu Huiling, De Castro Laura M, Telen Marilyn J
Division of Hematology, Department of Medicine, Duke University Medical Center and Duke Comprehensive Sickle Cell Center, Durham, North Carolina 27710, USA.
Am J Hematol. 2004 Feb;75(2):63-72. doi: 10.1002/ajh.10442.
Red blood cells from patients with sickle cell disease (SS RBC) adhere to laminin and over-express the high-affinity laminin receptor basal cell adhesion molecule/Lutheran protein (B-CAM/LU). This receptor has recently been shown to undergo activation in vitro through a protein kinase A-dependent mechanism. Low-density SS RBC express two-thirds more B-CAM/LU than high-density SS RBC. However, high-density SS RBC have been identified as most adherent to laminin under flow conditions. We investigated the ability of low- and high-density SS RBC to interact with laminin under various conditions and explored factors that might be responsible for the differences in B-CAM/LU-laminin interaction between high- and low-density SS RBC. We confirmed that high-density SS RBC adhere to laminin more strongly than low-density SS RBC under flow conditions. However, low-density SS RBC bind soluble laminin most strongly and are the most adherent to laminin under static conditions. Soluble recombinant Lutheran extracellular domain protein completely blocked SS RBC adhesion to laminin under both static and flow conditions. The protein kinase A inhibitor 14-22 amide inhibited adhesion to laminin during flow by high-density SS RBC from patients with strongly adherent cells but had no effect on adhesion observed after a static phase. Deletion of the cytoplasmic domain of B-CAM as well as mutation of the juxtamembranous tyrosine residue failed to reduce B-CAM-mediated adhesion to laminin by transfected MEL cells. These studies confirm that B-CAM/LU is the most critical receptor mediating adhesion to laminin under both static and flow conditions. Dense SS RBC are most adherent to laminin despite bearing fewer laminin receptors, apparently due to a reversible protein kinase A-dependent process that is unlikely to involve direct phosphorylation of B-CAM/LU. Our results also suggest that the nature of the interaction of B-CAM/LU with laminin may be different under static and flow conditions.
镰状细胞病患者的红细胞（SS RBC）可黏附于层粘连蛋白，并过度表达高亲和力层粘连蛋白受体基底细胞黏附分子/路德蛋白（B-CAM/LU）。最近研究表明，该受体可通过蛋白激酶A依赖机制在体外被激活。低密度SS RBC表达的B-CAM/LU比高密度SS RBC多三分之二。然而，高密度SS RBC已被确定为在流动条件下对层粘连蛋白黏附性最强的细胞。我们研究了低密度和高密度SS RBC在不同条件下与层粘连蛋白相互作用的能力，并探讨了可能导致高密度和低密度SS RBC之间B-CAM/LU-层粘连蛋白相互作用差异的因素。我们证实，在流动条件下，高密度SS RBC比低密度SS RBC更强烈地黏附于层粘连蛋白。然而，低密度SS RBC与可溶性层粘连蛋白结合最强烈，并且在静态条件下对层粘连蛋白的黏附性最强。可溶性重组路德细胞外结构域蛋白在静态和流动条件下均能完全阻断SS RBC对层粘连蛋白的黏附。蛋白激酶A抑制剂14-22酰胺可抑制强黏附细胞患者的高密度SS RBC在流动过程中对层粘连蛋白的黏附，但对静态期后的黏附无影响。删除B-CAM的胞质结构域以及近膜酪氨酸残基的突变均未能降低转染的MEL细胞中B-CAM介导的对层粘连蛋白的黏附。这些研究证实，B-CAM/LU是在静态和流动条件下介导对层粘连蛋白黏附的最关键受体。尽管致密的SS RBC携带的层粘连蛋白受体较少，但它们对层粘连蛋白的黏附性最强，这显然是由于一个可逆的蛋白激酶A依赖过程，该过程不太可能涉及B-CAM/LU的直接磷酸化。我们的结果还表明，B-CAM/LU与层粘连蛋白相互作用的性质在静态和流动条件下可能有所不同。
