Role of glycoproteins having affinity to GlcNAc-oligomer specific DSA lectin, Putative receptor coupled to histamine release including Gi protein pathway of mast cells.

大鼠腹膜肥大细胞有两条激活途径，一条是依赖于LGE的途径，另一条是非依赖的、百日咳毒素敏感的G蛋白(GI)途径。GlcNAc寡聚体特异性凝集素曼陀罗凝集素(DSA)是GI蛋白途径中不依赖于LGE的作用部位的激动剂之一。共聚焦荧光显微镜分析显示，DSA诱导的初始激活是细胞内钙离子浓度的一过性升高，随后是细胞骨架的组装，就像化合物48/80(48/80)一样。DSA诱导的肥大细胞活化是糖专一性的，可被其他GlcNAc特异性凝集素抑制，但不受ConA的抑制。抗激动剂凝集素与相应的糖蛋白结合，不单独激活Gi-蛋白途径，但干扰糖蛋白与DSA之间的相互作用更多的证据表明，它们具有相同的作用机制，其中涉及含有GlcNAc残基的糖蛋白。GI拮抗剂阳离子苯扎氯铵对DSA诱导的组胺释放有不可逆转的抑制作用，而阴离子聚合物肝素无此作用。然而，苯扎氯铵和非离子聚合物(肝素、去N-硫酸基肝素、聚天冬氨酸和聚谷氨酸)可抑制48/80或PE16诱导的组胺释放。唾液酸特异性凝集素(MAM)和神经氨酸酶抑制DSA、48/80、PE16、P物质和缓激肽诱导的组胺释放，因此唾液酸也起重要作用。对大鼠腹膜肥大细胞的糖蛋白进行染色。凝集素印迹法检测到至少4种对DSA、WGA和MAM有亲和力且对神经氨酸酶处理敏感的糖蛋白。其中一些可能是与组胺释放偶联的受体，包括Gi-蛋白途径。这些研究可能对开发治疗上有用的抑制剂和拮抗剂具有重要意义。较少

Rat peritoneal mast cells have two activation pathway, an lgE-dependent pathway and an lgE-independent, pertussis toxin-sensitive G-protein (Gi) pathway. GlcNAc-oligomer specific lectin Datura stramonium agglutin (DSA) is one of the agonists of the lgE-independent action sites (putative recepotor) of the Gi-protein pathway. Their initial activation induced by DSA was a transient increase of intracellular calcium concentration followed by assembly of cytoskeleton as was compound 48/80 (48/80) by the method of confocal fluorescence microscopic analysis. Mast cell activation induced by DSA was sugar-specific and inhibited by other GlcNAc-specific lectins, such as WGA, STA and LEA, but not by ConA.Antagonist lectins bound to the corresponding glycoproteins and did not activate the Gi-protein pathway by themselves, but interfered with the interaction between the glycoproteins and DSA.The basic releasers 48/80, PE16 and bradykinin additively enhanced the histamine release induced by DSA, sug … More gesting that they share the same mechanisms of action, in which glycoproteins containing GlcNAc-residues were involved. Cationic benzalkonium chloride, an antagonist of Gi, irreversively inhibited the histamine release induced by DSA, but anionic polymer haparin did not. However, the histamine release induced by 48/80 or PE16 was inhibited by benzalkonium chloride and aniomic polymers (heparin, de-N-sulfated heparin, poly-aspartic acid, and poly-glutamic acid). Sialic acid was also important, since MAM (sialic acid-specific lectin) and neuraminidase inhibited the histamine release induced by DSA, 48/80, PE16, substance P and bradykinin. We stained the glycoproteins of rat peritoneal mast cells. At least four glycoproteins with affinity to DSA, WGA and MAM, and sensitive to neuraminidase-treatment were detected by lectin-blotting. Some of them may be putative receptors coupled to histamine release including the Gi-protein pathway. These studies may have important implications of the development of therapeutically useful inhibitors and antagonists. Less