Young J D, Unkeless J C, Kaback H R, Cohn Z A
Proc Natl Acad Sci U S A. 1983 Mar;80(6):1636-40. doi: 10.1073/pnas.80.6.1636.
We tested the effect of specific ligands to the mouse macrophage IgG gamma 2b/gamma 1 Fc fragment receptor (FcR) on ion permeability of plasma membrane vesicles prepared from J774 macrophages by nitrogen cavitation. The monoclonal antibody directed against IgG gamma 2b/gamma 1 FcR (gamma 2b/gamma 1 FcR), 2.4G2 IgG, and soluble and immobilized immunocomplexes induces a dramatic cation flow through plasma membrane vesicles, as measured by [3H]tetraphenylphosphonium+ accumulation. Challenge with the monovalent 2.4G2 Fab also produces an ion flow but the effect is smaller by a factor of 2, and three other monoclonal antibodies directed against major surface antigens of mouse macrophages produce no net ion flow. Membrane vesicles incubated with FcR ligands do not discriminate between Na+ and K+ and show low permeability to Ca2+. gamma 2b/gamma 1 FcR was purified by using monoclonal 2.4G2 and reconstituted into proteoliposomes. Under these circumstances, the purified receptor increased the cation permeability of the proteoliposomes in the presence of specific ligands. The data indicate that the gamma 2b/gamma 1 FcR of J774 macrophages functions as a ligand-dependent ionophore. The ion influx into macrophages mediated by the FcR may play an important role as a signal for internalization of membranes and stimulus-secretion coupling.
我们通过氮空化法制备了J774巨噬细胞来源的质膜囊泡，测试了小鼠巨噬细胞IgGγ2b/γ1 Fc片段受体（FcR）的特异性配体对其离子通透性的影响。针对IgGγ2b/γ1 FcR（γ2b/γ1 FcR）的单克隆抗体2.4G2 IgG以及可溶性和固定化免疫复合物，可诱导显著的阳离子通过质膜囊泡流动，这通过[³H]四苯基鏻⁺积累来测量。用单价的2.4G2 Fab刺激也会产生离子流动，但效果小2倍，而针对小鼠巨噬细胞主要表面抗原的其他三种单克隆抗体则不会产生净离子流动。与FcR配体孵育的膜囊泡对Na⁺和K⁺没有区分能力，对Ca²⁺的通透性较低。通过使用单克隆抗体2.4G2纯化γ2b/γ1 FcR，并将其重组到蛋白脂质体中。在这种情况下，纯化的受体在存在特异性配体时会增加蛋白脂质体的阳离子通透性。数据表明，J774巨噬细胞的γ2b/γ1 FcR作为一种依赖配体的离子载体发挥作用。由FcR介导的离子流入巨噬细胞可能作为膜内化和刺激 - 分泌偶联的信号发挥重要作用。
