Tino M J, Wright J R
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA.
Am J Respir Cell Mol Biol. 1999 Apr;20(4):759-68. doi: 10.1165/ajrcmb.20.4.3439.
Glycoprotein-340 (gp-340) was first identified as a surfactant protein (SP)-D-binding molecule purified from lung lavage of patients with alveolar proteinosis (Holmskov, et al., J. Biol. Chem. 1997;272:13743). In purifying SP-A from proteinosis lavage, we isolated a protein that copurifies with SP-A and SP-D and that was later found by protein sequencing to be gp-340. We have shown that soluble gp-340 binds SP-A in a calcium-dependent manner independent of the lectin activity of SP-A. To examine the functional significance of this interaction, we tested the ability of soluble gp-340 to block SP-A binding to and stimulation of the chemotaxis of alveolar macrophages. We found that gp-340 does not affect the binding of SP-A to alveolar macrophages over a wide range of SP-A concentrations, nor does it inhibit the ability of SP-A to stimulate macrophage chemotaxis. We also found that gp-340 alone stimulates the random migration (chemokinesis) of alveolar macrophages in a manner independent of SP-A-stimulated chemotaxis. These results suggest that gp-340 is not a cell-surface receptor necessary for SP-A stimulation of chemotaxis, and show that gp-340 can directly affect macrophage function.
糖蛋白-340（gp-340）最初被鉴定为一种从肺泡蛋白沉积症患者的肺灌洗物中纯化出来的表面活性蛋白（SP）-D结合分子（霍尔姆斯科夫等人，《生物化学杂志》，1997年；272:13743）。在从蛋白沉积症灌洗物中纯化SP-A时，我们分离出一种与SP-A和SP-D共纯化的蛋白，后来通过蛋白质测序发现它是gp-340。我们已经表明，可溶性gp-340以钙依赖的方式结合SP-A，且不依赖于SP-A的凝集素活性。为了研究这种相互作用的功能意义，我们测试了可溶性gp-340阻断SP-A与肺泡巨噬细胞结合以及刺激其趋化性的能力。我们发现，在广泛的SP-A浓度范围内，gp-340不影响SP-A与肺泡巨噬细胞的结合，也不抑制SP-A刺激巨噬细胞趋化性的能力。我们还发现，单独的gp-340以不依赖于SP-A刺激趋化性的方式刺激肺泡巨噬细胞的随机迁移（化学增活作用）。这些结果表明，gp-340不是SP-A刺激趋化性所必需的细胞表面受体，并表明gp-340可直接影响巨噬细胞功能。
