Dejager S, Mietus-Snyder M, Friera A, Pitas R E
Gladstone Institute of Cardiovascular Disease, University of California, San Francisco 94141-9100.
J Clin Invest. 1993 Aug;92(2):894-902. doi: 10.1172/JCI116664.
The bovine scavenger receptor was truncated at amino acid 266 or 310 to delete either all or part, respectively, of the collagen-like domain. The truncated receptors were inactive in the binding and internalization of acetyl (Ac) low density lipoprotein (LDL). Coexpression of truncated receptor with the native receptor dramatically reduced the percentage of cells internalizing fluorescently labeled Ac LDL, compared with cells expressing the native receptor alone. The mutant truncated at amino acid 266 was most effective in receptor inactivation, resulting in a 42% or 80% decrease in the percentage of cells expressing active receptor when transfected in a 1:1 or 1:2 molar ratio (native:mutant), respectively, with native receptor. Degradation of 125I-Ac LDL was reduced up to 90% when the native and truncated mutant receptors were coexpressed. Scavenger receptor inhibition was specific because the activity of the LDL receptor was not altered. Transient transfection of the mouse macrophage cell line P388D1 with truncated scavenger receptor resulted in a 65% decrease in the uptake and degradation of Ac LDL but did not decrease the degradation of beta-migrating very low density lipoprotein, which is LDL receptor-mediated. These results demonstrate that expression of truncated bovine scavenger receptor inactivates both the native bovine and murine scavenger receptors, producing a dominant negative phenotype in vitro.
牛清道夫受体在氨基酸266或310处被截断，分别删除全部或部分胶原样结构域。截断的受体在乙酰化（Ac）低密度脂蛋白（LDL）的结合和内化过程中无活性。与单独表达天然受体的细胞相比，截断受体与天然受体共表达显著降低了内化荧光标记的Ac LDL的细胞百分比。在氨基酸266处截断的突变体在受体失活方面最有效，当与天然受体以1:1或1:2的摩尔比（天然：突变体）转染时，表达活性受体的细胞百分比分别降低42%或80%。当天然受体和截断的突变体受体共表达时，125I-Ac LDL的降解减少高达90%。清道夫受体抑制具有特异性，因为LDL受体的活性未改变。用截断的清道夫受体瞬时转染小鼠巨噬细胞系P388D1，导致Ac LDL的摄取和降解减少65%，但未降低β迁移极低密度脂蛋白的降解，后者是由LDL受体介导的。这些结果表明，截断的牛清道夫受体的表达使天然牛清道夫受体和鼠清道夫受体均失活，在体外产生显性负性表型。
