Laboratory of Cell Cultures and Cellular Engineering, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, 142290, Russia.
Cell Biochem Funct. 2012 Oct;30(7):558-62. doi: 10.1002/cbf.2831. Epub 2012 Apr 16.
Glucose-regulated protein 94 (grp94) is a major component of the endoplasmic reticulum (ER) lumen of eukaryotic cells. We showed that grp94 is released from baby hamster kidney (BHK-21) cells into a serum-free medium. The exit of grp94 into the medium was not related to the protein discharge due to cell death and was independent of de novo protein synthesis. The treatment of cells with brefeldin A and monensin, the inhibitors of the classical pathway of protein secretion, did not decrease the extracellular level of grp94, indicating that the discharge of grp94 from cells does not occur through the ER/Golgi-dependent pathway. Exosomes, membrane vesicles secreted by several cell types, were not involved in the release of grp94 from cells. Methyl-β-cyclodextrin, a substance that disrupts the lipid raft organization, considerably reduced the extracellular level of grp94, indicating that lipid rafts are involved in the liberation of grp94 from BHK-21 cells. The results suggest that BHK-21 cells release grp94 into the serum-free medium via the nonclassical secretory pathway in which lipid rafts play an important role.
葡萄糖调节蛋白 94（grp94）是真核细胞内质网（ER）腔的主要组成部分。我们表明 grp94 从幼仓鼠肾（BHK-21）细胞释放到无血清培养基中。grp94 进入培养基与细胞死亡导致的蛋白质排出无关，并且独立于新蛋白质的合成。用布雷菲德菌素 A 和莫能菌素处理细胞，这两种经典蛋白分泌途径的抑制剂，并没有降低 grp94 的细胞外水平，这表明 grp94 从细胞中的排出不是通过 ER/Golgi 依赖性途径发生的。外泌体，是几种细胞类型分泌的膜囊泡，不参与 grp94 从细胞中的释放。甲基-β-环糊精，一种破坏脂筏组织的物质，大大降低了 grp94 的细胞外水平，表明脂筏参与了 BHK-21 细胞中 grp94 的释放。结果表明，BHK-21 细胞通过非经典分泌途径将 grp94 释放到无血清培养基中，其中脂筏起着重要作用。
