Baynes R D, Shih Y J, Hudson B G, Cook J D
Department of Medicine and Biochemistry, Kansas University Medical Center, Kansas City 66160-7402.
J Lab Clin Med. 1994 Mar;123(3):407-14.
Tissue culture studies with K562 and HL60 cells have demonstrated the production of a soluble form of transferrin receptor identical to that identified in human serum. The present study was undertaken to search for membrane remnants of the truncated receptor with peptide antibodies specific for the extracellular and cytoplasmic domain of transferrin receptor. In cell membranes, a 105K remnant was identified that is consistent with truncation of one extracellular domain monomer of the transferrin receptor. In the exosomal fraction of the culture supernatant, a smaller 20K remnant consistent with truncation of both extracellular domains was also demonstrated. These findings provide evidence that soluble receptor is the product of proteolytic cleavage of intact membrane-bound transferrin receptor. Prior studies showing that the concentration of the extracellular domain in exosomes remained stable during incubation in culture supernatant suggest that this cleavage possibly occurs intracellularly.
对K562和HL60细胞进行的组织培养研究表明，可产生一种可溶性转铁蛋白受体形式，该形式与在人血清中鉴定出的转铁蛋白受体相同。本研究旨在用针对转铁蛋白受体细胞外和细胞质结构域的肽抗体寻找截短受体的膜残余物。在细胞膜中，鉴定出一个105K的残余物，这与转铁蛋白受体一个细胞外结构域单体的截短一致。在培养上清液的外泌体部分，还证实了一个较小的20K残余物，与两个细胞外结构域的截短一致。这些发现提供了证据，表明可溶性受体是完整膜结合转铁蛋白受体蛋白水解切割的产物。先前的研究表明，在外泌体中细胞外结构域的浓度在培养上清液中孵育期间保持稳定，这表明这种切割可能发生在细胞内。
