Serafini-Cessi F, Malagolini N, Hoops T C, Rindler M J
Department of Experimental Pathology, University of Bologna, Italy.
Biochem Biophys Res Commun. 1993 Jul 30;194(2):784-90. doi: 10.1006/bbrc.1993.1890.
Human Tamm-Horsfall glycoprotein (T-H) is produced by renal cells of ascending limb of loop of Henle and is largely excreted in urine. N-linked glycans account for close to 30% of the weight of T-H. We studied the biosynthesis of recombinant T-H permanently expressed in HeLa cells. The conversion from the precursor (84 kDa) to the mature form (97 kDa) mainly depends on the processing of glycans from the high-mannose to polyantennary type. The conversion from precursor to mature form is very slow and the glycan structure of precursor appears to be that of a glycoprotein not yet processed by Golgi alpha 1,2 mannosidase. Since T-H has a very high number of disulfide bridges (more than 50 cysteine residues/mol) one may infer that the rate limiting step for the precursor export out of ER is the formation of a correct set of disulfide bonds. Mature T-H isolated from HeLa cells retained one N-linked chain with the high-mannose structure similarly to urinary T-H. This result indicates that the occurrence of one unprocessed high-mannose chain in mature T-H is host-cell independent and very likely related to the T-H primary structure.
人Tamm-Horsfall糖蛋白（T-H）由髓袢升支粗段的肾细胞产生，并主要经尿液排泄。N-连接聚糖占T-H重量的近30%。我们研究了在HeLa细胞中永久表达的重组T-H的生物合成。从前体（84 kDa）到成熟形式（97 kDa）的转化主要取决于聚糖从高甘露糖型到多天线型的加工。从前体到成熟形式的转化非常缓慢，前体的聚糖结构似乎是一种尚未被高尔基体α1,2-甘露糖苷酶加工的糖蛋白的结构。由于T-H有非常多的二硫键（每摩尔超过50个半胱氨酸残基），因此可以推断前体从内质网输出的限速步骤是正确二硫键的形成。从HeLa细胞中分离出的成熟T-H保留了一条具有高甘露糖结构的N-连接链，类似于尿T-H。这一结果表明，成熟T-H中一条未加工的高甘露糖链的出现与宿主细胞无关，很可能与T-H的一级结构有关。
