Rizzoli R, Bonjour J P
Department of Medicine, University Hospital of Geneva, Switzerland.
Am J Physiol. 1989 Jan;256(1 Pt 1):E80-6. doi: 10.1152/ajpendo.1989.256.1.E80.
Carbohydrate moieties of cell surface glycoproteins with an external orientation play a role in hormone recognition and/or transmembrane signal transmission. We have examined the effect of various lectins, which interact with specific cell surface glycosyl residues, and of tunicamycin, an antibiotic that inhibits glycosylation of proteins, on the adenosine 3',5'-cyclic monophosphate (cAMP) response to parathyroid hormone (PTH) in confluent cultured osteoblast-like rat osteosarcoma cells (UMR-106) and opossum kidney cells (OK cells). Incubation of both cell lines with wheat germ lectin (WGL), but not with concanavalin A, succinylated wheat germ, ricin, or soybean lectins, markedly reduced the PTH-induced cAMP production, whereas the stimulation obtained with forskolin, a compound that acts directly on the adenylate cyclase enzyme, was not affected. In contrast, tunicamycin did not cause any decrease in the cAMP response to PTH. These results indicate that the masking of sialic acid residue by WGL considerably blunted PTH-stimulated cAMP production in cultured osteoblast-like and kidney cells. An 80% inhibition of glycosylation of cell surface proteins did not appear to affect the response to PTH. Thus the functional role of this carbohydrate moiety in the PTH receptor remains to be determined.
具有外向定位的细胞表面糖蛋白的碳水化合物部分在激素识别和/或跨膜信号传递中发挥作用。我们研究了各种与特定细胞表面糖基残基相互作用的凝集素以及一种抑制蛋白质糖基化的抗生素衣霉素对汇合培养的大鼠成骨样骨肉瘤细胞（UMR-106）和负鼠肾细胞（OK细胞）中甲状旁腺激素（PTH）诱导的3',5'-环磷酸腺苷（cAMP）反应的影响。用麦胚凝集素（WGL）处理这两种细胞系，但用伴刀豆球蛋白A、琥珀酰化麦胚、蓖麻毒素或大豆凝集素处理则不会，这显著降低了PTH诱导的cAMP产生，而用直接作用于腺苷酸环化酶的化合物福斯可林获得的刺激不受影响。相反，衣霉素并未导致对PTH的cAMP反应出现任何降低。这些结果表明，WGL对唾液酸残基的掩盖显著减弱了培养的成骨样细胞和肾细胞中PTH刺激的cAMP产生。细胞表面蛋白糖基化80%的抑制似乎并未影响对PTH的反应。因此，这种碳水化合物部分在PTH受体中的功能作用仍有待确定。
