Fishburn C S, Elazar Z, Fuchs S
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
J Biol Chem. 1995 Dec 15;270(50):29819-24. doi: 10.1074/jbc.270.50.29819.
The D2 dopamine receptor exists in two alternatively spliced isoforms, "long" and "short" (D2L and D2S), which differ by 29 amino acids in the third cytoplasmic domain. The functional differences between these two isoforms are still obscure. We have performed pulse-chase studies on the D2L and D2S receptors expressed in CHO cells in order to follow the post-translational processing of the two isoforms. Both isoforms are present in three post-translational states: a newly synthesized protein, a partially glycosylated product, and a fully glycosylated mature 70-kDa receptor. However, the processing to the mature receptor differs between the two isoforms. First, the D2S receptor is processed to the mature 70-kDa species faster than the D2L receptor. Second, at 20 degrees C the D2S isoform is fully processed to the 70-kDa species, whereas the D2L isoform persists in its partially processed 45-kDa state. Finally, a significant portion of the D2L receptor remains in its partially processed form in an intracellular compartment and does not reach the plasma membrane. These results give rise to the suggestion that the difference observed between the two alternatively spliced isoforms of the D2 receptor may lie in their post-translational processing and intracellular trafficking.
D2多巴胺受体存在两种可变剪接异构体，即“长”型和“短”型（D2L和D2S），它们在第三个胞质结构域中相差29个氨基酸。这两种异构体之间的功能差异仍不清楚。我们对CHO细胞中表达的D2L和D2S受体进行了脉冲追踪研究，以追踪这两种异构体的翻译后加工过程。两种异构体都存在于三种翻译后状态：新合成的蛋白质、部分糖基化产物和完全糖基化的成熟70 kDa受体。然而，两种异构体向成熟受体的加工过程有所不同。首先，D2S受体比D2L受体更快地加工成成熟的70 kDa形式。其次，在20℃时，D2S异构体完全加工成70 kDa形式，而D2L异构体则以其部分加工的45 kDa状态持续存在。最后，很大一部分D2L受体以其部分加工的形式保留在细胞内区室中，未到达质膜。这些结果表明，D2受体的两种可变剪接异构体之间观察到的差异可能在于它们的翻译后加工和细胞内运输。
