ISSN:
1365-2826
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Prolactin cells derived from the anterior pituitaries of female rats were cultured in the presence of tunicamycin, swainsonine, castanospermine, β-hydroxynorvaline and monensin in order to study their effect on the post-translational processing of the Mr 17,000, 23,000 and 26,000 prolactin molecular forms. Sodium-dodecyl-sulphate polyacrylamide electrophoresis and subsequent immunoblotting revealed that: 1) tunicamycin, swainsonine and castanospermine, compounds that are essentially known as inhibitors of the N-glycosylation processus, had no effect on Mr 17,000, 23,000 and 26,000 rat prolactin; 2) βhydroxynorvaline, which has been assumed to inhibit processing of pre-prolactin to mature 23,000 prolactin, did not increase the synthesis of 26,000 rat prolactin. In case of inhibition of the processing of a pre-prolactin to mature prolactin, one would expect an increase of the pre-prolactin; consequently, we could not establish the 26,000 rat prolactin, we revealed in immunoblotting, as a pre-prolactin; 3) monensin affected the post-translational processing of 17,000 and 26,000 rat prolactin, but left the 23,000 mature form intact. This is an important finding for the following reasons: monensin blocks the transport of secretory and membrane proteins, and this blockade prevents the cleavage of these molecules; indeed, production of 17,000 rat prolactin, a form of cleaved prolactin, was inhibited. Monensin also affects glycosylation and 26,000 rat prolactin has been identified as a presumably O-iinked glycosylated variant. The fact that its synthesis is inhibited by monensin treatment, but not by inhibitors of the N-linked process, particularly tunicamycin, and that 26,000 rat prolactin is susceptible to mild alkali and decomposition via β-elimination are decisive arguments in favour of the O-linked glycosidic linkage.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2826.1989.tb00142.x
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