Immunocytochemical evidence for intragranular processing of pro-opiomelanocortin in the melanotropic cells of the rabbit |
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Authors: | Dr M E Stoeckel S Schimchowitsch J C Garaud G Schmitt H Vaudry M J Klein A Porte |
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Institution: | (1) Laboratoire de Physiologie Générale, Université Louis Pasteur, U.A. CNRS n , 309 Strasbourg;(2) INSERM Unité 61, Strasbourg;(3) Groupe de Recherche d'Endocrinologie moléculaire, ERA 89 CNRS, Mont Saint-Aignan, France;(4) Laboratoire de Physiologie Générale, 21, rue René Descartes, F-67084 Strasbourg Cedex, France |
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Abstract: | Summary The immunogold technique, employing antisera with clear-cut specificities, was used to localise different processing stages of pro-opiomelanocortin (POMC) in rabbit melanotropic cells. While the antiserum against
3-MSH labelled all the secretory granules including intrasaccular condensations in the Golgi apparatus, antisera against -MSH only labelled extra-Golgi secretory vesicles (SV). All extra-Golgi SV were likewise labelled with the three antisera against -MSH used, despite their different specificities for the desacetylated, N-acetylated or C-amidated forms of the peptide. The antibody against -endorphin also labelled the extra-Golgi SV, while only some SV were labelled with the antibody against -endorphin. These results correlate with biochemical data in favour of mainly — if not exclusively — intragranular processing of POMC. Except for 3-MSH, the cleavage of which could coincide with Golgi packaging of secretory material, other post-translational modifications of the precursor seem to occur when SV are discharged outside the Golgi area. The cleavage of -endorphin appears to be a later step in POMC processing, occurring in some mature SV. |
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Keywords: | Melanotrophs Immunogold technique Secretory vesicles 3-MSH" target="_blank">gif" alt="gamma" align="MIDDLE" BORDER="0">3-MSH -MSH" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">-MSH Endorphins Rabbit |
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