Enzymatic cleavage of pro‐opiomelanocortin by anterior pituitary granules

Seidah, Nabil G.; Pélaprat, Didier; Lazure, Claude; Chrétien, Michel

doi:10.1016/0014-5793(83)80418-9

Cited by 14 publications

(1 citation statement)

References 29 publications

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“…Many data now indicate that processing of prohormones to polypeptide hormones takes place in the secretion granules of endocrine cells and neurons, and both serine and thiol proteases, among other enzymes, have been implicated in the posttranslational proteolysis (38)(39)(40)(41)(42). It has previously been proposed that plasminogen activators play a role in these processes (22)(23)(24).…”

Section: Discussionmentioning

confidence: 99%

Immunocytochemical demonstration of tissue-type plasminogen activator in endocrine cells of the rat pituitary gland.

Kristensen¹,

Nielsen²,

Grøndahl-Hansen³

et al. 1985

The Journal of Cell Biology

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We immunocytochemically stained rat pituitary glands using antibodies against plasminogen activators of the tissue type (t-PA) and the urokinase type (u-PA). A large population of endocrine cells in the anterior lobe of the gland displayed intense cytoplasmic immunoreactivity with anti-t-PA. In some areas of the intermediate lobe we found a weak staining, and we observed weakly staining granular structures in the posterior lobe. Controls included absorption of the antibodies with highly purified t-PA. In addition, SDS PAGE followed by immunoblotting of pituitary gland extracts revealed only one band with an electrophoretic mobility similar to that of t-PA when stained with anti-t-PA IgG. No u-PA immunoreactivity was detected in the rat pituitary gland. Sequential staining experiments using antibodies against growth hormone and t-PA demonstrated that the t-PA-immunoreactive cells constitute a large subpopulation of the growth hormone-containing cells. These findings represent the first direct evidence for the presence of t-PA in cell types other than endothelial cells in the intact normal organism. In this article we discuss the implications of the results for a possible role of t-PA in the posttranslational processing of prohormones.Plasminogen activators are serine proteases, able to convert the proenzyme plasminogen into the active protease plasmin. It is well documented that there are at least two types of mammalian plasminogen activators. The two types that can be distinguished by differences in molecular weight (Mr) and immunological reactivity (for reviews see references 1-4) are products of different genes (5-8). Both the urokinase-type plasminogen activator (u-PA), ~ Mr ~ 50,000, and the tissuetype plasminogen activator (t-PA), Mr ~ 70,000, are secreted from cells in culture as partly or completely inactive proenzymes (9-12), and it is generally believed that they exert their biological functions by activation of extracellular plasminogen.Production and release ofplasminogen activators have been implicated in thrombolysis (for reviews see references 2 and 3) and a variety of biological processes involving tissue degradation (for reviews see references 4 and 13), for example Abbreviations used in this paper. TBS, 0.05 M Tris-HC1, pH 7.4, containing 0.15 M NaCl; t-PA, tissue-type plasminogen activator; u-PA, urokinase-type plasminogen activator.

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