Annexin 1-dependent actions of glucocorticoids in the anterior pituitary gland: roles of the N-terminal domain and protein kinase C.
Annexin 1 (ANXA1) is an important mediator of glucocorticoid action in the neuroendocrine system. As the activity of this protein in other systems is modulated by phosphorylation of its N-terminal domain, we have explored the significance of this domain and its phosphorylation status to ANXA1 actions within the pituitary gland, using an established in vitro preparation. Two N-terminal peptides, ANXA1(Ac2-26) and ANXA1(Ac1-50), inhibited forskolin-evoked ACTH and prolactin release; however, they lacked the potency and full efficacy of the parent molecule (ANXA1(1-346)), whereas other shorter N-terminal sequences were without effect. A chimeric protein comprising ANXA1(1-44) and the C-terminal core of ANXA5 (ANXA5(20-320)) also produced a partial inhibition of peptide release. Protein kinase C (PKC) blockade (PKC(19-36)) abolished the inhibitory effects of dexamethasone on forskolin-evoked peptide release and attenuated the antisecretory actions of ANXA1(Ac2-26.) ANXA5, which sequesters PKC in other systems, produced similar effects. PKC(19-36) also blocked the dexamethasone- induced translocation of a serine phosphorylated species of ANXA1 from the cytoplasm to the outer cell surface. These results suggest that 1) the N-terminal domain plays a fundamental role in effecting the inhibitory actions of ANXA1 on pituitary peptide release; 2) PKC-dependent mechanisms are essential for both the cellular exportation and the biological activity of ANXA1; and 3) ANXA1 exported from the cells is serine phosphorylated.
Department of Neuroendocrinology, Division of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College of Science Technology and Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 ONN, UK.
Christopher
C
John
Patricia
P
Cover
Egle
E
Solito
John
J
Morris
Helen
H
Christian
Roderick
R
Flower
Julia
J
Buckingham
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017305:Annexin A1 / Q000737:chemistry / Q000494:pharmacology*; D017304:Annexin A5 / Q000494:pharmacology; D015153:Blotting, Western; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013329:Structure-Activity Relationship
D017305:Annexin A1; D017304:Annexin A5; D010446:Peptide Fragments; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D011493:Protein Kinase C