Annexin A1 (ANXA1) has an important role in cell-cell communication in the host defense and neuroendocrine systems. In both systems, its actions are exerted extracellularly via membrane-bound receptors on adjacent sites after translocation of the protein from the cytoplasm to the cell surface of adjacent cells. This study used molecular, microscopic, and pharmacological approaches to explore the mechanisms underlying the cellular exportation of ANXA1 in TtT/GF (pituitary folliculo-stellate) cells. LPS caused serine-phosphorylation of ANXA1 (ANXA1-S 27 -PO 4 ) and translocation of the phosphorylated protein to the cell membrane. The fundamental requirement of phosphorylation for membrane translocation was confirmed by immunofluorescence microscopy on cells transfected with wild-type or mutated (S 27 /A) ANXA1 constructs tagged with enhanced green fluorescence protein.The trafficking of ANXA1-S 27 -PO 4 to the cell surface was dependent on PI3-kinase and MAPkinase. It also required HMG-coenzyme A and myristoylation. The effects of HMG-coenzyme A blockade were overcome by mevalonic acid (the product of HMG-coenzyme A) and farnesylpyrophosphate but not by geranyl-geranylpyrophosphate or cholesterol. Together, these results suggest that serine-27 phosphorylation is essential for the translocation of ANXA1 across the cell membrane and also identify a role for isoprenyl lipids. Such lipids could target consensus sequences in ANXA1. Alternatively, they may target other proteins in the signal transduction cascade (e.g., transporters). Keywordsphosphorylation; green fluorescence protein; lipidation; signaling Annexin A1 (ANXA1) is a Ca 2+ -and phospholipids-binding protein that acts both intracellularly and extracellularly to modulate cell signaling. Data from our laboratory have shown that it has a particularly important role in the regulation of the host defense and neuroendocrine systems and that ANXA1 mimetics may provide a novel therapeutic approach to the control of inflammatory disease (reviewed in ref 1). The regulatory actions of ANXA1 in both systems appear to be exerted mainly extracellularly, via membrane-bound cell surface receptors (2-4). Access of endogenous ANXA1 to these receptors is thus dependent on the translocation of the protein from its cytoplasmic stores to the cell surface (1). These conclusions are supported by evidence that within the neuroendocrine system ANXA1 is expressed in cells adjacent to its target cells (5), and it is concentrated at sites where the cells make contact with UKPMC Funders Group Author ManuscriptUKPMC Funders Group Author Manuscript endocrine cells (6) and translocated to the cell surface in response to appropriate stimuli (7,8). Further evidence of the paracrine/juxtacrine mode of ANXA1 action is provided by evidence that drugs that prevent the cellular exportation of the protein ablate the regulatory actions of endogenous ANXA1 within the neuroendocrine system (6,7,9,10) as also do compounds that destroy the cell surface ANXA1 receptors (2). Substantial evidence...

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The incidence of ischemia induced by carotid occlusion decreased from 44% to 26% in PCPA-treated animals, which also suggests that depletion of 5-HT available for neuronal release prior to the induction of ischemia may reduce stroke incidence by limiting impairment of collateral vasocapacitance. PCPA pretreatment did not influence the development of edema in the occluded hemisphere of ischemic animals once ischemia was established.

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The effects of selective agonists and antagonists of type 1 (V1) and type 2 (V2) vasopressin receptors on the secretion of ACTH in vitro by segments of adenohypophysial tissue and in vivo in rats pretreated with pentobarbitone and chlorpromazine were studied in the presence and absence of the 41 amino acid-containing peptide, corticotrophin-releasing factor-41 (CRF-41). The non-selective vasopressin receptor agonist, arginine vasopressin (AVP) and the V1-receptor agonist, felypressin caused dose-related increases in ACTH release in vivo and in vitro but the V2-receptor agonist, desmopressin was only weakly active in this respect. Their actions in vitro were antagonized competitively by the V1-receptor antagonist, d(C2H5)2-AVP, but were unaffected by the V2-receptor antagonist, d(CH2)5-D-Iso2-Thr4-AVP. Arginine vasopressin, felypressin and desmopressins in concentrations considerably lower than those necessary to elicit directly the release of ACTH, potentiated, in a dose-related manner, the activity of CRF-41 in vitro. The potentiating effects were not antagonized by the V2-receptor antagonist or by low concentrations of the V1-receptor antagonist. At a higher concentration, the V1-receptor antagonist reduced, but did not abolish, the potentiating effects of AVP and its analogues. However, at this concentration, it also exhibited weak intrinsic activity and, like the agonists, potentiated the response to CRF-41. The results suggest that the direct effect of AVP on ACTH release is mediated by V1-like receptors. The vasopressin receptors involved in the potentiation of CRF-41 activity appear to be different.