Externalization of annexin I from a folliculo-stellate-like cell line.
Our recent studies on rat pituitary tissue suggest that the annexin I-dependent inhibitory actions of glucocorticoids may not be exerted directly on endocrine cells but indirectly via folliculo-stellate (FS) cells. FS cells contain glucocorticoid receptors and abundant annexin I. We have studied the localization of annexin I in FS cells and the ability of dexamethasone to induce annexin I secretion by an FS (TtT/GF) cell line, using Western blotting and immunofluorescence microscopy. Exposure of TtT/GF cells to dexamethasone (0.1 micro M, 3 h) caused an increase in the amount of annexin I protein in the intracellular compartment and attached to the surface of the cells. In nonpermeabilized cells, immunofluorescence labeling revealed that annexin I immunoreactivity was associated with the cell surface and concentrated in focal patches on the ends of cytoplasmic processes; dexamethasone (0.1 micro M, 3 h) increased both the number and intensity of these foci. Immunogold electron microscopy confirmed in anterior pituitary tissue the presence of immunoreactive-annexin at the surface of FS cell processes contacting endocrine cells. These data support our hypothesis that annexin I is released by FS cells in response to glucocorticoids to mediate glucocorticoid inhibitory actions on pituitary hormone release via a juxtacrine mechanism.
Chapman
Lee
L
Department of Human Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, United Kingdom.
Nishimura
Aya
A
Buckingham
Julia C
JC
Morris
John F
JF
Christian
Helen C
HC
D000818:Animals; D017305:Annexin A1 / Q000032:analysis / Q000378:metabolism*; D015153:Blotting, Western; D002450:Cell Communication; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005938:Glucocorticoids / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010903:Pituitary Gland, Anterior / Q000648:ultrastructure
D017305:Annexin A1; D005938:Glucocorticoids; D003907:Dexamethasone