Effect of glucocorticoid on the biosynthesis of growth hormone-containing secretory granules in pituitary cells.
Recent studies have suggested that treatment of glucocorticoid to immature growth hormone (GH)-producing cell line, MtT/S cells, dramatically induced the accumulation of GH-containing secretory granules in the cytosol and differentiated into mature GH-producing cells. However, the molecular mechanism of glucocorticoid-induced GH-containing secretory granule biogenesis in the MtT/S cells remains unknown. In the present study, we found that GH mRNA expression was facilitated by application of glucocorticoid. We artificially increased GH synthesis by transfection of green fluorescent protein-tagged GH (GH-GFP) gene. We found that the artificial elevation of GH expression in the cells did not accumulate the secretory granules in the cytosol, whereas glucocorticoid-induced the biogenesis of granules in GH-GFP-expressing MtT/S cells. We next performed DNA microarray and real-time RT-PCR analysis and found that glucocorticoid significantly altered the expression of membrane trafficking-related protein, syntaxin11 (Syx11). Immunocytochemical analysis further demonstrated that Syx11 positive structures were well colocalized with GH-containing granules in both MtT/S cells and rat anterior pituitary gland. Our findings indicate that glucocorticoid regulate the expression of Syx11 and facilitate the biogenesis and the trafficking of GH-containing granules in the MtT/S cells.
Kawashima
Risa
R
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.
Ikematsu
Kazuya
K
Abe
Yuki
Y
Sato
Mai
M
Tsuruya
Shinichiro
S
Nakasono
Ichiro
I
Fukushima
Hiroyuki
H
Inoue
Kinji
K
Tsuboi
Takashi
T
D000818:Animals; D002460:Cell Line; D005938:Glucocorticoids / Q000494:pharmacology*; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D013006:Growth Hormone / Q000096:biosynthesis* / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022142:Secretory Vesicles / Q000378:metabolism*
D005938:Glucocorticoids; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins; D013006:Growth Hormone