Phosphorylation of glycogen synthase kinase-3beta in relation to diapause  processing in the silkworm, Bombyx mori.
Glycogen synthase kinase-3 (GSK-3) is a multifunctional protein kinase that plays important roles in regulating both glycogen synthesis and protein synthesis. In the present study, we investigated GSK-3beta phosphorylation of silkworm eggs by immunoblotting with a conserved phospho-specific antibody to GSK-3beta. Results showed that the temporal changes in GSK-3beta phosphorylation were closely related to changes in glycogen levels previously reported by other researchers. In diapause eggs, an abrupt decrease in phosphorylation of GSK-3beta was found with the onset of diapause, and phosphorylation level of GSK-3beta reached a minimum level within 1 week after oviposition. However, when diapause eggs were incubated at 25 degrees C for 15 days and then transferred to 5 degrees C, a great increase in GSK-3beta phosphorylation was observed 5 days after transfer to 5 degrees C and high levels were maintained throughout the chilling period. In both non-diapause eggs and eggs whose diapause initiation was prevented by HCl, levels of GSK-3beta phosphorylation appeared to remain relatively high for several days and then greatly decreased 2 or 3 days before hatching. Moreover, GSK-3beta phosphorylation dramatically increased when dechorionated eggs were incubated in medium. The addition of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor, U0126, did not inhibit GSK-3beta phosphorylation in dechorionated eggs, although U0126 dose-dependently inhibited ERK phosphorylation. This result showed that ERK phosphorylation is not involved in upstream signaling for GSK-3beta phosphorylation and that there may be two distinct signaling pathways involved in diapause processing in Bombyx mori eggs.
Department of Zoology, National Museum of Natural Science, Taiwan, ROC.
Ju-Ling
JL
Lin
Pei-Ling
PL
Lin
Shi-Hong
SH
Gu
D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010063:Ovum / Q000737:chemistry / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D010766:Phosphorylation; D016415:Sequence Alignment
D019476:Insect Proteins; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3