Regulatory Mechanism of Glycogen Synthase Kinase-3β (GSK-3 β) During Boophilus microplus Embryo Development
Josiana G. de Andrade1; Caroline P. de Andrade2; Itabajara Vaz Jr.2 and Carlos Logullo1
1-LQFPP-CBB-UENF, Campos dos Goytacazes, RJ, Brazil, 2-Centro de Biotecnologia- UFRGS, Porto Alegre, RS, Brazil
Glycogen synthase Kinase3 (GSK3) is a multifunctional serine/ threonine kinase found in all eukaryotes. It has been classically described as involved in the glycogen synthase phosphorylation in glycogen metabolism. GSK-3β has also been identified as a regulator in a well-established component of the Wnt signaling pathway, which is essential for setting up the entire body pattern during embryonic development in Drosophila melanogaster. It may also play important roles in protein synthesis, cell proliferation, microtubule dynamics and cell motility by phosphorylating initialization factors, components of the cell-division cycle and transcription factors. Recently it was show to be required for nuclear reformation in vitro, using ovulated Xenopus leavis egg lysates. The activity of GSK3 is dependent of insulin cascade involving a protein kinase B.
In our previous work we demonstrated that the embryogenesis of the hard tick Boophilus microplus was metabolically separated in two special phases: An initial phase, until the cellular blastoderm formation, characterized by the consumption of the maternal glycogen and a second phase characterized by an intense amino acids degradation that promotes in accumulation of glycogen and glucose in this stage. Our group identified that GSK-3 β could be detected in different stage eggs of B. microplus, and its sequence showed similarities to the enzymes already described for other models. On the other hand we demonstrated that GSK activity can be regulating the PEPCK gene expression during tick embryogenesis. In the present study, we investigated the possible regulatory mechanism (s) of GSK-3β during tick embryo development. The enzyme was detected in isolated nuclear fraction by western-blot analysis, using Anti-GSK-3β antibodies. The enzyme activity was detected by radiochemically method during embryogenesis in both nuclear fractions and egg homogenates. The glycogen contents in the eggs and nuclear fractions modified according the GSK-3β activity.
Taken together our results suggest a correlation between GSK-3β activity and glycogen levels during B. microplus embryo development.
Supported by: PRONEX, FAPERJ, CAPES and CNPq
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