Role of glycogen synthase kinase 3 beta as a negative regulator of dorsoventral axis formation in Xenopus embryos.

Abstract

The dorsoventral axis is established early in Xenopus development and may involve signaling by Wnts, a family of Wntl-protooncogene-related proteins. The protein kinase shaggy functions in the wingless/Wnt signaling pathway, which operates during Drosophila development. To assess the role of a closely related kinase, glycogen synthase kinase 3,B , in vertebrate embryogenesis, we cloned a cDNA encoding a Xenopus homolog of To assess a possible role for GSK-3,B in dorsoventral axis formation, we cloned a Xenopus homolog of GSK-3,B/shaggy (XGSK-313)t and examined its expression pattern in early embryos. We also constructed several mutated forms of rat GSK-3,3 and studied effects of their overexpression in Xenopus embryos. Since shaggy is a presumed negative regulator of the Wg pathway in Drosophila, we speculated that a dominant negative mutant of GSK-3P may mimic the effect of ectopic Wnt expression on embryonic axis formation. Consistent with these expectations, microinjection of an enzymatically inactive form of rat GSK-3f3 carrying a point mutation in the ATPbinding site triggered an ectopic body axis formation in early embryos. This effect could be suppressed by the wild-type XGSK-3,3. Our data strongly indicate that the endogenous

Gastrin stabilises β-catenin protein in mouse colorectal cancer cells

“…Inhibition of CK2 activity did not abolish gastrin-mediated effects on b-catenin, suggesting that gastrin signalling possesses both CK2-dependent and -independent properties. It is plausible that this important regulatory peptide controls b-catenin through multiple regulators, as b-catenin itself is known to have numerous modulators (Dominguez et al, 1995;Yost et al, 1996;Korinek et al, 1997;Ikeda et al, 1998;Kishida et al, 1998;Li et al, 1999;Farr et al, 2000;Song et al, 2000Song et al, , 2003a.…”

“…Under normal conditions, b-catenin degradation ensures tightly regulated cytoplasmic levels of this protein. Adenomatous polyposis coli appears to regulate the degradation of b-catenin protein by recruiting b-catenin into the negative regulatory complex for phosphorylation by glycogen synthase kinase 3b (GSK3b) in the Nterminus (Dominguez et al, 1995;Yost et al, 1996;Korinek et al, 1997) and subsequent proteasomal degradation (Aberle et al, 1997). Intricate interactions among other b-catenin binding partners also serve to facilitate the degradation of b-catenin to maintain a delicate balance Kishida et al, 1998;Li et al, 1999;Farr et al, 2000).…”

SLC26 anion exchangers of guinea pig pancreatic duct: molecular cloning and functional characterization

“…Full-length cDNAs were cloned into PCR-cloning vector pCRII (Invitrogen), and plasmid cDNA inserts were sequenced in entirety to ensure absence of PCR-introduced mutations, then subcloned into oocyte expression vector pXT7 (13,50) and mammalian expression vector pcDNA3 (Invitrogen). For immunodetection at the oocyte surface, each cDNA in pXT7 was also hemagglutinin (HA)-tagged at its NH 2-terminus through flexible linker sequence GASG.…”

Purification and molecular cloning of a secreted, Frizzled-related antagonist of Wnt action

“…The Wnt signaling pathway is thought to proceed through suppression of the activity of glycogen synthase kinase-3, a cytoplasmic serine-threonine kinase (13). Axis duplication induced by a dominant-negative, kinase-inactive mutant of glycogen synthase kinase-3␤ (33,45,46) was not affected by FRP (data not shown), consistent with the assumption that FRP directly interferes with Wnt signaling at the cell surface, not by indirectly interfering with a late step in the Wnt signaling pathway.…”