|
||
J. Cell Biol.,
Volume 145, Number 4, May 17, 1999 741-756



* Division of Cell Biology, Max-Planck Institute for Developmental Biology, 72076 Tübingen, Germany; and Axin was identified as a regulator of embryonic axis induction in vertebrates that inhibits the Wnt
signal transduction pathway. Epistasis experiments in
frog embryos indicated that Axin functioned downstream of glycogen synthase kinase 3
Department of
Genetics and Development, College of Physicians and Surgeons, Columbia University, New York 10032
(GSK3
) and
upstream of
-catenin, and subsequent studies showed
that Axin is part of a complex including these two proteins and adenomatous polyposis coli (APC). Here, we
examine the role of different Axin domains in the effects on axis formation and
-catenin levels. We find that the regulators of G-protein signaling domain (major APC-binding site) and GSK3
-binding site are required, whereas the COOH-terminal sequences, including a protein phosphatase 2A binding site and the DIX
domain, are not essential. Some forms of Axin lacking the
-catenin binding site can still interact indirectly
with
-catenin and regulate
-catenin levels and axis
formation. Thus in normal embryonic cells, interaction
with APC and GSK3
is critical for the ability of Axin
to regulate signaling via
-catenin. Myc-tagged Axin is
localized in a characteristic pattern of intracellular spots as well as at the plasma membrane. NH2-terminal
sequences were required for targeting to either of these
sites, whereas COOH-terminal sequences increased localization at the spots. Coexpression of hemagglutinin-tagged Dishevelled (Dsh) revealed strong colocalization with Axin, suggesting that Dsh can interact with
the Axin/APC/GSK3/
-catenin complex, and may thus
modulate its activity.
-catenin;
glycogen synthase kinase 3
(GSK3
);
adenomatous polyposis coli (APC);
Dishevelled (Dsh);
dorsal axis formation
This article has been cited by other articles:
|
|