Alternative definition : KEGG: Wnt proteins are secreted morphogens that are required for basic developmental
processes, such as cell-fate specification, progenitor-cell proliferation and the
control of asymmetric cell division, in many different species and organs. There are
at least three different Wnt pathways: the canonical pathway, the planar cell polarity
(PCP) pathway and the Wnt/Ca2 pathway. In the canonical Wnt pathway, the major effect
of Wnt ligand binding to its receptor is the stabilization of cytoplasmic beta-catenin
through inhibition of the bea-catenin degradation complex. Beta-catenin is then free
to enter the nucleus and activate Wnt-regulated genes through its interaction with
TCF (T-cell factor) family transcription factors and concomitant recruitment of coactivators.
Planar cell polarity (PCP) signaling leads to the activation of the small GTPases
RHOA (RAS homologue gene-family member A) and RAC1, which activate the stress kinase
JNK (Jun N-terminal kinase) and ROCK (RHO-associated coiled-coil-containing protein
kinase 1) and leads to remodelling of the cytoskeleton and changes in cell adhesion
and motility. WNT-Ca2 signalling is mediated through G proteins and phospholipases
and leads to transient increases in cytoplasmic free calcium that subsequently activate
the kinase PKC (protein kinase C) and CAMKII (calcium calmodulin mediated kinase II)
and the phosphatase calcineurin.;