CST Guide:

Section I: Research Areas
chapter 06: Development and differentiation
Wnt/b-Catenin Signaling
Notch Signaling
OFF-State
Cadherin
β-catenin
α-catenin
p120
DKKs
LRP5/6
SFRP
Frizzled
ON-State
Porc WIF
WLS
SFRP
Wnt
LRP5/6
CK1 GSK-3
Axin
Frizzled
Dvl
Naked
R-spondins
LGR5/6
RNF43
ZNRF3
Signal
Sending
Cell
Inactive
Ligand
Delta
Jagged
Active
Ligand
Neur
or Mib
ub
ub
Delta
Jagged
Endosome
ub
Ligand
Repositioning
Epsin
ub
Ligand-receptor
Internalization
Skp
Proteasomal
Degradation
β-TrCP
ub β-catenin
Tankyrase
PP2A
Axin
APC GSK-3
WTX
β-catenin
CK1
CYLD
β-catenin
Rac1
ub
Dvl
PAR-1
ub TAB2
TAK1
TAB1
NLK
Extracellular
Space
Signal
Receiving
Cell
Notch
Fringe
Deltex
NEDD4
Golgi
ub
Notch
Recycling
Activated
Receptor
Endosome
NUMB
α-Adaptin
ADAM/
TACE
S2 Cleavage
TM
NICD
S3 Cleavage
FBX7
Nicastrin
Presenilin
APH-1
PEN-2
γ-Secretase
Complex
Ubiquitin
Degradation
Cytoplasm
Nucleus
OFF
HDAC
Groucho
TCF3
HDAC
Groucho β-catenin
Hesx1
FoxO
Pygo BCL9
Brg1
β-catenin
CBP
LEF1/TCF1
FoxO
ICAT
β-catenin
Chibby
NLK
TAZ
Target Genes:
Myc, Cyclin D1,
TCF-1, PPAR-δ,
MMP-7, Axin-2,
CD44, etc.
Pit1
Snail1
Migration
Adhesion
S1 Cleavage Furin
ER
Cytoplasm
Nucleus
O-Fut
CtBP1 CIR HDAC
KDM5A
SMRT SHARP
CSL SKIP
Inactive
Lysosomal
Degradation
KDM5A
HAT
MAML
SKIP
CSL
Active
Notch Target Genes
HES Family
Myc
p21
Cyclin D3
The conserved Wnt/β-Catenin pathway regulates stem cell pluripotency and cell fate decisions during development. This developmental cascade integrates signals from other
pathways, including retinoic acid, FGF, TGF-β, and BMP, within different cell types and tissues. The Wnt ligand is a secreted glycoprotein that binds to Frizzled receptors, leading
to the formation of a larger cell surface complex with LRP5/6. Frizzleds are ubiquitinated by ZNRF3 and RNF43, whose activity is inhibited by R-spondin binding to LGR5/6.
In this manner R-spondins increase sensitivity of cells to the Wnt ligand. Activation of the Wnt receptor complex triggers displacement of the multifunctional kinase GSK-3β
from a regulatory APC/Axin/GSK-3β-complex. In the absence of Wnt-signal (Off-state), β-catenin, an integral E-cadherin cell-cell adhesion adaptor protein and transcriptional
co-regulator, is targeted by coordinated phosphorylation by CK1 and the APC/Axin/GSK-3β-complex leading to its ubiquitination and proteasomal degradation through the
β-TrCP/Skp pathway. In the presence of Wnt ligand (On-state), the co-receptor LRP5/6 is brought in complex with Wnt-bound Frizzled. This leads to activation of Dishevelled
(Dvl) by sequential phosphorylation, poly-ubiquitination, and polymerization, which displaces GSK-3β from APC/Axin through an unclear mechanism that may involve substrate
trapping and/ or endosome sequestration. Stablized β-catenin is translocated to the nucleus via Rac1 and other factors, where it binds to LEF/TCF transcription factors, displacing
co-repressors and recruiting additional co-activators to Wnt target genes. Additionally, β-catenin cooperates with several other transcription factors to regulate specific
targets. Importantly, researchers have found β-catenin point mutations in human tumors that prevent GSK-3β phosphorylation and thus lead to its aberrant accumulation.
E-cadherin, APC, R-spondin and Axin mutations have also been documented in tumor samples, underscoring the deregulation of this pathway in cancer. Wnt signaling has
also been shown to promote nuclear accumulation of other transcriptional regulator implicated in cancer, such as TAZ and Snail1. Furthermore, GSK-3β is involved in glycogen
metabolism and other signaling pathways, which has made its inhibition relevant to diabetes and neurodegenerative disorders.
Select Reviews:
Angers, S. and Moon, R.T. (2009) Nat. Rev. Mol. Cell Biol. 10, 468–477. • Cadigan, K.M. and Waterman, M.L. (2012) Cold Spring Harb. Perspect. Biol. 4, a007906. •
Clevers, H. and Nusse, R. (2012) Cell 149, 1192–1205. • de Lau, W., Peng, W.C., Gros, P. and Clevers, H. (2014) Genes Dev. 28, 305–316. • Fearon, E.R. (2009) Cancer
Cell 16, 366–368. • MacDonald, B.T., Tamai, K. and He, X. (2009) Dev. Cell 17, 9–26. • Metcalfe, C. and Bienz, M. (2011) J. Cell. Sci. 124, 3537–3544. • Niehrs, C.
(2012) Nat. Rev. Mol. Cell Biol. 13, 767–779. • Nusse, R. (2010) The Wnt Homepage. • Petersen, C.P. and Reddien, P.W. (2009) Cell 139, 1056–1068. • Sokol, S.Y.
(2011) Development 138, 4341–4350. • van Amerongen, R. and Nusse, R. (2009) Development 136, 3205–3214. • Valenta, T., Hausmann, G., and Basler, K. (2012)
EMBO J. 31, 2714–2736.
© 2003–2015 Cell Signaling Technology, Inc. • We would like to thank Prof. Kenneth Cadigan, University of Michigan, Ann Arbor, MI, for reviewing this diagram.
160 For Research Use Only. Not For Use in Diagnostic Procedures. See pages 302 & 303 for Pathway Diagrams, Application, and Reactivity keys.
Notch signaling is an evolutionarily conserved pathway in multicellular organisms that regulates cell-fate determination during development and maintains adult tissue homeostasis.
The Notch pathway mediates juxtacrine cellular signaling wherein both the signal sending and receiving cells are affected through ligand-receptor crosstalk by which
an array of cell fate decisions in neuronal, cardiac, immune, and endocrine development are regulated. Notch receptors are single-pass transmembrane proteins composed
of functional extracellular (NECD), transmembrane (TM), and intracellular (NICD) domains. Notch receptors are processed in the ER and Golgi within the signal-receiving cell
through cleavage and glycosylation, generating a Ca 2+ -stabilized heterodimer composed of NECD noncovalently attached to the TM-NICD inserted in the membrane (S1
cleavage). The processed receptor is then endosome-transported to the plasma membrane to enable ligand binding in a manner regulated by Deltex and inhibited by NUMB.
In mammalian signal-sending cells, members of the Delta-like (DLL1, DLL3, DLL4) and the Jagged (JAG1, JAG2) families serve as ligands for Notch signaling receptors.
Upon ligand binding, the NECD is cleaved away (S2 cleavage) from the TM-NICD domain by TACE (TNF-α ADAM metalloprotease converting enzyme). The NECD remains
bound to the ligand and this complex undergoes endocytosis/recycling within the signal-sending cell in a manner dependent on ubiquitination by Mib. In the signal-receiving
cell, γ-secretase (also involved in Alzheimer’s disease) releases the NICD from the TM (S3 cleavage), which allows for nuclear translocation where it associates with the CSL
(CBF1/Su(H)/Lag-1) transcription factor complex, resulting in subsequent activation of the canonical Notch target genes: Myc, p21, and the HES-family members. The Notch
signaling pathway has spurred interest for pharmacological intervention due to its connection to human disease. Importantly, researchers have found Notch receptor activating
mutations leading to nuclear accumulation of NICD are common in adult T cell acute lymphoblastic leukemia and lymphoma. In addition, loss-of-function Notch receptor and
ligand mutations are implicated in several disorders, including Alagille syndrome and CADASIL, an autosomal dominant form of cerebral arteriopathy.
Select Reviews:
Ables, J.L., Breunig, J.J., Eisch, A.J., Rakic, P. (2011) Nat. Rev. Neurosci. 12, 269–283. • Andersson, E.R., Lendahl, U. (2014) Nat. Rev. Drug Discov. 13, 357–378. • Aster,
J.C., Blacklow, S.C., Pear, W.S. (2011) J. Pathol. 223, 262–273. • Bai, G., Pfaff, S.L. (2011) Neuron 72, 9–21. • de la Pompa, J.L., Epstein, J.A. (2012) Dev. Cell 22, 244–
254. • Ntziachristos, P., Lim, J.S., Sage, J., Aifantis, I. (2014) Cancer Cell. 24. • Ranganathan, P., Weaver, K.L., Capobianco, A.J. (2011) Nat. Rev. Cancer 11, 338–351.
• Weinmaster, G., Fischer, J.A. (2011) Dev. Cell 21, 134–144. • Yuan, J.S., Kousis, P.C., Suliman, S., Visan, I., Guidos, C.J. (2010) Annu. Rev. Immunol. 28, 343–365.
© 2006–2015 Cell Signaling Technology, Inc. • We would like to thank Dr. Hans Widlund, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, for reviewing this diagram.
www.cellsignal.com/cstpathways 161