The document summarizes the Notch signaling pathway. It describes that Notch signaling involves communication between two neighboring cells through Notch receptors and ligands. When a ligand binds to a receptor on the neighboring cell, it leads to proteolytic cleavage and release of the Notch intracellular domain, which enters the nucleus and regulates transcription of target genes involved in cell proliferation and differentiation. The pathway plays important roles in development and diseases like cancer when dysregulated.

1. ASSIGNMENT # 03
NOTCH SIGNALLING PATHWAY
Submitted To: Dr. Jamshaid Hussain
Submitted By: Nazal Gul (SP19-BTY-007)
Date of Submission: 2nd June, 2022

2. Contents:
 Introduction to Notch Signalling
 Notch Receptors
 Ligands
 Notch Signalling Pathway
 Functions of Notch Signalling Pathway
 Notch Pathway and Diseases

3. Introduction
 Notch Signalling is an “Evolutionary Conserved Signalling Pathway”.
 Important in development and homeostasis.
 It regulates cellular proliferation, differentiation and apoptosis.
 It is unique from other signalling pathways due to its ligands.
 Signalling is restricted to neighboring cells.
 This pathway is associated with tissue growth and cancer.
 Also, it is involved in cell death and tumor suppression.

4. Discovery
 In 1914, John S. Dexter noticed the appearance of a notch in the wings of
the fruit fly Drosophila melanogaster.
 The alleles of the gene were identified in 1917 by Thomas Hunt Morgan.
 Its molecular analysis and sequencing was done in the 1980s by Spyros
Artavanis-Tsakonas and Michael W. Young.

5. Notch Receptors
 Notch Signalling is the most widely used intercellular communication pathway.
 There are 4 NOTCH Receptors found in mammals.
 These are: NOTCH1, NOTCH2, NOTCH3 AND NOTCH4.
 This receptor is a single-pass transmembrane receptor protein.
 It is a heterodimer of 2 sub-units.
 The first subunit is an extracellular segment with EGF repeats.
 The second subunit consists of;
- A short extracellular domain
- A transmembrane domain
- And an intracellular domain.

6. STRUCTURE OF NOTCH RECEPTORS
Source:
https://www.researchgate.net/publication/308993039_Targeting_Notch_as_a_Therapeutic_Ap
proach_for_Human_Malignancies

7. Notch Ligands
 Notch ligands are type I transmembrane proteins.
 The ligands of the Notch receptors are characterized into 2 families;
 1. Jagged Protein Family (includes JAG 1 and JAG 2)
 2. Delta-like Protein Family (includes DLL1, DLL3, and DLL4)
 Ligand Extracellular domains are highly conserved in evolution.
 They are essential for ligand-receptor binding to activate Notch signaling.
 Intracellular domain of Notch ligands is short, only contains 70 amino acid
residues.

8. STRUCTURE OF NOTCH LIGANDS
Source:
https://www.creativebiomart.net/resource/signal-pathway-notch-signal-pathway-387.htm

9. NOTCH SIGNALLING
 Notch Signalling Pathway involves inter-cellular signalling interactions.
 Two cells are involved: sending cell and receiving cell
 Sending has more ligands than Notch receptors.
 Receiving cell has more Notch receptors than ligands.
 The ligand-receptor crosstalk controls cell fate decisions through which neuronal,
cardiac, immune, and endocrine development are regulated.
 Binding of the Delta/Jagged ligand on one cell to the Notch receptor on another cell
results in two Proteolytic Cleavages of the receptor.
 The ADAM10 or TACE metalloprotease catalyzes the S2 cleavage.

10. Source:
https://www.creativebiomart.net/resource/signal-pathway-notch-signal-pathway-387.htm
NOTCH SIGNALLING PATHWAY

11. Continued…
 This generates a substrate for S3 cleavage by the γ-secretase complex.
 This proteolytic processing mediates release of the Notch intracellular domain
(NICD).
 NICD enters the nucleus and interacts with the DNA-binding CSL (CBF1, Su(H) and
LAG-1) protein.
 The co-activator Mastermind (Mam) and other transcription factors are recruited to
the CSL complex.
 At the same time, co-repressors (Co-R) are released.
 The co-activators carry out the transcription of target genes e:g P21, CyclinD1 and
cMYC.
 These are crucial for cell division and cell cycle progression.
 This leads to cellular proliferation.

12. Source:
https://www.creativebiomart.net/resource/signal-pathway-notch-signal-pathway-387.htm
NOTCH SIGNALLING PATHWAY

13. Functions of Notch Signal Pathway
 Neuronal function and development
 Stabilization of arterial endothelial fate and angiogenesis
 Regulation of crucial cell communication events
 Cardiac valve homeostasis
 Timely cell lineage specification of both endocrine and exocrine pancreas
 Influencing of binary fate decisions of cells that must choose between the secretory
and absorptive lineages in the gut
 Expansion of the hematopoietic stem cell compartment during bone development

14. Continued…
 T cell lineage commitment from common lymphoid precursor
 Regulation of cell-fate decision in mammary glands at several distinct development
stages
 Regulation of the mitotic/meiotic decision in the C. elegans germline

15. Notch Signal Pathway and Diseases
 The abnormality of this regulatory signalling mechanism often leads to congenital
genetic diseases.
 It has been confirmed that the mutations of related genes in the Notch signaling
pathway are associated with genetic diseases such as CADASIL, Aligile's syndrome
and hypogastric hypoplasia.
 Delta 3 gene mutations can cause autosomal recessive diseases.
 A study found that Notch signaling disorders associated with certain cardiovascular
diseases.
 Animal model experiments show that it may affect the cardiovascular system from
four aspects, including vascular remodeling, vascular stability, choice of
arteriovenous and heart development.

16. Continued…
 Recent studies have found that the cleavage of amyloid precursor protein and Notch
receptor are all dependent on γ-secretase.
 So it is speculated that Notch signaling pathway may have some connection with
the occurrence and development of Alzheimer's disease.

17. Conclusion
 Notch signal is in a complex multi-dimensional regulatory network that provides a basis
for multiple functions in development.
 For example, endocytic transport of Notch receptors and ligands plays an important role
in the activation of Notch signaling.
 Ubiquitin-mediated protein degradation is crucial for preventing the continuous
activation of Notch signaling, yet its regulatory mechanism remains to be elucidated.
 The main task of future research is to unveil the mechanisms of the complex regulatory
networks of Notch signaling.
 Also, recognizing the basis for the diversity of functions of Notch signaling that will allow
us to design more specific approaches.
 And developing treatment programs to specific pathologies resulting from aberrant Notch
signaling.

18. References
 https://www.researchgate.net/publication/308993039_Targeting_Notch_as_a_Therape
utic_Approach_for_Human_Malignancies
 https://www.sciencedirect.com/science/article/abs/pii/B9780123852335000076
 https://www.frontiersin.org/articles/10.3389/fphys.2020.00929/full
 Yamamoto S, Schulze KL, Bellen HJ. Introduction to Notch signaling. Methods Mol
Biol. 2014;1187:1-14. doi: 10.1007/978-1-4939-1139-4_1. PMID: 25053477.