Editing Signal transduction (section)

==Major pathways==
{{Further|List of signalling pathways}}

[[File:How to read signal transduction diagrams.png|thumb|How to read signal transduction diagrams, what does normal arrow and flathead arrow means.]]
[[File:Elements of Signal transduction cascade networking.png|thumb|Elements of Signal transduction cascade networking]]

Following are some major signaling pathways, demonstrating how ligands binding to their receptors can affect second messengers and eventually result in altered cellular responses.
* [[MAPK/ERK pathway]]: A pathway that couples intracellular responses to  the binding of [[growth factor]]s to [[cell (biology)|cell]] surface [[Receptor (biochemistry)|receptor]]s.&nbsp;  This pathway is very complex and includes many [[protein]] components.<ref name="Orton2005">{{Cite journal |vauthors=Orton RJ, Sturm OE, Vyshemirsky V, Calder M, Gilbert DR, Kolch W |date=December 2005 |title=Computational modelling of the receptor-tyrosine-kinase-activated MAPK pathway |journal=The Biochemical Journal |volume=392 |issue=Pt 2 |pages=249–61 |doi=10.1042/BJ20050908 |pmc=1316260 |pmid=16293107}}</ref>&nbsp;  In many cell types, activation of this pathway promotes [[cell division]], and many forms of [[cancer]] are associated with aberrations in it.<ref>{{Cite journal |vauthors=Vogelstein B, Kinzler KW |date=August 2004 |title=Cancer genes and the pathways they control |journal=Nature Medicine |volume=10 |issue=8 |pages=789–99 |doi=10.1038/nm1087 |pmid=15286780 |s2cid=205383514}}</ref>
* [[cAMP-dependent pathway]]: In humans, cAMP works by activating protein kinase A (PKA, [[cAMP-dependent protein kinase]]) (see picture), and, thus, further effects depend mainly on [[function of cAMP-dependent protein kinase|cAMP-dependent protein kinase]], which vary based on the type of cell.
* [[IP3/DAG pathway|IP<sub>3</sub>/DAG pathway]]: PLC cleaves the [[phospholipid]] [[phosphatidylinositol 4,5-bisphosphate]] (PIP2), yielding [[diacyl glycerol]] (DAG) and [[inositol 1,4,5-triphosphate]] (IP<sub>3</sub>).&nbsp;  DAG remains bound to the membrane, and IP<sub>3</sub> is released as a soluble structure into the [[cytosol]].&nbsp;  IP<sub>3</sub> then diffuses through the cytosol to bind to [[Inositol triphosphate receptor|IP<sub>3</sub> receptors]], particular [[calcium channel]]s in the [[endoplasmic reticulum]] (ER).&nbsp;  These channels are specific to [[calcium]] and allow the passage of only calcium to move through.&nbsp;  This causes the cytosolic concentration of Calcium to increase, causing a cascade of intracellular changes and activity.<ref name=alberts/>&nbsp;  In addition, calcium and DAG together works to activate PKC, which goes on to phosphorylate other molecules, leading to altered cellular activity.&nbsp;  End-effects include taste, manic depression, tumor promotion, etc.<ref name="alberts">{{Cite book |url=https://archive.org/details/molecularbiolog000wils |title=Molecular biology of the cell |vauthors=Alberts B, Lewis J, Raff M, Roberts K, Walter P |publisher=Garland Science |year=2002 |isbn=978-0-8153-3218-3 |edition=4th |location=New York |url-access=registration}}</ref>