Editing Kinase (section)

===Mitogen-activated protein kinases===
{{main|Mitogen-activated protein kinase}}

[[Mitogen-activated protein kinase|MAP kinases]] (MAPKs) are a family of serine/threonine kinases that respond to a variety of extracellular growth signals. For example, growth hormone, epidermal growth factor, platelet-derived growth factor, and insulin are all considered mitogenic stimuli that can engage the MAPK pathway. Activation of this pathway at the level of the receptor initiates a signaling cascade whereby the [[Ras subfamily|Ras GTPase]] exchanges [[Guanosine diphosphate|GDP]] for [[Guanosine triphosphate|GTP]]. Next, Ras activates [[Raf kinase]] (also known as MAPKKK), which activates [[Mitogen-activated protein kinase kinase|MEK]] (MAPKK). MEK activates [[Mitogen-activated protein kinase|MAPK]] (also known as ERK), which can go on to regulate [[transcription (genetics)|transcription]] and [[translation (biology)|translation]]. Whereas RAF and MAPK are both serine/threonine kinases, MAPKK is a tyrosine/threonine kinase.

[[File:Components of the MAPK Pathway.png|thumb|upright=2|A variety of mitogenic signals engage the MAPK pathway and promote cell growth and differentiation through a kinase cascade.]]

MAPK can regulate transcription factors directly or indirectly. Its major transcriptional targets include ATF-2, Chop, c-Jun, c-Myc, DPC4, Elk-1, Ets1, Max, MEF2C, NFAT4, Sap1a, STATs, Tal, p53, CREB, and Myc. MAPK can also regulate translation by phosphorylating the S6 kinase in the large ribosomal subunit. It can also phosphorylate components in the upstream portion of the MAPK signalling cascade including Ras, Sos, and the [[EGF receptor]] itself.<ref name=MAPK>{{cite journal | vauthors = Garrington TP, Johnson GL | title = Organization and regulation of mitogen-activated protein kinase signaling pathways | journal = Current Opinion in Cell Biology | volume = 11 | issue = 2 | pages = 211–218 | date = April 1999 | pmid = 10209154 | doi = 10.1016/s0955-0674(99)80028-3 }}</ref>

The carcinogenic potential of the MAPK pathway makes it clinically significant. It is implicated in cell processes that can lead to uncontrolled growth and subsequent tumor formation. Mutations within this pathway alter its regulatory effects on [[cell differentiation]], proliferation, survival, and [[apoptosis]], all of which are implicated in various forms of [[cancer]].<ref name=MAPK />