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== Janus Kinase 2 ==

'''Janus Kinase 2''' (pronounced: JAY-nus KAY-skin TOO), often abbreviated as '''JAK2''', is a non-receptor tyrosine kinase that plays a crucial role in signal transduction for various cytokines and growth factors.

=== Etymology ===

The term "Janus Kinase" is derived from the Roman god [[Janus]], who is often depicted with two faces, symbolizing the dual nature of this kinase. The number "2" signifies its position in the family of Janus kinases, which includes JAK1, JAK2, JAK3, and TYK2.

=== Function ===

JAK2 is involved in the signaling pathways of various [[cytokines]] and [[growth factors]], including erythropoietin and thrombopoietin. It is activated upon ligand binding to the receptor, leading to phosphorylation and activation of [[signal transducers and activators of transcription]] (STATs), which then translocate to the nucleus and regulate gene expression.

=== Clinical Significance ===

Mutations in the JAK2 gene are associated with several hematological disorders, including [[polycythemia vera]], [[essential thrombocythemia]], and [[myelofibrosis]]. The most common mutation, JAK2 V617F, results in constitutive activation of the kinase, leading to uncontrolled cell proliferation.

=== Related Terms ===

* [[Janus Kinase 1]] (JAK1)
* [[Janus Kinase 3]] (JAK3)
* [[Tyrosine Kinase 2]] (TYK2)
* [[Cytokines]]
* [[Growth Factors]]
* [[Signal Transducers and Activators of Transcription]] (STATs)
* [[Polycythemia Vera]]
* [[Essential Thrombocythemia]]
* [[Myelofibrosis]]

[[Category:Medical Dictionary]]
[[Category:Biochemistry]]
[[Category:Genetics]]
[[Category:Hematology]]

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