Protein Links and Information
How does the JAK3 protein actually function?
The JAK3 protein functions as an intermediate in a pathway with STATs (signal transducers and activators of transcription). As the first step in the pathway cytokines from outside the cell bind to type I and II cytokine receptors in the membranes of immune cells. The FERM domain of the JAK3 protein then associates with the common gamma subunit of the cytokine receptor; the JAK1 protein binds to another portion of the receptor. The JAKs work together to phosphorylate tyrosine residues on the receptor which then bind to the SH2 domains of (specific) STAT molecules. The JAK molecules then phosphorylate the STAT molecules, which dimerize and move to the nucleus of the cell and upregulate transcription of specific sequences. [2]
Figure 1: The JAK/STAT pathway [1]
Nonspecific JAK-STAT pathway video
The video below [3] shows a general JAK-STAT pathway as described above. A description of what is happening at each point appears at the top of the video but it goes fast, so If you plan on reading the text you may want to consider pausing the video at each step.
References
[1] Figure 1: http://en.wikipedia.org/wiki/File:Jakstat_pathway.svg
[2] Notarangelo, L.D., Mella, P., Jones, A., de Saint Basile, G., Savoldi, G., Cranston, T., Vihinen, M., Schumacher, R.F. (2001). Mutations in severe combined immune deficiency (SCID) due to JAK3 deficiency. Human Mutation, 18(4):255-63. doi: 10.1002/humu.1188
[3] Cytokine Signaling by the JAK STAT Pathway: http://www.youtube.com/watch?v=G4K6IQZGHJc
