Figure 2.

Signal transduction pathways of cytokine receptors (A) and the JAK-STAT pathway (B). (A) JAKs non-covalently associate with cytokine receptors, and are activated by cytokine binding to the receptors. The major downstream pathways of JAKs are STATs and Ras-ERK. Activated STATs are translocated to the nucleus from the cytoplasm and work as transcription factors. The Ras-ERK pathway activated various transcription factors, including AP-1. (B) There are four types of JAKs and six types of STATs, and their combination depends on the cytokine receptors.