Figure 3

Schematic illustration of IGF-I signaling pathway in nurse cell formation. The binding of IGF-I to IGF-I receptor induces phosphorylation of the receptor, which acts through MAP-kinase kinase and/or PI3-K. Via the MAP kinase pathway, it activates cell cycle progression genes (cyclin D, cdc4, c-fos and c-jun) which proliferates satellite cells after Trichinella infection. Via the PI3-K/Akt pathway, it modulates the expression of muscle differentiation genes (p21, MyoD, Mef-2 and myogenin) which involve in the redifferentiation of satellite cells and differentiation of infected muscle cells. Also the activation of PI3-K/Akt inhibits proapoptosis by Bcl-2 family (Bax, Bad) and induces anti-apoptotic function by Bcl-2 family (Bcl-X), which contributes to the survival of nurse cells. This figure referred the review by Mourkioti and Rosenthal [70].