Activation of increases production via adenylyl cyclase activation and inhibits monoamine transporter function. Ras activates the MAPK cascade which results in increased p53 activation and p16 upregulation. This results in the activation of SREBP-2-mediated signaling pathways. This coupled with NFAT signaling allows for complete activation of the IL-2 gene. Both are mediated via G protein activation. "NFAT" activation depends on calcium signaling. Expression of some molecules may change in course of the mast cell activation. There is both a head and foot activation and inhibition gradient. Botulinum toxin exerts its effect by cleaving key proteins required for nerve activation. Influenza A also blocks protein kinase R activation and establishment of the antiviral state. This leads to stellate cell activation and fibrogenesis. It does this by inhibiting platelet activation. Cytokines play a crucial role in NK cell activation. This process is commonly referred to as transcriptional activation, or transactivation. It is also involved in the activation of protein kinases.