The latest development on intracellular signal transduction mainly focus on Ca²⁺ pathways with their related protein molecules such as PKC,CaM,CaMKⅡ,and Ras with their related protein molecules(such as Vav,Rap,Crk,C3G),cAMP,NF-κB pathways as well. Through the above mentioned four pathways and the cross-talk among them,extracellular signal molecules activate some protein kinases which regulate gene transcription and other related functions.It should be noted that phosphorylation plays a significant role in regulating the activity of protein kinases and transcript factors.