Protein kinase C (PKC) alpha phosphorylates and regulates the activity of several receptor tyrosine kinases including KIT. PKC alpha is involved in a negative feedback loop regulating SCF induced proliferation by phosphorylating and inhibiting the kinase activity of KIT (Blume-Jensen et al. 1994, 1995). PKC alpha phosphorylates KIT on S741 and S746 of the kinase insert (Blume-Jensen et al. 1995). This serine phosphorylation inhibits KIT kinase activity and reduces the capacity of multiple SH2 containing signaling components to associate with KIT (Linnekin 1999).