The protein kinase C (PKC) family: PKC family is a subgroup of the AGC serine-threonine kinases that consists of 10 distinct members in mammals (Spitaler and Cantrell, 2004). They all contain a C-terminal catalytic domain that is connected to the N-terminal regulatory domains. PKCs are subdi-vided into three classes according to their structures and activators. The classical/conventional PKC isoforms possess tandem C1 domains that bind to their well-known activators diacylglycerol and phorbol esters and also contain a C2 domain that mediates the binding of Ca2+-sensitive anionic phospholipids. Novel PKC isoforms also contain C1 domains that bind diacylglycerol and a novel C2 domain that does not coordinate Ca2+. Unlike the classical/conventional and novel PKC classes, atypical PKC isoforms (aPKCs) which include PKCζ and PKCι (also known as PKC λ in rodents), contain an atypical C1 domain that has no affinity to diacylglycerol or phor-bol esters. Instead of a C2 domain, a protein binding Phox/Bem domain 1 is located at the N-terminal of the regulatory region. This domain has been shown to control aPKC activity through interactions with protein adaptors at specific locations. In addition, a truncated isoform, namely protein kinase Mζ (PKMζ), is generated in the nervous system through a neuronal-tissue specific altative transcription start site in PRKCZ gene. Since all the N-terminal regulatory domains are omitted in the altative transcription, PKMζ functions as a constitutively active form of PKCζ (Figure 1).