Protein kinase C zeta (PKCzeta) plays critical roles in neural development. In the brain, many PKCzeta-related transcripts are expressed but they do not code the native 75 kDa PKCzeta molecule. We examined the significance of such transcripts in intact cells. A PKCzeta-related (PKCzetaII) cDNA, whose mRNA was specifically expressed in the brain, was obtained. When PKCzetaII cDNA was introduced to rat NRK cells using an adenovirus vector, a 50 kDa protein was detected as a truncated form of PKCzeta lacking the regulatory domain. The PKCzetaII protein was also detected in the brain, cerebellar granule neurons and neuroblastoma cells, but not in astrocytes and glioma cells. An alternative promoter for PKCzetaII was localized in intron 4 of the PKCzeta gene. The specificity of PKCzetaII expression can be regulated at the transcription level in a cell-type-specific manner.