Expression and Modulation of Protein Kinase C Isoforms in Differentiation-Competent and Differentiation-Resistant Erythroleukemic Cells

Abstract

We have investigated eight of the protein kinase C (PKC) isoforms in Friend virus immortalized erythroleukemia cells. Using Western analysis, we detected the presence of the α, δ, ϵ, ζ and θ isoforms with no β, γ η. We compared levels and modulations of these isoforms among 2 lines with different susceptibilities to DMSO-induced differentiation, a cell line rendered differentiation resistant by constitutive expression of an exogenous c-myb gene and cell lines naturally resistant to differentiation. These comparisons have shown that DMSO-induced differentiation is associated with downregulation of the δ, ϵ and θ isoforms. High levels of c-myb expression prevent the downregulation of ϵ, but not δ and θ, and also appear to have resulted in lower constitutive levels of PKC α. These results help define which isoforms are important and provide clues as to what point in the signal transduction pathway they may be acting relative to another element, c-myb.