Abstract
Euxanthone, a potent neuritogenic compound isolated from the roots of the medicinal
herb Polygala caudata, has recently been shown to induce the differentiation of murine neuroblastoma Neuro
2A (BU-1) cells. In this study, the role of protein kinase C (PKC) and the expression
of various PKC isoforms in euxanthone-treated BU-1 cells were examined. mRNA phenotyping
using the reverse-transcription polymerase chain reaction (RT-PCR) showed that BU-1
cells express six different PKC isoforms, namely PKC-α, -β, -δ, -ε, -λ, and -ζ. Differential
regulation and expression of PKC isoforms was observed in BU-1 cells treated with
100 μM euxanthone. PKC-α, -β, -δ, -λ and -ζ were all up-regulated, with 1.7- to 9.5-fold
increase, at around 30 to 60 minutes after euxanthone treatment. The expression level
of PKC-ε remained relatively constant during the treatment. PKC-γ, -η, and -Θ were
not detected in both untreated and euxanthone-treated BU-1 cells. Staurosporine, a
broad spectrum PKC inhibitor, was found to inhibit both spontaneous and euxanthone-induced
neuritogenesis in BU-1 cells. A significant reduction of the euxanthone-induced neuritogenic
effect was also observed when the PKC isoform-specific inhibitor Go6976 was included
in the culture. These results suggest that the euxanthone-induced differentiation
of the neuroblastoma BU-1 cells may be mediated through the differential expression
of PKC-α, -β, -δ, -λ and -ζ isoforms.
Key words
Protein kinase C isoforms - euxanthone - differentiation - neuroblastoma cells
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Prof. K. N. Leung
Department of Biochemistry
The Chinese University of Hong Kong
Shatin
Hong Kong
Email: knleung@cuhk.edu.hk
Fax: +852-26035123