Changes in the Expression of β and Actins During Differentiation of PC 12 Cells

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Abstract
Cells of the rat pheochromocytoma line PC12 cease proliferation and develop neurites in response to nerve growth factor (NGF). Quantification of .beta. and .gamma. isoforms of nonmuscle actin in extracts of these differentiating cells showed that the .beta.:.gamma. ratio decreased from 1.30 .+-. 0.05 to 0.99 .+-. 0.05 after 6 days of NGF treatment. Cells treated with N6,O2-dibutyryl cyclic AMP (dbcAMP) also showed a shift in the ratio of .beta.:.gamma. isoforms, although few of these cells extended neurites. Administration of dbcAMP or both NGF and dbcAMP to cells accelerated the decrease in the .beta.:.gamma. actin isoform ratio relative to treatment with NGF alone. Those cells treated with both NGF and dbcAMP also showed an accelerated rate of neurite outgrowth. Suspension-grown PC12 cells treated with NGF showed neither an isoform ratio decrease nor neurite development. Our results suggest that either cyclic AMP may be "second messenger" for NGF or it may effect the isoform ratio change by an independent mechanism. In addition, our data demonstrate in alteration in actin isoform expression, which accompanies the morphological differentiation of PC12 cells.