Ca2+ channel alpha 1-subunit transcripts are differentially expressed in rat pheochromocytoma (PC12) cells following nerve growth factor treatment.

In this report, we describe the effect of nerve growth factor (NGF) on the transcriptional expression of voltage-dependent Ca2+ channel alpha 1 subunits, i.e., alpha 1A, alpha 1B, alpha 1C, alpha 1D, and alpha 1E in rat pheochromocytoma (PC12) cells. Using reverse transcriptase-coupled polymerase chain reaction (RT-PCR) and class-specific Ca2+ channel oligonucleotide probes, messenger RNA levels were measured and compared to Histone H3.3 transcript which remained relatively constant over the duration of NGF treatment. Although no statistically significant differences in P-type (alpha 1A) Ca2+ channel transcript levels were observed, N-type (alpha 1B) Ca2+ channel transcript levels increased 50% over control values (P values < 0.05) at days 7 and 14. In contrast, NGF treatment resulted in decreased levels of L-type (alpha 1C and alpha 1D) transcripts with alpha 1C decreasing steadily to approximately 50% of control (P value < 0.01) by 2 weeks, while alpha 1D decreased to approximately 20% of control (P value < 0.01) after 2 days treatment. No alpha 1E Ca2+ channel transcripts were detected in PC12 cells. For comparison, PC12 cells were also treated with another differentiative growth factor, i.e., basic fibroblast growth factor (bFGF) and a nondifferentiative growth factor epidermal growth factor (EGF). In contrast to NGF, bFGF and EGF treatment had no inhibitory effect on L-type (alpha 1C and alpha 1D) channel transcript levels after 3 days. Like NGF, EGF treatment had no statistically significant effect upon P-type (alpha 1A) transcript levels but increased in a biphasic manner following bFGF treatment. Presynaptic-associated alpha 1B (N-type) Ca2+ channel transcripts were observed decreased following EGF treatment (2 days) while L-type alpha 1C transcripts decreased after 7 days (P value < 0.01). Although a varied response to differentiative growth factors NGF and bFGF was observed, data presented here indicate that NGF treatment of PC12 cells results in 'late' increased expression of N-type Ca2+ channel transcripts, while L-type (alpha 1C and alpha 1D) Ca2+ channel transcripts appear to be down regulated.