Nerve growth factor decreases soluble guanylate cyclase in rat pheochromocytoma PC12 cells

Nitric oxide (NO) modulates neurotransmission in the central and peripheral nervous systems. NO acts, in part, by stimulating cGMP production by soluble guanylate cyclase (sGC), an obligate heterodimer composed of alpha and beta subunits. To investigate mechanisms that regulate responsiveness to NO in the nervous system, sGC regulation was examined in a rat pheochromocytoma cell line (PC12) exposed to nerve growth factor (NGF). NGF decreased sGC alpha1 and beta1 subunit mRNA and protein levels as well as NO-stimulated sGC enzyme activity. The NGF-mediated decrease in sGC subunit mRNA levels was blocked by 5'-deoxy-5'-methylthioadenosine (an inhibitor of NGF-induced tyrosine phosphorylation). NGF did not decrease sGC subunit mRNA levels in PC12 cells containing a mutant Ras protein that blocks Ras-dependent intracellular signaling. Incubation of PC12 cells with a transcription inhibitor (actinomycin D) or protein synthesis inhibitors (anisomycin or cycloheximide) attenuated the ability of NGF to decrease sGC subunit mRNA levels. Moreover, sGC subunit mRNA levels decreased more rapidly in NGF-treated cells than in actinomycin D-treated cells, suggesting that NGF decreases sGC subunit mRNA stability. Thus, NGF decreases sGC subunit mRNA levels via mechanisms that are dependent on protein tyrosine phosphorylation and Ras activation. The effect of NGF on sGC subunit mRNA stability appears to be transcription- and translation-dependent. Modulation of sGC subunit levels and enzyme activity in PC12 cells suggests that NO responsiveness may be regulated in the nervous system by NGF.