Vol. 57, Issue 5, 961-967, May 2000

Activation of Signal Transducers and Activators of Transcription by _1A-Adrenergic Receptor Stimulation in PC12 Cells

Hongying Zhong, T. J. Murphy,¹ and Kenneth P. Minneman

Department of Pharmacology, Emory University, Atlanta, Georgia

In PC12 cells stably expressing _1A-adrenergic receptors (ARs), norepinephrine (NE) activates several mitogen-activated protein kinase pathways and causes differentiation (Williams et al., 1998). Using retroviral luciferase reporters, we found that NE also activated both signal transducers and activators of transcription (Stat) and -interferon-activated sequence-mediated transcriptional responses, with maximal effects similar to those caused by interleukin-6 (IL-6). UTP and epidermal growth factor had no effect, whereas nerve growth factor caused a small Stat activation. Responses to NE were blocked by prazosin and depended on receptor density. Responses to NE were not blocked by inhibitors of mitogen-activated protein kinase kinase (PD98059), protein kinase C (GFX203290), Src (PP2), Jak2 (AG490), or the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. The p38 mitogen-activated protein kinase inhibitors SB202190 and SB203580 blocked Stat activation by NE, the epidermal growth factor receptor inhibitor AG1478 caused a small inhibition, but the phosphoinositide 3 kinase inhibitor LY294002 potentiated both responses. Gel shifts confirmed formation of nuclear factors binding to both Stat and -interferon-activated sequence consensus sequences in response to NE and IL-6. Immunoprecipitation experiments showed that IL-6 increased tyrosine phosphorylation of Stat1 and Stat3 in PC12 cells, whereas NE caused a sustained increase in tyrosine phosphorylation of Stat1. These results suggest that _1A-AR stimulation causes Stat-mediated transcriptional responses in PC12 cells that are not downstream of known second messenger or tyrosine kinase pathways.