Stimulus coupling to transcription versus secretion in pheochromocytoma cells. Convergent and divergent signal transduction pathways and the crucial roles for route of cytosolic calcium entry and protein kinase C.

Abstract

How do chromaffin cell secretory stimuli program resynthesis of secreted peptides and amines? We previously showed that the physiologic nicotinic cholinergic signal for secretion also activates the biosynthesis of chromogranin A, the major protein released with catecholamines. Here, we examine signal transduction pathways whereby secretory stimuli influence exocytotic secretion versus chromogranin A transcription. Both secretion and transcription depended on initial nicotinic-triggered sodium entry into the cytosol, followed by calcium entry through L -type voltage-gated channels. When calcium entered through L -type channels, activation of secretion paralleled activation of transcription ( r ϭ 0.897, P ϭ 0.002). Calcium entry from intracellular stores or through calcium ionophore channels activated secretion, though not transcription. Nicotinic-stimulated transcription depended upon protein kinase C activation; nicotine caused translocation of protein kinase C to the cell membrane fraction, and inhibition of protein kinase C blocked activation of transcription, while activation of protein kinase C mimicked nicotine effects. Transcriptional responses to both nicotine and protein kinase C mapped principally onto the chromogranin A promoter's cAMP response element (TGACGTAA; CRE box). KCREB, a dominant negative mutant of the CREbinding protein CREB, blunted activation of chromogranin A transcription by nicotine, phorbol ester, or membrane depolarization. We conclude that activation of chromogranin A transcription by secretory stimulation in chromaffin cells is highly dependent upon precise route of calcium entry into the cytosol; transcription occurred after entry of calcium through L -type channels on the cell surface, and was mediated by protein kinase C activation. The trans -acting factor CREB ultimately relays the secretory signal to the chromogranin A promoter's CRE box in cis. ( J. Clin. Invest.

Effects of Nicotine Administration on Striatal Dopamine Signaling after Traumatic Brain Injury in Rats

“…Nicotine has been demonstrated to induce PKC activation (Tang et al, 1997), which can phosphorylate TH and induce activation. Increase in pser40TH was shown to depend upon protein kinase C (PKC) 24 h after nicotine stimulus, whereas other kinases may contribute to pser40TH levels at earlier times (Bobrovskaya et al, 2007).…”

Catecholamine Secretory Vesicle Stimulus-Transcription Coupling in Vivo

“…In cultured chromaffin cells in vitro (7)(8)(9), exocytotic stimuli also program the resynthesis of just released catecholamine storage vesicle contents, a process known as "stimulus-secretion-synthesis coupling" or "stimulus-transcription coupling." Does this phenomenon occur in vivo?…”

“…Such nicotinic stimulation in cultured chromaffin cells in vitro (7)(8)(9) triggers the resynthesis of chromogranin A at the transcriptional level. This process of "stimulus-secretion-synthesis coupling" or "stimulus-transcription coupling" may serve to replete storage vesicles of just released transmitters (7)(8)(9).…”

“…This process of "stimulus-secretion-synthesis coupling" or "stimulus-transcription coupling" may serve to replete storage vesicles of just released transmitters (7)(8)(9).…”

“…We have characterized this process (sometimes called "stimulus-secretion-synthesis coupling" or "stimulustranscription coupling") in chromaffin cells in vitro (7)(8)(9) and established transcriptional activation of chromogranin A by nicotinic cholinergic (physiologic pathway) stimulation. The process occurs at the level of transcript initiation (7), requires particular elements in cis in the proximal promoter (7), and has well defined signal transduction pathways in trans (8,9). However, whether this nicotinic cholinergic stimulation of chromogranin A occurs in vivo is uncertain.…”