Pineal protein phosphorylation during serotonin N-acetyltransferase induction.

Abstract

The activity of soluble protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) and pattern of nuclear protein phosphorylation was monitored in cultured rat pineal glands during the induction of serotonin N-acetyltransferase (acetyl-CoA:serotonin N-acetyltransferase; EC 2.3.1.5)by I-isoproterenol. A nuclear protein appears to be phosphorylated during the early stages of enzyme induction but is not phosphorylated at later stages of induction. This correlates well with the need for RNA synthesis associated with the induction process. The nuclear protein was also phosphorylated when the pineal glands were treated with dibutyryl 3':5'-cyclic AMP. The soluble protein kinase activity appeared to decline during mid-to-late stages of enzyme induction, but there was no concomitant increase in the particulate protein kinase activity.In the pineal gland of rats the activity of serotonin N-acetyltransferase (acetyl CoA:serotonin N-acetyltransferase; EC 2.3.1.5) is greatly enhanced by increased sympathetic nerve impulse flow at night (1, 2). The binding of norepinephreine to d-receptors of the pineal is thought to stimulate adenylate cyclase and the resultant rise in the cellular 3':5'-cyclic AMP concentration presumably leads to a 50-to 70-fold increase in N-acetyltransferase activity (3, 4). The cellular changes occurring between the rise and fall of cyclic AMP and the rise in enzyme activity a few hours later have not been adequately defined.The magnitude of increase in the cyclic AMP concentration and the eventual magnitude of N-acetyltransferase induction display supersensitive and subsensitive characteristics (5-7). Not only is the generation of cyclic AMP production under a sensitivity control, but also the effectiveness of cyclic AMP is relatively greater in supersensitive than in subsensitive glands (6). This suggests that some other system that is responsive to changes in the cellular cyclic AMP concentrations, such as protein kinase, is also regulated. It is generally thought that protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) mediates the response to changes in the cellular cyclic AMP content (8), and it has been demonstrated that the activity of protein kinase is higher in the supersensitive than in the subsensitive gland (9, 10). It has been suggested that protein kinase mediates the action of cyclic AMP in the induction of Nacetyltransferase activity (11). The pineal gland is a rich source of cyclic-AMP-dependent protein kinase (11).One possible mechanism by which cyclic AMP and protein kinase may be involved in enzyme induction is through translocation of the protein kinase catalytic subunit from the cytosol into the nucleus (12, 13). The protein kinase presumably alters the transcriptive activity of the nucleus regulating the synthesis Abbreviation: Cyclic AMP, adenosine 3':5'-cyclic monophosphate. of RNA essential to the cellular changes induced by the original hormonal stimulus (12,14,15). Alterations in the phosphoprotein pattern of the nuclear nonhistone chromosomal proteins h...

Effects of Stimulation of the Superior Cervical Ganglia and Local Application of Noradrenaline on Electrical Activity of the Syrian Hamster Pineal Gland

“…The inhibition of continuously active pineal units observed in this study is in agreement with data obtained under similar conditions in the guinea-pig (13) although we found little evidence for excitation of pineal cells by NA. The time-course of the majority of electrical responses to N A indicates second messenger action and not direct channel gating: This is consistent with a-and /?-noradrenergic receptor actions (39,40) as well as with a second messenger-induced initiation of a biochemical change (41). On the other hand the occurrence of orthodromically driven responses to electrical stimulation of the SCG, indicates that some pineal cells may possess ligand-gated ion channels.…”

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…5). With the decrease in cAMP levels and PKA activity (Winters et al, 1977), AA-NAT is dephosphorylated, released from the 14-3-3 protein, and then subjected to a rapid proteolysis by the cytosolic proteasome Ganguly et al, 2001Ganguly et al, , 2002. The decrease in AA-NAT activity is immediately followed by a decline in MEL synthesis and release.…”

Protein Phosphorylation in Rat Pineal Gland and Its Regulation in Supersensitive and Subsensitive States

“…Recently, the phosphorylation of a specific nuclear protein with a molecular weight of 34K during SNAT induction (Winters et al, 1977), and a diurnal variation in the content of pineal Synapsin I (Nestler et al, 1982), an endogenous substrate for both cyclic AMP and calcium/calmodulin (CM)-dependent protein kinases (Krueger et al, 1977;Ueda and Greengard, 1977;, have been reported. Moreover, also CM activity has been found in the rat pineal gland as well as in several other regions of the brain (Zhou et al, 1985).…”