Melatonin Production: Proteasomal Proteolysis in Serotonin N-Acetyltransferase Regulation

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Science  27 Feb 1998:
Vol. 279, Issue 5355, pp. 1358-1360
DOI: 10.1126/science.279.5355.1358

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The nocturnal increase in circulating melatonin in vertebrates is regulated by 10- to 100-fold increases in pineal serotoninN-acetyltransferase (AA-NAT) activity. Changes in the amount of AA-NAT protein were shown to parallel changes in AA-NAT activity. When neural stimulation was switched off by either light exposure or l-propranolol–induced β-adrenergic blockade, both AA-NAT activity and protein decreased rapidly. Effects ofl-propranolol were blocked in vitro by dibutyryl adenosine 3′,5′-monophosphate (cAMP) or inhibitors of proteasomal proteolysis. This result indicates that adrenergic-cAMP regulation of AA-NAT is mediated by rapid reversible control of selective proteasomal proteolysis. Similar proteasome-based mechanisms may function widely as selective molecular switches in vertebrate neural systems.

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