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Melatonin production: proteasomal proteolysis in serotonin N-acetyltransferase regulation
J A Gastel1, P H Roseboom, P A Rinaldi
1Section on Neuroendocrinology, Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, MD 20892-4480, USA.
Abstract:
The nocturnal increase in circulating melatonin in vertebrates is regulated by 10- to 100-fold increases in pineal serotonin N-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 beta-adrenergic blockade, both AA-NAT activity and protein decreased rapidly. Effects of L-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.