A novel H28Y mutation in LEC rats leads to decreased NAT protein stability in vivo and in vitro.
Nocturnal melatonin production is reportedly controlled by the rhythms of serotonin N-acetyltransferase (NAT, or arylalkylamine N-acetyltransferase). While analyzing the melatonin synthetic pathways of Long Evans cinnamon (LEC) rats mutant for PINA, a pineal night-specific ATPase defective in Wilson disease, we discovered that NAT activity and protein levels are greatly reduced in LEC rats, and that the highly conserved histidine 28 is mutated to tyrosine. To study the effect of H28Y, we isolated a new strain of rat termed LPN that is mutant for NAT but wildtype for both PINA and coat color. Compared with control rats, the LPN rats displayed low NAT protein levels and enzyme activities. These results suggest that the H28Y mutation in NAT is the cause of reduced NAT levels in vivo. The identical H28Y mutation was also found in Sprague-Dawley rats from Zivic-Miller, suggesting it may be a common mutation in rodents. When analyzed in bacterial cells and HEK293 cells, the mutation resulted in reduction of both NAT protein stability and catalytic activity, confirming that the in vivo NAT phenotype in LPN rats was due to the H28Y mutation. Further analysis of the NAT-H28Y will focus on the mechanisms of the increased degradation both in vitro and in vivo, which will facilitate our understanding of how melatonin synthesis is controlled at the molecular level.
Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109-0622, USA.
Zheping
Z
Huang
Jie
J
Deng
Jimo
J
Borjigin
D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000096:biosynthesis*; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D000073840:Copper-Transporting ATPases; D015536:Down-Regulation / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D006527:Hepatolenticular Degeneration / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008550:Melatonin / Q000096:biosynthesis / Q000235:genetics; D017354:Point Mutation; D051381:Rats; D020332:Rats, Inbred LEC; D017207:Rats, Sprague-Dawley
D027682:Cation Transport Proteins; C478879:AANAT protein, human; D047068:Arylalkylamine N-Acetyltransferase; D000251:Adenosine Triphosphatases; D000073840:Copper-Transporting ATPases; D008550:Melatonin