Identification of aaNAT5b as a spermine N-acetyltransferase in the mosquito, Aedes aegypti.

Huai Guan,Prajwalini Mehere,Chenghong Liao,Jing Liang,Jianyong Li,Meiling Tian,Hairong Liu,Qian Han,Howard Robinson,Maoying Wang,Pedro L Oliveira

doi:10.1371/journal.pone.0194499

Abstract

Mosquitoes transmit a number of diseases in animals and humans, including Dengue, Chikungunya and Zika viruses that affect millions of people each year. Controlling the disease-transmitting mosquitoes has proven to be a successful strategy to reduce the viruses transmission. Polyamines are required for the life cycle of the RNA viruses, Chikungunya virus and Zika virus, and a depletion of spermidine and spermine in the host via induction of spermine N-acetyltransferase restricts their replication. Spermine N-acetyltransferase is a key catabolic enzyme in the polyamine pathway, however there is no information of the enzyme identification in any insects. Aliphatic polyamines play a fundamental role in tissue growth and development in organisms. They are acetylated by spermidine/spermine N1-acetyltransferase (SAT). In this study we provided a molecular and biochemical identification of SAT from Aedes aegypti mosquitoes. Screening of purified recombinant proteins against polyamines established that aaNAT5b, named previously based on sequence similarity with identified aaNAT1 in insects, is active to spermine and spermidine. A crystal structure was determined and used in molecular docking in this study. Key residues were identified to be involved in spermine binding using molecular docking and simulation. In addition, SAT transcript was down regulated by blood feeding using a real time PCR test. Based on its substrate profile and transcriptional levels after blood feeding, together with previous reports for polyamines required in arboviruses replication, SAT might be potentially used as a target to control arboviruses with human interference.

Highlights

The naturally occurring aliphatic polyamines classically comprise three molecules and recently agmatine was included
Aminopropyl groups are added to putrescine from the methionine derivative, decarboxylated S-adenosylmethionine, to form spermidine and spermine catalyzed by polyamine synthases
Steady-state levels of polyamines are maintained by regulation of ODC activity to alter polyamine synthesis, as well as through polyamine catabolic enzymes, including spermine N-acetyltransferase (SAT) which promotes their interconversion with putrescine or export from the cell [3]

Summary

Introduction

The naturally occurring aliphatic polyamines classically comprise three molecules (putrescine, spermidine and spermine) and recently agmatine was included. In-cell polyamine homeostasis is tightly controlled at key steps of cell metabolism It is well-known that ornithine decarboxylase (ODC, a rate-limiting enzyme for polyamine biosynthesis) activity and polyamine levels increase during tissue proliferation and decline as growth processes cease. Aminopropyl groups are added to putrescine from the methionine derivative, decarboxylated S-adenosylmethionine, to form spermidine and spermine catalyzed by polyamine synthases. In addition to their synthesis, polyamine levels and activity are regulated by their catabolism. Steady-state levels of polyamines are maintained by regulation of ODC activity to alter polyamine synthesis, as well as through polyamine catabolic enzymes, including SAT which promotes their interconversion with putrescine or export from the cell [3]

Methods

Results

Conclusion