Department of Physiology and Biophysics, Rosalind Franklin University, Chicago Medical School, North Chicago, IL 60064, USA.
Insect Biochem Mol Biol. 2013 Aug;43(8):755-67. doi: 10.1016/j.ibmb.2013.05.008. Epub 2013 Jun 6.
AeNAT5 (NCBI, ABZ81822), an orphan member of the insect-specific Nutrient Amino acid Transporter subfamily of SoLute Carrier family 6 (NAT-SLC6) and the first representative of a novel eukaryotic methionine-selective transport system (M), was cloned from cDNA of the vector mosquito, Aedes aegypti. It has orphan orthologs throughout several mosquito genomes, but not in Drosophila or outside Diptera. It shows the highest apparent affinity to L-Met (K(0.5) = 0.021 mM) and its metabolites Homocysteine and Cysteine (K(0.5) = 0.89 and 2.16 mM), but weakly interact with other substrates. It has a Na(+) - coupled mechanism (K(0.5) Na(+) ∼ 46 mM) with 1AA:1Na(+) stoichiometry that maintains ∼60% activity in Cl(-) - free media. In situ hybridization showed accumof AeNAT5 transcript in the absorptive and secretory epithelia, as well as in specific peripheral neurons and the central ganglia of mosquito larvae. The labeling pattern is distinct from that of the previously characterized AeNAT1. RNAi of AeNAT5 increases larval mortality during ecdysis and dramatically suppresses adult emergence. Our results showed that in addition to previously characterized broad spectra and aromatic amino acid selective transport systems, the mosquito NAT-SLC6 subfamily evolved a unique mechanism for selective absorption of sulfur-containing substrates. We demonstrated specific patterns of alimentary and neuronal transcription of AeNAT5 in mosquito larvae that is collateral with the indispensable function of this transporter in mosquito development.
AeNAT5（NCBI，ABZ81822）是昆虫特异性营养氨基酸转运体亚家族的孤儿成员，属于溶质载体家族 6（NAT-SLC6），也是第一个新型真核甲硫氨酸选择性转运系统（M）的代表。它是从载体蚊子埃及伊蚊的 cDNA 中克隆出来的。它在几个蚊子基因组中有孤儿直系同源物，但在果蝇或双翅目以外的地方没有。它对 L-Met（K0.5=0.021mM）及其代谢物同型半胱氨酸和半胱氨酸表现出最高的表观亲和力（K0.5=0.89 和 2.16mM），但与其他底物的相互作用较弱。它具有 Na+偶联机制（K0.5Na+∼46mM），具有 1AA:1Na+的比例，在无 Cl-的介质中保持约 60%的活性。原位杂交显示 AeNAT5 转录本在吸收和分泌上皮细胞以及特定的外围神经元和蚊子幼虫的中央神经节中积累。标记模式与先前表征的 AeNAT1 不同。AeNAT5 的 RNAi 在蜕皮期间增加幼虫死亡率，并显著抑制成虫出现。我们的结果表明，除了先前表征的广谱和芳香族氨基酸选择性转运系统外，蚊子 NAT-SLC6 亚家族还进化出了一种独特的机制，用于选择性吸收含硫底物。我们在蚊子幼虫中证明了 AeNAT5 的特定饮食和神经元转录模式，这与该转运体在蚊子发育中的不可或缺功能有关。
