DeJong Randall J, Miller Lisa M, Molina-Cruz Alvaro, Gupta Lalita, Kumar Sanjeev, Barillas-Mury Carolina
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852-8132, USA.
Proc Natl Acad Sci U S A. 2007 Feb 13;104(7):2121-6. doi: 10.1073/pnas.0608407104. Epub 2007 Feb 6.
The mosquito Anopheles gambiae is a primary vector of Plasmodium parasites in Africa. The effect of aging on reproductive output in A. gambiae females from three strains that differ in their ability to melanize Plasmodium and in their systemic levels of hydrogen peroxide (H2O2), a reactive oxygen species (ROS), was analyzed. The number of eggs oviposited after the first blood meal decreases with age in all strains; however, this decline was much more pronounced in the G3 (unselected) and R (refractory to Plasmodium infection) strains than in the S (highly susceptible to Plasmodium) strain. Reduction of ROS levels in G3 and R females by administration of antioxidants reversed this age-related decline in fecundity. The S and G3 strains were fixed for two functionally different catalase alleles that differ at the second amino acid position (Ser2Trp). Biochemical analysis of recombinant proteins revealed that the Trp isoform has lower specific activity and higher Km than the Ser isoform, indicating that the former is a less efficient enzyme. The Trp-for-Ser substitution appears to destabilize the functional tetrameric form of the enzyme. Both alleles are present in the R strain, and Ser/Ser females had significantly higher fecundity than Trp/Trp females. Finally, a systemic reduction in catalase activity by dsRNA-mediated knockdown significantly reduced the reproductive output of mosquito females, indicating that catalase plays a central role in protecting the oocyte and early embryo from ROS damage.
冈比亚按蚊是非洲疟原虫的主要传播媒介。分析了衰老对来自三种品系的冈比亚按蚊雌蚊生殖产出的影响，这三种品系在黑化疟原虫的能力以及过氧化氢（H2O2，一种活性氧物质，ROS）的全身水平方面存在差异。在所有品系中，首次吸血后产卵的数量都会随着年龄的增长而减少；然而，这种下降在G3（未选择）和R（对疟原虫感染具有抗性）品系中比在S（对疟原虫高度易感）品系中更为明显。通过给予抗氧化剂降低G3和R雌蚊体内的ROS水平，逆转了这种与年龄相关的繁殖力下降。S和G3品系在第二个氨基酸位置（Ser2Trp）存在两种功能不同的过氧化氢酶等位基因。对重组蛋白的生化分析表明，色氨酸异构体的比活性低于丝氨酸异构体，Km值高于丝氨酸异构体，这表明前者是一种效率较低的酶。色氨酸替代丝氨酸似乎会破坏该酶的功能性四聚体形式。两种等位基因都存在于R品系中，丝氨酸/丝氨酸雌蚊的繁殖力显著高于色氨酸/色氨酸雌蚊。最后，通过dsRNA介导的敲低过氧化氢酶活性，全身性降低过氧化氢酶活性显著降低了雌蚊的生殖产出，表明过氧化氢酶在保护卵母细胞和早期胚胎免受ROS损伤方面起着核心作用。
