Metabolic pathways in Anopheles stephensi mitochondria

Abstract

No studies have been performed on the mitochondria of malaria vector mosquitoes. This information would be valuable in understanding mosquito aging and detoxification of insecticides, two parameters that have a significant impact on malaria parasite transmission in endemic regions. In the present study, we report the analyses of respiration and oxidative phosphorylation in mitochondria of cultured cells [ASE (Anopheles stephensi Mos. 43) cell line] from A. stephensi, a major vector of malaria in India, South-East Asia and parts of the Middle East. ASE cell mitochondria share many features in common with mammalian muscle mitochondria, despite the fact that these cells are of larval origin. However, two major differences with mammalian mitochondria were apparent. One, the glycerol-phosphate shuttle plays as major a role in NADH oxidation in ASE cell mitochondria as it does in insect muscle mitochondria. In contrast, mammalian white muscle mitochondria depend primarily on lactate dehydrogenase, whereas red muscle mitochondria depend on the malate-oxaloacetate shuttle. Two, ASE mitochondria were able to oxidize proline at a rate comparable with that of alpha-glycerophosphate. However, the proline pathway appeared to differ from the currently accepted pathway, in that oxoglutarate could be catabolized completely by the tricarboxylic acid cycle or via transamination, depending on the ATP need.

Figure 1

Schematic representation of proline metabolism in ASE mitochondria Panel A: Proline metabolism as described by [–44, 47, 71]. Panel B: Proline metabolism expanded and modified according to the experimental results found in this study. Inhibitors are shown in italics. 1, Δ¹-pyrroline-5-carboxylate reductase; 2, Δ¹-pyrroline-5-carboxylate dehydrogenase; 3, Glutamate-pyruvate transaminase; 4, ketoglutarate dehydrogenase; 5, succinylCoA synthetase; 6, succinate dehydrogenase; 7, fumarate reductase; 8, malic enzyme; 9, malate dehydrogenase; 10, citrate synthase; 11, aconitase; 12, isocitrate dehydrogenase; 13, pyruvate dehydrogenase; 14, aspartate-oxaloacetate transaminase; 15, glutamate dehydrogenase.

Figure 1

Schematic representation of proline metabolism in ASE mitochondria Panel A: Proline metabolism as described by [–44, 47, 71]. Panel B: Proline metabolism expanded and modified according to the experimental results found in this study. Inhibitors are shown in italics. 1, Δ¹-pyrroline-5-carboxylate reductase; 2, Δ¹-pyrroline-5-carboxylate dehydrogenase; 3, Glutamate-pyruvate transaminase; 4, ketoglutarate dehydrogenase; 5, succinylCoA synthetase; 6, succinate dehydrogenase; 7, fumarate reductase; 8, malic enzyme; 9, malate dehydrogenase; 10, citrate synthase; 11, aconitase; 12, isocitrate dehydrogenase; 13, pyruvate dehydrogenase; 14, aspartate-oxaloacetate transaminase; 15, glutamate dehydrogenase.