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Non-canonical transcriptional regulation of heme oxygenase in Aedes aegypti.

ABSTRACT: Heme oxygenase (HO) is a ubiquitous enzyme responsible for heme breakdown, which yields carbon monoxide (CO), biliverdin (BV) and ferrous ion. Here we show that the Aedes aegypti heme oxygenase gene (AeHO - AAEL008136) is expressed in different developmental stages and tissues. AeHO expression increases after a blood meal in the midgut, and its maximal transcription levels overlaps with the maximal rate of the further modified A. aegypti biglutaminyl-biliverdin (AeBV) pigment production. HO is a classical component of stress response in eukaryotic cells, being activated under oxidative stress or increased heme levels. Indeed, the final product of HO activity in the mosquito midgut, AeBV, exerts a protective antioxidant activity. AeHO, however, does not seem to be under a classical redox-sensitive transcriptional regulation, being unresponsive to heme itself, and even down regulated when insects face a pro-oxidant insult. In contrast, AeHO gene expression responds to nutrient sensing mechanisms, through the target of rapamycin (TOR) pathway. This unusual transcriptional control of AeHO, together with the antioxidant properties of AeBV, suggests that heme degradation by HO, in addition to its important role in protection of Aedes aegypti against heme exposure, also acts as a digestive feature, being an essential adaptation to blood feeding.

SUBMITTER: Bottino-Rojas V

PROVIDER: S-EPMC6760526 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:After a bloodmeal, mosquitoes import heme into the midgut epithelium. Heme acts as an essential signal for oogenesis in Aedes aegypti. However, the mechanisms behind heme import in Aedes aegypti are largely unexplored. In this study, RNA sequencing data from 4 different Aedes aegypti cell culture experiments where exposure to an overabundance or deficiency of heme was examined to identify heme-responsive genes. Zinc mesoporphyrin (ZnMP), a heme fluorescent analog, was used to measure changes in heme uptake prior to mRNA sequencing. A soft cluster analysis was performed to identify genes encoding potential membrane bound importers and exporters based on expression profiles across the samples for each experiment. Stronger candidates were obtained by comparing genes in each dataset to each other. When comparing all datasets to each other, 223 candidate genes with expression pattern changes consistent with importers were found to be heme-regulated in only 2 datasets, 46 were heme-regulated in 3 datasets and 2 was heme-regulated in all 4 datasets. In contrast, 114 candidate genes with patterns consistent with exporters were common to only 2 datasets, with just 11 present in 3 of the 4 datasets. A large number of genes containing transmembrane domains were isolated across the 4 datasets which showed downregulation or upregulation in response to heme overexposure conditions indicating the possibility that heme membrane bound import and export genes were identified respectively, with the reverse trend observed in the presence of heme deficiency. However, few transporter candidate genes were identified that showed high differential expression (above 4-fold or below 1/4th fold). Ultimately, as few strong candidates were identified by these studies, we consider the possibility that each cell line could have a redundant system of heme import, whereby multiple transport proteins each contribute to the total heme accumulation in the cell. Alternatively, it is possible that these cells lines do not regulate heme transport at the transcript level, but rather do so post-translationally.

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Non-canonical transcriptional regulation of heme oxygenase in Aedes aegypti.

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