Functional analysis of ABCA3 transporters in lipid metabolism regulation of the silkworm, Bombyx mori.

ATP-binding cassette (ABC) transporters form one of the most widespread membrane protein families. They move a wide range of substrates across biological membranes. While members of the ABCA subfamily have been extensively linked to lipid metabolism in mammals, their functions in insects remain unclear. In this study, we investigated the function of Bombyx mori ABCA3 (BmABCA3), a full-length ABCA transporter by bioinformatic analysis, CRISPR/Cas9 knockout, lipid staining, and proteomics analysis. BmABCA3 was mainly expressed in metabolically active tissues such as the hemocytes and fat body. Loss of BmABCA3 led to growth delay, lower body weight, abnormal integument pigmentation, and increased larval death. Lipid staining showed abnormal lipid buildup in hemocytes and lipid loss in other tissues. Free fatty acid levels were also strongly disrupted. Proteomic analysis revealed changes in fatty acid metabolism, cuticle formation, and vesicle-related transport. Supplementing the diet with cholesterol partly rescued the developmental defects in knockout larvae. These findings show that BmABCA3 plays a central role in lipid metabolism and is likely involved in sterol regulation in insects. This study also broadens our understanding of the functional roles of ABC transporters.