Characterizing the Effect of Knocking Down SLC35B4 Orthologs in Drosophila melanogaster

Abstract

SLC35B4 is a transmembrane solute carrier responsible for transporting nucleotide sugars, UDP-Xylose and UDP-N-acetylglucosamine, to the endoplasmic reticulum and/or Golgi apparatus. It provides the substrate for glycosyltransferases, allowing the glycosylation of glycoproteins, glycolipids, proteoglycans, glycosaminoglycans and regulating several biological processes. It has been shown to be implicated in chronic diseases such as diabetes, schizophrenia, and various types of malignancies, including glioma, hepatic, colorectal, prostate and gastric cancer. Although it was shown to have a critical role in neuroprotection against injuries and diseases by providing astrocyte-glial communication through maintaining healthy mitochondrial transfer, it has not been well studied in terms of brain function and behavior. Given the crucial urge to understand its function in an invertebrate model to later extrapolate to mammalian models, adding to that the ease of genetic manipulation and assessment provided by a variety of tools, Drosophila melanogaster is shown to be an attractive model to use when studying brain structure and function. One of the transporter’s ortholog, Efr - transporting UDP-N- acetylglucosamine, GDP-fucose and UDP-xylose - is partially involved in glycosaminoglycan synthesis and in regulating NOTCH signaling through O- fucosylation when knocked down in wing discs. It was shown that null mutations of glycosylation enzymes affect neuronal function, life span, sleep, behavior, and brain development, such as GlcNAcylation enzymes. Yet, the effect of this sugar transporter and its homolog has not been studied, being the substrate source of such glycosylation processes. In this study, we aimed to characterize the effect of knocking down (Efr-KD, CG14511-KD) on flies’ behavior, brain, and to assess the potential implications on the transporters’ functionality. Additionally, we also sought to gain indirect insights into the potential substrates that CG14511 might be transporting. Our findings revealed that knocking down SLC35B4 orthologs disrupts the flies’ behavior, with CG14511-KD additionally displaying brain enlargement. Furthermore, our preliminary data suggested the involvement of this protein in transporting UDP-N-acetylglucosamine and a potential role in NOTCH signaling. Molecularly, we suggested that SLC35B4 orthologs might interact with Hippo and TOR pathway possibly by Yorkie; Moreover, we proposed that the prolonged and better-quality life that is mainly shown in upon Efr-KD is also linked to TOR pathway. Therefore, this highlights the role of these orthologs in cancer promotion and anti-aging processes.