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Human T-cell leukemia virus type-1 (HTLV-1) is the first pathogenic retrovirus discovered in human. Although HTLV-1-induced diseases are well characterized and linked to the encoded Tax-1 protein, there is currently no strategy to target Tax-1 functions with small molecules. Here, we report a comprehensive interaction map between Tax-1 and human PDZ domain-containing proteins (hPDZome), and we show that Tax-1 interacts with one-third of them. This includes proteins involved in cell cycle, cell-cell junction and cytoskeleton organization, as well as in membrane complexes assembly. Using nuclear magnetic resonance (NMR) spectroscopy, we have determined the structural basis of the interaction between the C-terminal PDZ binding motif (PBM) of Tax-1, and the PDZ domains of DLG1 and syntenin-1. Finally, we have used molecular modeling and mammalian cell-based assays to demonstrate that Tax-1/PDZ-domain interactions are amenable to small-molecule inhibition. Thus, our work provides a framework for the design of targeted therapies for HTLV-1-induced diseases. HighlightsO_LIcomprehensive interactome map of HTLV-1 Tax / human PDZ proteins C_LIO_LIbasis of Tax-1 PBM binding to human DLG1 and syntenin-1 PDZ domains". C_LIO_LIsignificance of inhibiting Tax-1 functions C_LIO_LIof the Tax-1 / PDZ interface C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/457680v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@6ba754org.highwire.dtl.DTLVardef@1b68124org.highwire.dtl.DTLVardef@d873c6org.highwire.dtl.DTLVardef@98f7ae_HPS_FORMAT_FIGEXP M_FIG C_FIG

Integration of multiomics and imaging identifies a glycosyltransferase enzyme regulating endoplasmic reticulum sizes., The endoplasmic reticulum (ER) is a central eukaryotic organelle with a tubular network made of hairpin proteins linked by hydrolysis of guanosine triphosphate nucleotides. Among posttranslational modifications initiated at the ER level, glycosylation is the most common reaction. However, our understanding of the impact of glycosylation on the ER structure remains unclear. Here, we show that exostosin-1 (EXT1) glycosyltransferase, an enzyme involved in N-glycosylation, is a key regulator of ER morphology and dynamics. We have integrated multiomics and superresolution imaging to characterize the broad effect of EXT1 inactivation, including the ER shape-dynamics-function relationships in mammalian cells. We have observed that inactivating EXT1 induces cell enlargement and enhances metabolic switches such as protein secretion. In particular, suppressing EXT1 in mouse thymocytes causes developmental dysfunctions associated with the ER network extension. Last, our data illuminate the physical and functional aspects of the ER proteome-glycome-lipidome structure axis, with implications in biotechnology and medicine.

SUMMARYThe endoplasmic reticulum (ER) is a central eukaryotic organelle with a tubular network made of hairpin proteins linked by hydrolysis of GTP nucleotides. Among post-translational modifications initiated at the ER level, glycosylation is the most common reaction. However, our understanding of the impact of glycosylation on ER structure remains unclear. Here, we show that Exostosin-1 (EXT1) glycosyltransferase, an enzyme involved inN-glycosylation, is a key regulator of ER morphology and dynamics. We have integrated multi-omics data and super-resolution imaging to characterize the broad effect of EXT1 inactivation, including ER shape-dynamics-function relationships in mammalian cells. We have observed that, inactivating EXT1 induces cell enlargement and enhances metabolic switches such as protein secretion. In particular, suppressing EXT1 in mouse thymocytes causes developmental dysfunctions associated to ER network extension. Our findings suggest that EXT1 drives glycosylation reactions involving ER structural proteins and high-energy nucleotide sugars, which might also apply to other organelles.