Göran Larson
Profile Url: gran-larson
Researcher at Department of Laboratory Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Proteoglycans, a class of carbohydrate-modified proteins, often modulate growth factor signaling on the cell surface. However, the molecular mechanism by which proteoglycans regulate signal transduction is largely unknown. In this study, using a recently-developed glycoproteomic method, we found that Windpipe (Wdp) is a novel chondroitin sulfate proteoglycan (CSPG) in Drosophila. Wdp is a single-pass transmembrane protein with leucin-rich repeat (LRR) motifs and bears three CS sugar chain attachment sites in the extracellular domain. Here we show that Wdp modulates the Hedgehog (Hh) pathway. Overexpression of wdp inhibits Hh signaling in the wing disc, which is dependent on its CS chains and the LRR motifs. Conversely, loss of wdp leads to the upregulation of Hh signaling. Furthermore, knockdown of wdp increase the cell surface accumulation of Smoothened (Smo), suggesting that Wdp inhibits Hh signaling by regulating Smo stability. Our study demonstrates a novel role of CSPG in regulating Hh signaling.
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Influenza A virus (IAV) pandemics result from interspecies transmission events within the avian reservoir and further to mammals including humans. Investigating molecular virus-host interactions dictating this process and the adaptations to the new hosts that follow is vital to understand zoonotic IAV spread. Receptor incompatibility has been suggested to limit zoonotic IAV transmission from the wild bird reservoir. Other barriers to interspecies transmission, particularly within the avian system, largely remain elusive. Through assessment of infection dynamics of mallard origin IAV in two different avian hosts, coupled with studies of receptor expression and host response we aimed to reveal the host-pathogen interactions in a cross-species transmission event. We found that shedding patterns and innate immune responses were highly dependent on viral genotypes, host species and inoculation routes, but less dependent on receptor expression. Further, in contrary to the prevailing dogma we demonstrate that birds can produce a wide range of different sialylated structures also found in mammals, e.g. extended N- and O-linked Neu5Ac alpha2,6 terminated glycans. Overall, receptor incompatibility is not the sole transmission barrier for IAV between birds and to humans, but other host-pathogen factors deserve dedicated studies to achieve proper pandemic preparedness. ### Competing Interest Statement The authors have declared no competing interest.
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Supplemental Information
Proteoglycans are structurally and functionally diverse biomacromolecules found abundantly on cell membranes and in the extracellular matrix. They consist of a core protein linked to glycosaminoglycan chains via a tetrasaccharide linkage region. Here, we show that CRISPR/Cas9-mediated b3galt6 knock-out zebrafish, lacking galactosyltransferase II, which adds the third sugar in the linkage region, largely recapitulate the phenotypic abnormalities seen in human β3GalT6-deficiency disorders. These comprise craniofacial dysmorphism, generalized skeletal dysplasia, skin involvement and indications for muscle hypotonia. In-depth TEM analysis revealed disturbed collagen fibril organization as the most consistent ultrastructural characteristic throughout different affected tissues. Strikingly, despite a strong reduction in glycosaminoglycan content, as demonstrated by anion-exchange HPLC, subsequent LC-MS/MS analysis revealed a small amount of proteoglycans containing a unique linkage region consisting of only three sugars. This implies that formation of glycosaminoglycans with an immature linkage region is possible in a pathogenic context. Our study therefore unveils a novel rescue mechanism for proteoglycan production in the absence of galactosyltransferase II, hereby opening new avenues for therapeutic intervention. ### Competing Interest Statement The authors have declared no competing interest.
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Supplementary Information containing Extended Methods and Supplementary Figures (S1-S6)
Glycoproteome profiling (glycoproteomics) remains a considerable analytical challenge that hinders rapid progress in glycobiology. The complex tandem mass spectra generated from glycopeptide mixtures require sophisticated analysis pipelines for structural determination. Diverse informatics solutions aiding the process have appeared, but their relative strengths and weaknesses remain untested. Conducted through the Human Proteome Project - Human Glycoproteomics Initiative, this community study comprising both developers and expert users of glycoproteomics software is the first to evaluate the relative performance of current informatics solutions for comprehensive glycopeptide analysis. High-quality LC-MS/MS-based glycoproteomics datasets of N- and O-glycopeptides from serum proteins were shared with all teams. The relative team performance for efficient glycopeptide data analysis was systematically established through multiple orthogonal performance tests. Excitingly, several high-performance glycoproteomics informatics solutions and tools displaying a considerable performance potential were identified. While the study illustrated that significant informatics challenges remain in the analysis of glycopeptide data as indicated by a high discrepancy between the reported glycopeptides, a substantial list of commonly reported high-confidence glycopeptides could be extracted from the team reports. Further, the team performance profiles were correlated to the many study variables, which revealed important performance-associated search settings and search output variables, some intuitive others unexpected. This study concludes that diverse informatics solutions for comprehensive glycopeptide data analysis exist within the community, points to several high-performance search strategies, and specifies key variables that may guide future software developments and assist the experimental decision-making of practitioners in glycoproteomics.