Activity Detection of GalNAc Transferases by Protein-Based Fluorescence Sensors In Vivo.
Ontology highlight
ABSTRACT:
SUBMITTER: Song L
PROVIDER: S-EPMC5549557 | biostudies-other | 2016
REPOSITORIES: biostudies-other
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Project description:Protein O-glycosylation is controlled by polypeptide GalNAc-transferases (GalNAc-Ts) that uniquely feature both a catalytic and lectin domain. The underlying molecular basis of how the lectin domains of GalNAc-Ts contribute to glycopeptide specificity and catalysis remains unclear. Here we present the first crystal structures of complexes of GalNAc-T2 with glycopeptides that together with enhanced sampling molecular dynamics simulations demonstrate a cooperative mechanism by which the lectin domain enables free acceptor sites binding of glycopeptides into the catalytic domain. Atomic force microscopy and small-angle X-ray scattering experiments further reveal a dynamic conformational landscape of GalNAc-T2 and a prominent role of compact structures that are both required for efficient catalysis. Our model indicates that the activity profile of GalNAc-T2 is dictated by conformational heterogeneity and relies on a flexible linker located between the catalytic and the lectin domains. Our results also shed light on how GalNAc-Ts generate dense decoration of proteins with O-glycans.
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Project description:To metastasize, a tumor cell must acquire abilities such as the capacity to colonize new tissue and evade immune surveillance. Recent evidence suggests that microRNAs can promote the evolution of malignant behaviors by regulating multiple targets. We performed a microRNA analysis of human melanoma, a highly invasive cancer, and found that miR-30b/30d upregulation correlates with stage, metastatic potential, shorter time to recurrence, and reduced overall survival. Ectopic expression of miR-30b/30d promoted the metastatic behavior of melanoma cells by directly targeting the GalNAc transferase GALNT7, resulted in increased synthesis of the immunosuppressive cytokine IL-10, and reduced immune cell activation and recruitment. These data support a key role of miR-30b/30d and GalNAc transferases in metastasis, by simultaneously promoting cellular invasion and immunosuppression.
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Project description:To metastasize, a tumor cell must acquire abilities such as the capacity to colonize new tissue and evade immune surveillance. Recent evidence suggests that microRNAs can promote the evolution of malignant behaviors by regulating multiple targets simultaneously. We performed a microRNA analysis of human melanoma, an aggressively invasive cancer, and found that miR-30b/30d upregulation correlates with stage, metastatic potential of primary tumors, shorter time to recurrence and reduced overall survival. Ectopic expression of miR-30b/30d promoted the metastatic behavior of melanoma cells by directly targeting the GalNAc transferase GALNT7, resulted in increased synthesis of the immunosuppressive cytokine IL-10, and reduced immune cell activation and recruitment. These data point to a key role of miR-30b/30d and GalNAc transferases in metastasis, by simultaneously promoting cellular invasion and immune suppression. MicroRNAs are emerging as key contributors to tumor metastasis because of their ability to regulate multiple targets, and thereby alter several functions, simultaneously. We found a miRNA cluster that promotes metastasis by concurrently enhancing invasive capabilities of melanoma cells and suppressing immune surveillance mechanisms, allowing the tumor cells to migrate and invade foreign tissue. Both these effects of miR-30b/30d are mediated by direct suppression of GalNAc transferases. Aberrant glycosylation has previously been connected to tumor progression, but the underlying molecular mechanisms and their impact on specific cellular pathways are poorly understood. Our work places the control of glycosylation as a novel molecular link between tumor cell migration and immune evasion, two processes that act synergistically during metastasis.
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Project description:Our knowledge of the O-glycoproteome [N-acetylgalactosamine (GalNAc) type] is highly limited. The O-glycoproteome is differentially regulated in cells by dynamic expression of a subset of 20 polypeptide GalNAc-transferases (GalNAc-Ts), and methods to identify important functions of individual GalNAc-Ts are largely unavailable. We recently introduced SimpleCells, i.e., human cell lines made deficient in O-glycan extension by zinc finger nuclease targeting of a key gene in O-glycan elongation (Cosmc), which allows for proteome-wide discovery of O-glycoproteins. Here we have extended the SimpleCell concept to include proteome-wide discovery of unique functions of individual GalNAc-Ts. We used the GalNAc-T2 isoform implicated in dyslipidemia and the human HepG2 liver cell line to demonstrate unique functions of this isoform. We confirm that GalNAc-T2-directed site-specific O-glycosylation inhibits proprotein activation of the lipase inhibitor ANGPTL3 in HepG2 cells and further identify eight O-glycoproteins exclusively glycosylated by T2 of which one, ApoC-III, is implicated in dyslipidemia. Our study supports an essential role for GalNAc-T2 in lipid metabolism, provides serum biomarkers for GalNAc-T2 enzyme function, and validates the use of GALNT gene targeting with SimpleCells for broad discovery of disease-causing deficiencies in O-glycosylation. The presented glycoengineering strategy opens the way for proteome-wide discovery of functions of GalNAc-T isoforms and their role in congenital diseases and disorders.
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Project description:To metastasize, a tumor cell must acquire abilities such as the capacity to colonize new tissue and evade immune surveillance. Recent evidence suggests that microRNAs can promote the evolution of malignant behaviors by regulating multiple targets simultaneously. We performed a microRNA analysis of human melanoma, an aggressively invasive cancer, and found that miR-30b/30d upregulation correlates with stage, metastatic potential of primary tumors, shorter time to recurrence and reduced overall survival. Ectopic expression of miR-30b/30d promoted the metastatic behavior of melanoma cells by directly targeting the GalNAc transferase GALNT7, resulted in increased synthesis of the immunosuppressive cytokine IL-10, and reduced immune cell activation and recruitment. These data point to a key role of miR-30b/30d and GalNAc transferases in metastasis, by simultaneously promoting cellular invasion and immune suppression. MicroRNAs are emerging as key contributors to tumor metastasis because of their ability to regulate multiple targets, and thereby alter several functions, simultaneously. We found a miRNA cluster that promotes metastasis by concurrently enhancing invasive capabilities of melanoma cells and suppressing immune surveillance mechanisms, allowing the tumor cells to migrate and invade foreign tissue. Both these effects of miR-30b/30d are mediated by direct suppression of GalNAc transferases. Aberrant glycosylation has previously been connected to tumor progression, but the underlying molecular mechanisms and their impact on specific cellular pathways are poorly understood. Our work places the control of glycosylation as a novel molecular link between tumor cell migration and immune evasion, two processes that act synergistically during metastasis. 2 different melanoma cell line, 2 biological duplicates for each cell line Differentially expressed genes (mRNAs) in response to miRNA over-expression
2011-03-08 | E-GEOD-27718 | biostudies-arrayexpress
Project description:The polypeptide GalNAc-transferases (GalNAc-Ts), that initiate mucin-type O-glycosylation, consist of a catalytic and a lectin domain connected by a flexible linker. In addition to recognizing polypeptide sequence, the GalNAc-Ts exhibit unique long-range N- and/or C-terminal prior glycosylation (GalNAc-O-Ser/Thr) preferences modulated by the lectin domain. Here we report studies on GalNAc-T4 that reveal the origins of its unique N-terminal long-range glycopeptide specificity, which is the opposite of GalNAc-T2. The GalNAc-T4 structure bound to a monoglycopeptide shows that the GalNAc-binding site of its lectin domain is rotated relative to the homologous GalNAc-T2 structure, explaining their different long-range preferences. Kinetics and molecular dynamics simulations on several GalNAc-T2 flexible linker constructs show altered remote prior glycosylation preferences, confirming that the flexible linker dictates the rotation of the lectin domain, thus modulating the GalNAc-Ts' long-range preferences. This work for the first time provides the structural basis for the different remote prior glycosylation preferences of the GalNAc-Ts.
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