Glycosphingolipids are not uniformly present in cell membranes and form microdomains called glycolipid microdomains together with sphingomyelin and cholesterol. Many signaling molecules accumulate there, and glycolipid composition greatly influences signal transmission efficiency. Therefore, analyzing the dynamics and structure of glycolipid microdomains is very important in understanding life phenomena. In recent glycolipid microdomain studies, along with biochemical methods, analysis of membrane molecular dynamics by fluorescence microscopy, localization analysis using an electron microscope, and lipid structure analysis by mass spectrometry have been conducted. In this review, I mainly introduce the glycolipid microdomain analysis method using fluorescence microscopy and mass spectrometry.

Development of regio- and stereoselective glycosylations leading to a specific hydroxyl group among several free hydroxyl groups is a challenging and long-standing research subject in carbohydrate chemistry. In this context, several efficient regio- and stereoselective glycosylation methods utilizing organoboron reagents, which can bind reversibly to cis-1,2- or 1,3-diols under mild conditions, have been reported. In this focused review article, several organoboron-mediated regio- and stereoselective glycosylations are described, including recently developed methods.

Asparagine-linked glycosylation (N-glycosylation) occurs on many secretory and membrane proteins synthesized in the endoplasmic reticulum (ER). In the past three decades, most, if not all, of the genes involved in the biosynthesis of N-glycans have been identified. However, much remains unknown about mechanisms by which N-glycosylation is regulated, thereby hampering our integrative understanding of the biological modulatory functions of this posttranslational modification. In this mini-review, I will summarize our recent knowledge on the early steps of N-glycan biosynthesis in biochemical and structural biological points of view.

The indispensable roles of glycosaminoglycans (GAGs), including chondroitin sulfate, dermatan sulfate, and heparan sulfate, have been demonstrated in various biological events such as construction of the extracellular matrix, tissue development, and cell signaling through interactions with extracellular matrix components, morphogens, and growth factors by analyses using the following model organisms: nematodes, fruit flies, frogs, zebrafish, and mice. A large number of human genetic diseases including heart defects, immune deficiencies, and neurological abnormalities in addition to connective tissue diseases such as hereditary multiple exostoses and Ehlers–Danlos syndrome were recently reported to be caused by mutations in the genes encoding glycosyltransferases, epimerases, and sulfotransferases that are responsible for the biosynthesis of GAGs. Glycobiological approaches revealed that mutations in GAG-biosynthetic enzymes led to reductions in their enzymatic activities as well as in the levels of GAGs. This review provides an overview of the growing number of glycobiological studies on recently characterized genetic disorders caused by the faulty biosynthesis of GAGs.

In carbohydrate chemistry, many useful stereoselective glycosylation methods have been developed that control the stereochemistry of the newly formed glycosylated product in chemical glycosylation. For example, in the past decade, unique stereoselective glycosylation methods have been reported that use glycosyl donors in which the ring is conformationally restricted by the di-tert-butylsilylene (DTBS) group as a cyclic silyl protecting group. To date, glycosyl donors with the DTBS group have been used to control the stereoselectivity of diverse chemical glycosylations for the formation of α-galactosides/galactosaminides, β-arabinofuranosides, α-sialosides, α-galactofuranosides, β-glucuronides, β-glucosides, β-mannosides, α-Kdo glycosides, and α-glucosides. Furthermore, the effect of ring-restriction for stereoselective glycosylations has provided new insights into the reaction mechanism of chemical glycosylation. This review provides a historical overview of stereoselective glycosylations using DTBS-tethered glycosyl donors and their application to the synthesis of biologically relevant carbohydrate molecules.

Glycans play a role in neural circuit formation and higher brain functions such as memory and learning in nervous system. Mucin-type O-glycans are present at high levels on mucins and T-cell immunoglobulin and mucin domains (TIM). Mucins are secreted from epithelial cells present in digestive organs. TIM possesses a T-cell immunoglobulin and mucin domain, and functions in the immune system. In addition, several mucin-type O-glycans are highly expressed in cancer cells and are thus used as a diagnostic marker. We previously found that T antigen, a mucin-type O-glycan, is highly expressed in the nervous system of Drosophila; however, the functions of mucin-type O-glycans in the nervous system remained largely unknown.

In this review, we describe the functions of mucin-type O-glycans in the nervous systems of mammals and invertebrates, focusing mainly on the role of T antigens in nervous system of Drosophila, which we have recently reported.

Glycosphingolipids are not uniformly present in cell membranes and form microdomains called glycolipid microdomains together with sphingomyelin and cholesterol. Many signaling molecules accumulate there, and glycolipid composition greatly influences signal transmission efficiency. Therefore, analyzing the dynamics and structure of glycolipid microdomains is very important in understanding life phenomena. In recent glycolipid microdomain studies, along with biochemical methods, analysis of membrane molecular dynamics by fluorescence microscopy, localization analysis using an electron microscope, and lipid structure analysis by mass spectrometry have been conducted. In this review, I mainly introduce the glycolipid microdomain analysis method using fluorescence microscopy and mass spectrometry.

Development of regio- and stereoselective glycosylations leading to a specific hydroxyl group among several free hydroxyl groups is a challenging and long-standing research subject in carbohydrate chemistry. In this context, several efficient regio- and stereoselective glycosylation methods utilizing organoboron reagents, which can bind reversibly to cis-1,2- or 1,3-diols under mild conditions, have been reported. In this focused review article, several organoboron-mediated regio- and stereoselective glycosylations are described, including recently developed methods.

Asparagine-linked glycosylation (N-glycosylation) occurs on many secretory and membrane proteins synthesized in the endoplasmic reticulum (ER). In the past three decades, most, if not all, of the genes involved in the biosynthesis of N-glycans have been identified. However, much remains unknown about mechanisms by which N-glycosylation is regulated, thereby hampering our integrative understanding of the biological modulatory functions of this posttranslational modification. In this mini-review, I will summarize our recent knowledge on the early steps of N-glycan biosynthesis in biochemical and structural biological points of view.

The indispensable roles of glycosaminoglycans (GAGs), including chondroitin sulfate, dermatan sulfate, and heparan sulfate, have been demonstrated in various biological events such as construction of the extracellular matrix, tissue development, and cell signaling through interactions with extracellular matrix components, morphogens, and growth factors by analyses using the following model organisms: nematodes, fruit flies, frogs, zebrafish, and mice. A large number of human genetic diseases including heart defects, immune deficiencies, and neurological abnormalities in addition to connective tissue diseases such as hereditary multiple exostoses and Ehlers–Danlos syndrome were recently reported to be caused by mutations in the genes encoding glycosyltransferases, epimerases, and sulfotransferases that are responsible for the biosynthesis of GAGs. Glycobiological approaches revealed that mutations in GAG-biosynthetic enzymes led to reductions in their enzymatic activities as well as in the levels of GAGs. This review provides an overview of the growing number of glycobiological studies on recently characterized genetic disorders caused by the faulty biosynthesis of GAGs.

In carbohydrate chemistry, many useful stereoselective glycosylation methods have been developed that control the stereochemistry of the newly formed glycosylated product in chemical glycosylation. For example, in the past decade, unique stereoselective glycosylation methods have been reported that use glycosyl donors in which the ring is conformationally restricted by the di-tert-butylsilylene (DTBS) group as a cyclic silyl protecting group. To date, glycosyl donors with the DTBS group have been used to control the stereoselectivity of diverse chemical glycosylations for the formation of α-galactosides/galactosaminides, β-arabinofuranosides, α-sialosides, α-galactofuranosides, β-glucuronides, β-glucosides, β-mannosides, α-Kdo glycosides, and α-glucosides. Furthermore, the effect of ring-restriction for stereoselective glycosylations has provided new insights into the reaction mechanism of chemical glycosylation. This review provides a historical overview of stereoselective glycosylations using DTBS-tethered glycosyl donors and their application to the synthesis of biologically relevant carbohydrate molecules.

Glycans play a role in neural circuit formation and higher brain functions such as memory and learning in nervous system. Mucin-type O-glycans are present at high levels on mucins and T-cell immunoglobulin and mucin domains (TIM). Mucins are secreted from epithelial cells present in digestive organs. TIM possesses a T-cell immunoglobulin and mucin domain, and functions in the immune system. In addition, several mucin-type O-glycans are highly expressed in cancer cells and are thus used as a diagnostic marker. We previously found that T antigen, a mucin-type O-glycan, is highly expressed in the nervous system of Drosophila; however, the functions of mucin-type O-glycans in the nervous system remained largely unknown.

In this review, we describe the functions of mucin-type O-glycans in the nervous systems of mammals and invertebrates, focusing mainly on the role of T antigens in nervous system of Drosophila, which we have recently reported.