Role of Sialyl-O-Acetyltransferase CASD1 on GD2 Ganglioside O-Acetylation in Breast Cancer Cells

The O-acetylated form of GD2, almost exclusively expressed in cancerous tissues, is considered to be a promising therapeutic target for neuroectoderm-derived tumors, especially for breast cancer. Our recent data have shown that 9-O-acetylated GD2 (9-OAcGD2) is the major O-acetylated ganglioside species in breast cancer cells. In 2015, Baumann et al. proposed that Cas 1 domain containing 1 (CASD1), which is the only known human sialyl-O-acetyltransferase, plays a role in GD3 O-acetylation. However, the mechanisms of ganglioside O-acetylation remain poorly understood. The aim of this study was to determine the involvement of CASD1 in GD2 O-acetylation in breast cancer. The role of CASD1 in OAcGD2 synthesis was first demonstrated using wild type CHO and CHOΔCasd1 cells as cellular models. Overexpression using plasmid transfection and siRNA strategies was used to modulate CASD1 expression in SUM159PT breast cancer cell line. Our results showed that OAcGD2 expression was reduced in SUM159PT that was transiently depleted for CASD1 expression. Additionally, OAcGD2 expression was increased in SUM159PT cells transiently overexpressing CASD1. The modulation of CASD1 expression using transient transfection strategies provided interesting insights into the role of CASD1 in OAcGD2 and OAcGD3 biosynthesis, and it highlights the importance of further studies on O-acetylation mechanisms.

Research work undertaken in the Inokuchi Laboratory – Chronic inflammation & chronic disease research including diabetes and metabolic diseases.

Today, type 2 diabetes is typically treated by lowering sugar in the blood and increasing the sensitivity of muscle cells to insulin. However, novel discoveries could allow future treatments to target the molecular mechanisms in our bodies that generate insulin resistance – effectively preventing the biological chain of events that causes chronic inflammation and disease to initially occur. Professor Jin-ichi Inokuchi heads the Glycopathology Laboratory at Tohoku Medical and Pharmaceutical University, Japan. Situated within the Institute of Molecular Biomembrane and Glycobiology, the Laboratory focuses on gangliosides and their roles in inflammatory cycles. The scientists are particularly interested in GM3 ganglioside species, as their previous research has indicated that the increased presence of anti-inflammatory GM3 species and decreased presence of pro-inflammatory GM3 species have the power to alter inflammatory cycles in the body, thus contributing to chronic inflammation and associated diseases. Recently, Inokuchi and his colleagues' research revealed some interesting insights regarding GM3. Namely, they discovered that GM3 plays an important role in an inflammation amplification loop that affects diseases involving chronic inflammation, such as type 2 diabetes and metabolic diseases closely linked with obesity. 'Collectively, we propose a novel inflammation loop triggered by GM3 molecular species,' asserts Inokuchi. Inokuchi's research provides an avenue for tackling these conditions from the inside out. By focusing on the biological processes involved in these lifestyle-related chronic diseases, it may be possible to treat type 2 diabetes and metabolic diseases more efficiently.

O-acetylated Gangliosides as Targets for Cancer Immunotherapy

O-acetylation of sialic acid residues is one of the main modifications of gangliosides, and modulates ganglioside functions. O-acetylation of gangliosides is dependent on sialyl-O-acetyltransferases and sialyl-O-acetyl-esterase activities. CAS1 Domain-Containing Protein 1 (CASD1) is the only human sialyl-O-acetyltransferases (SOAT) described until now. O-acetylated ganglioside species are mainly expressed during embryonic development and in the central nervous system in healthy adults, but are re-expressed during cancer development and are considered as markers of cancers of neuroectodermal origin. However, the specific biological roles of O-acetylated gangliosides in developing and malignant tissues have not been extensively studied, mostly because of the requirement of specific approaches and tools for sample preparation and analysis. In this review, we summarize our current knowledge of ganglioside biosynthesis and expression in normal and pathological conditions, of ganglioside O-acetylation analysis and expression in cancers, and of the possible use of O-acetylated gangliosides as targets for cancer immunotherapy.

On-line nano-HPLC/ESI QTOF MS monitoring of α2–3 and α2–6 sialylation in granulocyte glycosphingolipidome

A novel glycosphingolipidomic protocol using nano-high performance liquid chromatography coupled on-line to electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS) focusing on the separation of isomeric ganglioside structures is described here. A highly efficient separation of α2–3- and α2–6-sialylated ganglioside species of different carbohydrate chain length was achieved on an HILIC-amido column, followed by sensitive flow-through ESI-QTOF-MS detection and unambiguous structural identification by tandem MS experiments. The protocol was applied to encompass the glycosphingolipidome of human granulocytes, where 182 distinct components could be clearly identified and assigned regarding the ganglioside type and the isomer distribution.