Abstract
Gangliosides are constituents of the mammalian cell membranes and participate in the inflammatory response. However, little is known about the presence and enzymatic activity of ganglioside sialyltransferases at the cell surface of macrophages, one of the most important immune cells involved in the innate inflammatory process. In the present study, using biochemical and fluorescent microscopy approaches, we found that endogenous ST8Sia-I is present at the plasma membrane (ecto-ST8Sia-I) of murine macrophage RAW264.7 cells. Moreover, ecto-ST8Sia-I can synthetize GD3 ganglioside at the cell surface in lipopolysaccharide (LPS)-stimulated macrophages even when LPS-stimulated macrophages reduced the total ST8Sia-I expression levels. Besides, cotreatment of LPS with an inhibitor of nitric oxide (NO) synthase recovered the ecto-ST8Sia-I expression, suggesting that NO production is involved in the reduction of ST8Sia-I expression. The diminution of ST8Sia-I expression in LPS-stimulated macrophages correlated with a reduction of GD3 and GM1 gangliosides and with an increment of GD1a. Taken together, the data supports the presence and activity of sialyltransferases at the plasma membrane of RAW264.7 cells. The variations of ecto-ST8Sia-I and ganglioside levels in stimulated macrophages constitutes a promissory pathway to further explore the physiological role of this and others ganglioside metabolism-related enzymes at the cell surface during the immune response.
Highlights
Gangliosides are sialic acid-containing glycosphingolipids that are constituents of mammalian cell membranes
In addition to the presence of glycohydrolases and sialidases associated with the outer layer of the plasma membrane, we demonstrated in epithelial and melanoma cells that sialyltransferase ST8Sia-I is able to sialylate GM3 ganglioside exposed on cell surface itself or exposed at the plasma membrane of neighboring cells [22,23]
To the best of our knowledge, this is the first report that shows the presence of ecto-ST8-I at the plasma membrane of macrophages, besides its classical localization at the Golgi complex
Summary
Gangliosides are sialic acid-containing glycosphingolipids that are constituents of mammalian cell membranes. They are mainly located in the outer layer of the plasma membrane of vertebrate cells [1,2]. A recent report provides evidence of the role of GD3 synthase (ST8Sia-I) in bone metabolism in animals and suggests that altered ganglioside metabolism is associated with this bone loss during aging [7]. In melanoma cells, specific gangliosides are associated with the adapter molecules of the cell surface promoting their activation during adhesion [9,10]. The enzymatic changes underlying ganglioside modification remain largely unknown
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
