Globoside

Globosides are a sub-class of the lipid class glycosphingolipid[1] with three to nine sugar molecules as the side chain (or R group) of ceramide. The sugars are usually a combination of N-acetylgalactosamine, D-glucose or D-galactose. One characteristic of globosides is that the "core" sugars consists of Glucose-Galactose-Galactose (Ceramide-βGlc4-1βGal4-1αGal), like in the case of the most basic globoside Gb3, also known as pk-antigen. Another important characteristic of globosides is that they are neutral at pH 7, because they usually do not contain neuraminic acid, a sugar with an acidic carboxy-group. However, some globosides with the core structure Cer-Glc-Gal-Gal do contain neuraminic acid, e.g. the globo-series glycosphingolipid "SSEA-4-antigen"

N-Acetylgalactosamine
Sphingosine

The side chain can be cleaved by galactosidases and glucosidases. The deficiency of α-galactosidase A causes Fabry's disease, an inherited metabolic disease characterized by the accumulation of the globoside globotriaosylceramide.[2]

Globoside (GB4) has been known as the receptor for Parvovirus B19, due to observations that B19V binds to the thin-layered chromatogram of the structure. However, the binding on its surface does not match well with the virus, which raised debates on whether or not GB4 is the cause for productive infection.[3] Additional research using the technique Knockout Cell Line has shown that although GB4 does not have the direct entry receptor for B19V, it plays a post-entry role in productive infection.[4]

References
  1. Fahy, Eoin; Subramaniam, Shankar; Murphy, Robert C.; Nishijima, Masahiro; Raetz, Christian R.H.; Shimizu, Takao; Spener, Friedrich; van Meer, Gerrit; Wakelam, Michael J.O.; Dennis, Edward A. (April 2009). "Update of the LIPID MAPS comprehensive classification system for lipids". Journal of Lipid Research. 50 (Suppl): S9–S14. doi:10.1194/jlr.r800095-jlr200. ISSN 0022-2275. PMC 2674711. PMID 19098281.
  2. Germain, D. P. (2002). "Fabry's disease (alpha-galactosidase-A deficiency): Physiopathology, clinical signs, and genetic aspects". Journal de la Société de Biologie. 196 (2): 161–73. doi:10.1051/jbio/2002196020161. PMID 12360745.
  3. Nasir, Waqas; Nilsson, Jonas; Olofsson, Sigvard; Bally, Marta; Rydell, Gustaf E. (May 2014). "Parvovirus B19 VLP recognizes globoside in supported lipid bilayers". Virology. 456–457: 364–369. doi:10.1016/j.virol.2014.04.004. ISSN 1096-0341. PMID 24889255.
  4. Bieri, Jan; Ros, Carlos (15 October 2019). "Globoside Is Dispensable for Parvovirus B19 Entry but Essential at a Post-entry Step for Productive Infection". Journal of Virology. 93 (20). doi:10.1128/JVI.00972-19. ISSN 0022-538X. PMC 6798098. PMID 31341051.


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