Glucose is a basic nutrient in most of the creatures; its transport through biological
membranes is an absolute requirement of life. This role is fulfilled by glucose transporters,
mediating the transport of glucose by facilitated diffusion or by secondary active
transport. GLUT (glucose transporter) or SLC2A (Solute carrier 2A) families represent
the main glucose transporters in mammalian cells, originally described as plasma membrane
transporters. Glucose transport through intracellular membranes has not been elucidated
yet; however, glucose is formed in the lumen of various organelles. The glucose-6-phosphatase
system catalyzing the last common step of gluconeogenesis and glycogenolysis generates
glucose within the lumen of the endoplasmic reticulum. Posttranslational processing
of the oligosaccharide moiety of glycoproteins also results in intraluminal glucose
formation in the endoplasmic reticulum (ER) and Golgi. Autophagic degradation of polysaccharides,
glycoproteins, and glycolipids leads to glucose accumulation in lysosomes. Despite
the obvious necessity, the mechanism of glucose transport and the molecular nature
of mediating proteins in the endomembranes have been hardly elucidated for the last
few years. However, recent studies revealed the intracellular localization and functional
features of some glucose transporters; the aim of the present paper was to summarize
the collected knowledge.
