6– 8 They are subdivided into three classes based on their protein sequence and structural similarity. 4, 5 They are encoded by the solute linked carrier family 2, subfamily A gene family, SLC2A, and the original name glucose transporter is somewhat misleading as many have substrates other than hexoses. There are 14 mammalian facilitative glucose transporters ( Table 1), and they belong to the sugar porter family in the major facilitator superfamily (MFS). 2, 3 In contrast, GLUTs are passive transporters that use either chemical or electrochemical gradients to transport hexoses or other substrates. The first is the sodium/glucose co-transporters (SGLTs), which are secondary active transporters that use the sodium gradient across the cell membrane to drive glucose and galactose uptake. 1 There are now known to be at least two distinct transporter gene families responsible for the handling of hexoses in mammalian cells. Hexoses are an essential carbon and energy source for the cells of the human body, and their entry and exit across the plasma membrane is critical for life. Keywords: GLUT proteins, Facilitated hexose transporters, protein trafficking, cancer imaging, genetic diseases Finally, as we better understand how GLUTs bind and transport their substrates, it may be possible to design drugs that can be delivered into target cells for the treatment of a number of diseases.

Determination of alterations in expression patterns may prove to be a useful diagnostic tool, and in some cases these are already being taken advantage of for the imaging of cancers. It has long been known that GLUT1 expression increases significantly in cancer cells, but it is now becoming appreciated that other GLUTs may also be involved. Another promising area of investigation is the changes in expression levels of GLUTs associated with, and likely in consequence of, disease processes. Genetic diseases associated with GLUTs are very rare, emphasizing their critical roles, but it is likely that as our understanding of these transporters increases, there may be more clinical conditions found to be associated with subtle changes in their activity. However, the other two classes have received far less attention. The physiological roles of Class I GLUTs, ie, 1, 2, 3 (14), and 4 have been extensively studied for their contributions to metabolism and development. The GLUT family is divided into three classes based on their sequence homology. Despite over five decades of research, it is still not fully understood how they work at the molecular level, although the recent publication of a crystal structure of GLUT1 suggests this may be resolved soon.

These proteins are essential for moving the key metabolites, glucose, galactose, and fructose in and out of cells, as well as a number of other important substrates. Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, CanadaĪbstract: This review examines the development of structure and function of the human GLUT proteins, gene family hSLC2A.

Glut 1 2 3 4