Transport of Sugars

Abstract

Soluble sugars serve five main purposes in multicellular organisms: as sources of carbon skeletons, osmolytes, signals, and transient energy storage and as transport molecules. Most sugars are derived from photosynthetic organisms, particularly plants. In multicellular organisms, some cells specialize in providing sugars to other cells (e.g., intestinal and liver cells in animals, photosynthetic cells in plants), whereas others depend completely on an external supply (e.g., brain cells, roots and seeds). This cellular exchange of sugars requires transport proteins to mediate uptake or release from cells or subcellular compartments. Thus, not surprisingly, sugar transport is critical for plants, animals, and humans. At present, three classes of eukaryotic sugar transporters have been characterized, namely the glucose transporters (GLUTs), sodium-glucose symporters (SGLTs), and SWEETs. This review presents the history and state of the art of sugar transporter research, covering genetics, biochemistry, and physiology-from their identification and characterization to their structure, function, and physiology. In humans, understanding sugar transport has therapeutic importance (e.g., addressing diabetes or limiting access of cancer cells to sugars), and in plants, these transporters are critical for crop yield and pathogen susceptibility.

Transcriptome Profiling of Tiller Buds Provides New Insights into PhyB Regulation of Tillering and Indeterminate Growth in Sorghum

“…MtN3 encodes a SWEET transporter, a member of a family of Suc/sugar transporters that are involved in phloem sugar loading/unloading and efflux of sugars from maternal tissues for seed filling and pollen development (Chen et al, 2012;Guo et al, 2014;Chen et al, 2015). CwINVs cleave apoplastic Suc into Glc and Fru for import into cells (Sherson et al, 2003;Weschke et al, 2003).…”

D-Allose Inhibits Cancer Cell Growth by Reducing GLUT1 Expression

“…So far, 14 GLUTs have been found in humans and include transporters for fructose, urate, and myoinositol (Chen et al 2015). Of those, GLUT1 is involved in the facilitated diffusion of glucose into cells and maintains basal glucose transport in most types of cells.…”

Dysfunction of the Cerebral Glucose Transporter SLC45A1 in Individuals with Intellectual Disability and Epilepsy

“…However, its availability is restricted given the selective permeability of the blood brain barrier (BBB) and the relative lack of carbohydrate stores in the brain. Thus, glucose transport across the BBB and into neural cells is critical for cerebral physiologic function and energy metabolism (for a review, see Chen et al 1 ). GLUT1 is the key regulator of glucose across the BBB.…”

“…GLUT1 is the key regulator of glucose across the BBB. 1 The importance of this process is illustrated by the observation that dominant mutations in SLC2A1 (OMIM: 138140), which encodes GLUT1, cause epilepsy with variable degrees of intellectual disability (ID) and/or movement disorder. 2 Once glucose enters the brain's extracellular space, it is taken up by different cerebral cells through various glucose transporters, which are expressed in developmentally and celltype-specific manners.…”