. 2021 Aug 20;13(16):4184. doi: 10.3390/cancers13164184

Table 2.

Characteristics of the human sodium-dependent symporters [1].

Gene	Protein	Localization and Characteristics
SLC5A1 22q12.3	SGLT1 It is composed of 664 (662) amino acids with a molecular weight of 73 kDa.	It is expressed in the mature enterocytes of brush border membrane in the small intestine, trachea, prostate, heart, and kidneys and in the luminal membrane of intracerebral capillary endothelial cells. SGLT1 mRNA is detected in the human prostate, testis, trachea, and uterus (cervix). SGLT1 is a high-affinity, low-capacity transporter for D-glucose and D-galactose. It does not transport fructose, mannose, and xylose. It may also behave as the glucose receptor in the heart and brain.
SLC5A2 16p11.2	SGLT2 It is composed of 672 amino acids with a predicted mass of 73 kDa.	It is expressed on the apical membrane of renal convoluted proximal tubules. SGLT2 mRNA was detected in the mammary glands, liver, lungs, intestine, skeletal muscle, and spleen. It is suggested that SGLT2 may also behave as the glucose receptor in the heart and brain. SGLT2 represents a low-affinity, high-capacity sodium-glucose symporter for glucose.
SLC5A3 21q22.11 Splicing within and distal to exon 2, leads to 3 transcripts namely SMIT1, SMIT2 and SMIT3.	SMIT1	It is expressed in the kidneys, brain, placenta, pancreas, heart, skeletal muscle, and the lungs. Its mRNA was detected in the blood vessels (choroid plexus and coronary artery, intestine, ovary, pineal gland, prostate, thyroid gland, and uterus (cervix). It transports myo-inositol, L-fucose, and L-xylose (but not their D-isomers) and does not distinguish between D- and L-glucose.
SLC5A4 22q12.3.	SGLT3 (SAAT1) It is composed of 659 amino acids.	It is expressed in the kidneys, uterus, testis, intestinal autonomic nervous, skeletal muscle, brain, proximal tubule of human kidneys and in the cholinergic neurons in the enteric nervous system, and its mRNA is detected in the pancreas, lungs, and liver. SGLT3 demonstrates a lack of sugar transport activity. It does not transport glucose, but it is a glucose sensor.
SLC5A5 19p13.11.	NIS	It is a Na⁺/iodide cotransporter. It is principally expressed in the thyroid, where it is responsible for the accumulation of iodide necessary for thyroid hormones T₃ and T₄. NIS is also expressed in the lactating breast, colon, stomach, and ovary. The substrate specificities for NIS are I⁻ (ClO₄⁻, SCN⁻, NO₃⁻, Br⁻).
SLC5A6 2q12.	SMVT	It is a multivitamin Na⁺ cotransporter. It is expressed in the brain, heart, kidneys, lungs, and placenta. It mediates Na⁺-dependent uptake of vitamins such as pantothenic acid, biotin, and α-lipoic acid. Because SMVT has a high sequence identity and similarity with NIS, it also behaves as a Na⁺/iodide cotransporter
SLC5A7 2q13.	CHT1	It is a Cl⁻–dependent Na⁺/choline cotransporter that is expressed in the central nervous system in the spinal cord and medulla and transport is sensitive to pH.
SLC5A8 12q23.1.	SMCT1	It is expressed in the small intestine, kidneys, brain, retina, and muscle. It is a monocarboxylate cotransporter which transports lactate, pyruvate, and nicotinate with a stoichiometry of 2:1.
SLC5A9 1p32.	SGLT4	It is expressed in the small intestine, kidneys, brain, liver, heart, uterus, and lungs. SGLT4 mRNA, at low levels, was also detected in the testis, pancreas, and skeletal muscle. It is involved in absorption and/or the reabsorption of D-mannose, D-fructose, and D-glucose.
SLC5A10 17p11.2 There are four splice variants.	SGLT5	It is expressed in the human kidney cortex. SGLT5 mRNA was detected also in the left atrium of the heart, ovary, skin (foreskin), testis, and in vas deferens. SGLT5 has been reported to be a sodium-dependent sugar transporter with a relatively high affinity and capacity for mannose and fructose relative to glucose and galactose.
SLC5A11 16p12.1.	SGLT6 (now known as SMIT2).	It is detected in the brain, heart, kidneys, skeletal muscle, spleen, liver, placenta, lungs, leukocytes, and neurons. SGLT6 transports myo-inositol and d-chiro-inositol. It shows stereoscopic transport of D-glucose and D-xylose without affinity for fructose. In humans, SLC5A11 interacts with immune-related gene(s) and may function as an autoimmune modifier gene.
SLC5A12 11p14.2.	SMCT2.	It is expressed in the small intestine, kidneys, brain, retina, and muscle. It is a monocarboxylate cotransporter that transports lactate, pyruvate, and nicotinate with a stoichiometry of 2:1.