The regulated exocytotic release of neurotransmitters in response to neural activity requires storage within intracellular vesicles. In the nervous system, these vesicles are the synaptic vesicles that are derived from the endosomal compartment, whereas in endocrine cells larger secretory granules, such as the chromaffin granules of adrenal medulla, are derived from the trans golgi networks. For classical transmitters that are synthesized in the cytoplasm or appear there after removal form the synapses by plasma membrane reuptake, storage depends upon the active transport into the vesicles. Several distinct transport activities have been identified for monoamines, acetylcholine, glutamate, GABA and glycine. Vesicular monoamine transporters (VMATs) catalyze transport and storage of monoamines, serotonin, dopamine, norepinephrine, epinephrine, and histamine. The driving force utilized by the VMAT is the H+ electrochemical gradient generated by a vacuolar ATP-dependent H+ pump (V-ATPase) located on vesicular plasma membrane. VMAT is inhibited by a wide variety of compounds including reserpine and tetrabenazine. In contrast to the plasma membrane transporters for dopamine, norepinephrine, and 5-HT which show relative substrate specificity, the monoamine transporter recognizes various monoamine with similar affinity. It was therefore speculated that either similar or identical transporters mediate the monoamine transport in all the tissues.

Recently, cDNA cloning by functional expression has identified two homologous but distinct VMAT genes from rat, bovine, and human adrenal glands. VMAT1 (previously termed CGAT for chromaffin granule amine transporter) is primarily expressed in adrenal glands, and it displays low sensitivity to inhibition by TBZ. It has about 3-fold lower affinity for most monoamines and about 100-fold less for histamine than the VMAT2. VMAT1 also has a lower turnover number than VMAT2. VMAT2, previously termed SVAT (synaptic vesicle amine transporter), is primarily found in monoaminergic cell bodies of the central nervous system and also in stomach but not in adrenals. Tetrabenazine and psychostimulants such as methamphetamine inhibits VMAT2 much more potently than VMAT1. Thus the VMATs show considerable differences in physiological and pharmacological properties. VMATs are predicted to contain 12 membrane spanning domains with a large hydrophilic loop and N-glycosylation sites between domain I and II. Both N and C-terminus are predicted to be cytoplasmic. Rat VMAT1 is a 521 aa transmembrane protein with 12 transmembrane domain (1). Rat VMAT2 is 515 aa.

A sodium-dependent transport system is responsible for transfer and distribution of vitamins to different parts of the body, the transfer includes vitamins like pantothenate, biotin, and ascorbic acid etc, These transporters belong to Solute Carrier family (SLC). Since vitamins are required for essential metabolic processes in all mammalian cells, such cells have developed intrinsic mechanisms to active accumulation of essential vitamins. Thus transporters help these cells to fulfill their requirement, they include Sodium-dependent Multi-Vitamin Transporter (SMVT), Sodium-dependent Vitamin-C Transporter (SVCT) 1 & 2, Creatine Transporter (CRT1/ CT1). The other vitamin transporters from SLC family include Thiamine Transporter Protein 1 (THTR1), Folate Transporter or Reduced Folate Carrier 1 (RFC1), Thyroid Iodide Transporter (TIT) and Taurine Transporter (TAU) etc.

Sodium-dependent Multi-Vitamin Transporter (SMVT), a 635aa protein in rat and human (gene SLC5A6) is responsible for transplacental transfer of vitamins pantothenate, biotin and the essential metabolite lipoate. SMVT shows homology to other known sodium-dependent nutrient transporters, including bacterial pantothenate permease, mammalian iodide transporter, glucose transporter 1 & 2. Quantitatively, the absorptive tissues like the intestinal mucosa, kidney and placenta have very high amounts of SMVT-specific mRNA. Significant amount is also seen in liver, brain, and heart.

Sodium-dependent Vitamin C Transporter (SVCT), Vitamin C is now known to mediate a variety of enzymatic reactions, including collagen synthesis, the basis for the defect in scurvy, the vitamin also protects tissues from oxidative damage by scavenging free radical. The vitamin C absorption and distribution requires SVCT1 and SVCT2.

SVCT1 605aa protein in rat, 604 in human (chrm 5, gene SLC23A1) contain up to 12 transmembrane domains, two possible sites for N-glycosylation and multiple phosphorylation sites. It is 65% identical to SVCT2 and largely expressed in epithelial surfaces involved in bulk transport such as intestine, liver and kidney.

SVCT2 account for tissue specific uptake of Vit C, expression is widespread occurring in neurons, bone and other tissues. SVCT2 is a 592aa protein in rat and 650aa long in human (chrm 20, gene SLC23A2). It is predominantly prenatal Vit C transporter to most tissues particularly in central nervous system and adrenal glands. Deficiency to this protein is lethal in newborn mice.

Creatine Transporter/ CRT1 or CT1 (mouse, human 635 aa, chromosome X28) is expressed in kidney, muscle, brain, and other tissues. A specific uptake system for creatine has been demonstrated in skeletal muscle, human monocytes, macrophages, and astroglial-rich cultures. Since muscle cells do not synthesize creatine, the creatine-phosphocreatine shuttle has important functions in the temporal and spatial maintenance of the energy supply to skeletal and cardiac muscle.

Thiamine Transporter Protein 1 (THTR1), a 498aa protein in mouse and 497 in human (chrm 1q23.3, gene SLC19A2) is a high affinity transporter for the intake of Thiamine, Most abundantly found in skeletal and cardiac muscle, lower levels are seen in placenta, heart, liver and kidney. Defects in gene are the cause of Thiamine Responsive Megaloblastic Anemia (TRMA)

Folate Transporter/ FOLT/ RFC, a 512aa each protein in mouse and rat, 591aa in human (chrm 21q22.3, gene SLC19A1) transports folate compounds into mammalian cells via receptor mediated or carrier mediated mechanisms, as such maintains the intracellular concentration of folate. It shows 65% identity to mouse and hamster folate transporters

Thyroid Iodide Transporter (TIT), a 618aa protein in rat with 12 transmembrane domains, with both N and C termini to be cytoplasmic. It transports Iodide at cellular level mediated by intrinsic membrane Na+/ I+ symporter, since iodide is an essential constituent of thyroid hormones.

Taurine Transporter (TAU), Taurine is a major intracellular amino acid in mammals involved in a number of important physiological processes. The Taurine transport is cells depend on Na+ & Cl- ions and is localized in basolateral plasma membrane. A 621aa protein in rat and 619aa in human (chrm 3p25.q24, gene SLC6A6) TAU regulates hypertonicity by intracellular accumulation of high concentrations of small organic solutes. Widely expressed in ileal, mucosa, brain, and liver.

 

Rb=rabbit; m=mouse; r=rat; h=human; b=bovine; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CP=Cytoplasmic domain; Control peptides (unconjugated, free, antigenic peptides), because of their small size, are not recommended for Western. They should be used in ELISA/antibody blocking studies.

"Neat Antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" antibodies have been over the antigen-affinity column and recommended for immunohistochemical applications.
"Control peptides" can not be used for Western as they are very short peptides. They are intended for ELISA or antibody competition studies.

 

List of Publications using ADI's antibodies for Transporters

TAU1, Takahashi K 2003 Biochemical Pharmacology Biochemical Pharmacology, Volume 65, Issue 7, 1 April 2003, Pages 1181-1187 Taurine transporter in primary cultured neonatal rat heart cells: a comparison between cardiac myocytes and nonmyocytes WB, cardiocytes in cullutre.

TAU1, Kang Y-S 2002 J. Neurochem. 83: 1188-1195. Regulation of taurine transport at the blood-brain barrier by tumor necrosis factor, taurine and hypertonicity WB, rat TR-BBB13 brain and kidney, 70 kda.

TAU1, Shioda R 2002 Invest. Opthalmol. Vis. Sci. 43, 2916-2922 Osmosensitive Taurine Transporter Expression and Activity in Human Corneal Epithelial Cells.

TAU11 Bridges CC et al 2002 Am J Physiol Cell Physiol 2001 281: C1825-C1836, Regulation of taurine transporter expression by NO in cultured human retinal pigment epithelial cells confocal microscopIHC, cultured human ARPE-19 cells and mouse retina.

TAU11 Olive, M. Foster 2000 European Journal of Neuroscience Volume 12, Issue 11, Page 4131 Reduced operant ethanol self-administration and in vivo mesolimbic dopamine responses to ethanol inPKC-deficient mice IHC, rat brain/dat from chemicon.

TIT Josefsson M 2002 Acta Physiologica Scandinavica 175 Issue 2 Page 129 Sodium/iodide-symporter: distribution in different mammals and role in entero-thyroid circulation of iodide.

NET Kantor L 2002 Eur J. Pharmacol. 451, 27-35 Enhanced amphetamine-mediated dopamine release develops in PC12 cells after repeated amphetamine treatment WB pC12 cells/SHYSy cells/82-kda

CRT Wang W et al 2002 Surgery. 132(2):334-340, Complement regulatory protein CD59 involves c-SRC related tyrosine phosphorylation of the creatine transporter in skeletal muscle during sepsis.

CRT Wang W et al 2002 Am J Physiol Endocrinol Metab, 285, 1046-1054 Cr supplementation decreases tyrosine phosphorylation of the CreaT in skeletal muscle during sepsis WB, IP, rat gastrocnemisu muscle.

VMAT2 human, Graff, Lothar 2001 Cancer Res. 2001 61: 2138-2144 Expression of Vesicular Monoamine Transporters, Synaptosomal-associated Protein 25 and Syntaxin1: A Signature of Human Small Cell Lung Carcinoma WB, Human Small Cell Lung Carcinoma.

VMAT2 Chen D 2000 Cell Tissue Res. 299, 81-95 effect of CCK-2 receptor blockade on rat stomach ECL cell WB, IHC, BP-128 made in g.pig.

VMAT2 Chen D 2000 Gastroenterology 2000 119: 756-765 Glycine-Extended Gastrin Synergizes With Gastrin 17 to Stimulate Acid Secretion in Gastrin-Deficient Mice IHC, mouse; stomach.

VGAT/VIAAT Redecker, Peter 2001 Neuroscience Letters, Volume 299, Issues 1-2, 16 February 2001, Pages 93-96 Evidence for microvesicular storage and release of glycine in rodent pinealocytes.

OAT-4 h Ugele B 2003 Am J Physiol Endocrinol Metab : 284, 390-398 CHARACTERIZATION AND IDENTIFICATION OF STEROID SULFATE TRANSPORTERS OF ISOLATED TROPHOBLASTS AND HUMAN PLACENTAL TISSUE IHC Paraffin sections/human term placenta.

OATP-C Nozawa A 2002 J. Pharmacol. Exp. Ther. 302: 804-813, Genetic Polymorphisms of Human Organic Anion Transporters OATP-C (SLC21A6) and OATP-B (SLC21A9): Allele Frequencies in the Japanese Population and Functional Analysis WB IHC human lymphocytes, HEk293 cells/formaldehyde fixed.

OATP2 Freeman, WM et al 2001 Neuroscience 108, 371-380 Cocaine-responsive gene expression changes in rat hippocampus WB, rat brain.