Regulatory pathways and uptake ofl-DOPA by capillary cerebral endothelial cells, astrocytes, and neuronal cells

2001 ◽  
Vol 280 (2) ◽  
pp. C333-C342 ◽  
Author(s):  
B. Sampaio-Maia ◽  
M. P. Serrão ◽  
P. Soares-da-Silva
Keyword(s):  
Amino Acid ◽  
Neuroblastoma Cells ◽  
Cell Types ◽  
Amino Acid Transporter ◽  
Nitric Oxide Donor ◽  
Intracellular Camp ◽  
Regulatory Pathways ◽  
Dopa Accumulation ◽  
Acid Transporter ◽  
Dopa Uptake

We examined the nature and regulation of the inwardl-3,4-dihydroxyphenylalanine (l-DOPA) transporter in rat capillary cerebral endothelial (RBE4) cells, type 1 astrocytes (DI TNC1), and Neuro-2a neuroblastoma cells. In all three cell types, the inward transfer of l-DOPA was largely promoted through the 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid-sensitive and sodium-independent L-type amino acid transporter. Only in DI TNC1 cells was the effect of maneuvers that increase intracellular cAMP levels accompanied by increases inl-DOPA uptake. Also, only in DI TNC1 cells was the effect of the guanylyl cyclase inhibitor LY-83583 accompanied by a 65% increase in l-DOPA accumulation, whereas the nitric oxide donor sodium nitroprusside produced a 25% decrease inl-DOPA accumulation. In all three cell types, the Ca2+/calmodulin inhibitors calmidazolium and trifluoperazine inhibited l-DOPA uptake in a noncompetitive manner. Thapsigargin (1 and 3 μM) and A-23187 (1 and 3 μM) failed to alter l-DOPA accumulation in RBE4 and Neuro-2a cells but markedly increased l-DOPA uptake in DI TNC1cells. We concluded that l-DOPA in RBE4, DI TNC1, and Neuro-2a cells is transported through the L-type amino acid transporter and appears to be under the control of Ca2+/calmodulin-mediated pathways. Astrocytes, however, are endowed with other processes that appear to regulate the accumulation of l-DOPA, responding positively to increases in intracellular Ca2+ and cAMP and to decreases in cGMP.

scholarly journals Amino Acid Transport Defects in Human Inherited Metabolic Disorders

2019 ◽  
Vol 21 (1) ◽  
pp. 119 ◽  
Author(s):  
Raquel Yahyaoui ◽  
Javier Pérez-Frías
Keyword(s):  
Amino Acid ◽  
Metabolic Disorders ◽  
Strong Association ◽  
Cell Types ◽  
Amino Acid Transporter ◽  
Molecular Defect ◽  
Amino Acid Transporters ◽  
Inherited Disorders ◽  
Laboratory Findings ◽  
Acid Transporter

Amino acid transporters play very important roles in nutrient uptake, neurotransmitter recycling, protein synthesis, gene expression, cell redox balance, cell signaling, and regulation of cell volume. With regard to transporters that are closely connected to metabolism, amino acid transporter-associated diseases are linked to metabolic disorders, particularly when they involve different organs, cell types, or cell compartments. To date, 65 different human solute carrier (SLC) families and more than 400 transporter genes have been identified, including 11 that are known to include amino acid transporters. This review intends to summarize and update all the conditions in which a strong association has been found between an amino acid transporter and an inherited metabolic disorder. Many of these inherited disorders have been identified in recent years. In this work, the physiological functions of amino acid transporters will be described by the inherited diseases that arise from transporter impairment. The pathogenesis, clinical phenotype, laboratory findings, diagnosis, genetics, and treatment of these disorders are also briefly described. Appropriate clinical and diagnostic characterization of the underlying molecular defect may give patients the opportunity to avail themselves of appropriate therapeutic options in the future.

scholarly journals Amino acid transporter B0AT1 influence on ADAM17 interactions with SARS-CoV-2 receptor ACE2 putatively expressed in intestine, kidney, and cardiomyocytes

2020 ◽  
Author(s):  
Jacob T. Andring ◽  
Robert McKenna ◽  
Bruce R. Stevens
Keyword(s):  
Amino Acid ◽  
Plasma Membranes ◽  
Renin Angiotensin System ◽  
Neck Region ◽  
Cell Types ◽  
Amino Acid Transporter ◽  
Common Denominator ◽  
Organ Systems ◽  
Acid Transporter

ABSTRACTSARS-CoV-2 exhibits significant experimental and clinical gastrointestinal, renal, and cardiac muscle tropisms responsible for local tissue-specific and systemic pathophysiology capriciously occurring in about half of COVID-19 patients. The underlying COVID-19 mechanisms engaged by these extra-pulmonary organ systems are largely unknown. We approached this knowledge gap by recognizing that neutral amino acid transporter B0AT1 (alternately called NBB, B, B0 in the literature) is a common denominator expressed nearly exclusively by three particular cell types: intestinal epithelia, renal proximal tubule epithelium, and cardiomyocytes. B0AT1 provides uptake of glutamine and tryptophan. The gut is the main depot expressing over 90% of the body’s entire pool of SARS-CoV-2 receptor angiotensin converting enzyme-2 (ACE2) and B0AT1. Recent cryo-EM studies established that ACE2 forms a thermodynamically favored dimer-of-heterodimers complex with B0AT1 assembled in the form of a dimer of two ACE2:B0AT1 heterodimers anchored in plasma membranes. Prior epithelial cell studies demonstrated ACE2 chaperone trafficking of B0AT1. This contrasts with monomeric expression of ACE2 in lung pneumocytes, in which B0AT1 is undetectable. The cell types in question also express a disintegrin and metalloproteinase-17 (ADAM17) known to cleave and shed the ectodomain of monomeric ACE2 from the cell surface, thereby relinquishing protection against unchecked renin-angiotensin-system (RAS) events of COVID-19. The present study employed molecular docking modeling to examine the interplaying assemblage of ACE2, ADAM17 and B0AT1. We report that in the monomer form of ACE2, neck region residues R652-N718 provide unimpeded access to ADAM17 active site pocket, but notably R708 and S709 remained >10-15 Å distant. In contrast, interference of ADAM17 docking to ACE2 in a dimer-of-heterodimers arrangement was directly correlated with the presence of a neighboring B0AT1 subunit complexed to the partnering ACE2 subunit of the 2ACE2:2B0AT1] dimer of heterodimers, representing the expression pattern putatively exclusive to intestinal, renal and cardiomyocyte cell types. The monomer and dimer-of-heterodimers docking models were not influenced by the presence of SARS-CoV-2 receptor binding domain (RBD) complexed to ACE2. The results collectively provide the underpinnings for understanding the role of B0AT1 involvement in COVID-19 and the role of ADAM17 steering ACE2 events in intestinal and renal epithelial cells and cardiomyocytes, with implications useful for consideration in pandemic public hygiene policy and drug development.

scholarly journals Comparison of Experimental Strategies to Study l-Type Amino Acid Transporter 1 (LAT1) Utilization by Ligands

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 37
Author(s):  
Johanna Huttunen ◽  
Mahmoud Agami ◽  
Janne Tampio ◽  
Ahmed B. Montaser ◽  
Kristiina M. Huttunen
Keyword(s):  
Amino Acid ◽  
Targeted Drug Delivery ◽  
Regular Function ◽  
Cell Types ◽  
Amino Acid Transporter ◽  
Acid Transporter ◽  
Comparison Of The Results ◽  
Kinetics Of ◽  
The Brain ◽  
Experimental Strategies

l-Type amino acid transporter 1 (LAT1), expressed abundantly in the brain and placenta and overexpressed in several cancer cell types, has gained a lot of interest in drug research and development, as it can be utilized for brain-targeted drug delivery, as well as inhibiting the essential amino acid supply to cancer cells. The structure of LAT1 is today very well-known and the interactions of ligands at the binding site of LAT1 can be modeled and explained. However, less is known of LAT1′s life cycle within the cells. Moreover, the functionality of LAT1 can be measured by several different methods, which may vary between the laboratories and make the comparison of the results challenging. In the present study, the usefulness of indirect cis-inhibition methods and direct cellular uptake methods and their variations to interpret the interactions of LAT1-ligands were evaluated. Moreover, this study also highlights the importance of understanding the intracellular kinetics of LAT1-ligands, and how they can affect the regular function of LAT1 in critical tissues, such as the brain. Hence, it is discussed herein how the selected methodology influences the outcome and created knowledge of LAT1-utilizing compounds.

scholarly journals ASC-1, PAT2, and P2RX5 are cell surface markers for white, beige, and brown adipocytes

2014 ◽  
Vol 6 (247) ◽  
pp. 247ra103-247ra103 ◽  
Author(s):  
Siegfried Ussar ◽  
Kevin Y. Lee ◽  
Simon N. Dankel ◽  
Jeremie Boucher ◽  
Max-Felix Haering ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cell Surface ◽  
Cell Types ◽  
Amino Acid Transporter ◽  
Specific Cell ◽  
Surface Markers ◽  
Cell Surface Markers ◽  
Brown Adipocytes ◽  
Beige Adipocytes ◽  
Acid Transporter

White, beige, and brown adipocytes are developmentally and functionally distinct but often occur mixed together within individual depots. To target white, beige, and brown adipocytes for diagnostic or therapeutic purposes, a better understanding of the cell surface properties of these cell types is essential. Using a combination of in silico, in vitro, and in vivo methods, we have identified three new cell surface markers of adipose cell types. The amino acid transporter ASC-1 is a white adipocyte–specific cell surface protein, with little or no expression in brown adipocytes, whereas the amino acid transporter PAT2 and the purinergic receptor P2RX5 are cell surface markers expressed in classical brown and beige adipocytes in mice. These markers also selectively mark brown/beige and white adipocytes in human tissue. Thus, ASC-1, PAT2, and P2RX5 are membrane surface proteins that may serve as tools to identify and target white and brown/beige adipocytes for therapeutic purposes.

Increased expression of an amino acid transporter LAT1 in healing of acetic acid-induced chronic gastric ulcer in rats

2001 ◽  
Vol 120 (5) ◽  
pp. A153-A153
Author(s):  
S MIYAMOTO ◽  
K KATO ◽  
Y ISHII ◽  
S ASAI ◽  
T NAGAISHI ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Gastric Ulcer ◽  
Amino Acid ◽  
Amino Acid Transporter ◽  
Chronic Gastric Ulcer ◽  
Acid Transporter

scholarly journals Identification and Characterization of Inhibitors of a Neutral Amino Acid Transporter, SLC6A19, Using Two Functional Cell-Based Assays

2018 ◽  
Vol 24 (2) ◽  
pp. 111-120 ◽  
Author(s):  
Sanjay J. Danthi ◽  
Beirong Liang ◽  
Oanh Smicker ◽  
Benjamin Coupland ◽  
Jill Gregory ◽  
...  
Keyword(s):  
Amino Acid ◽  
High Throughput Screening ◽  
Amino Acid Transporter ◽  
Neutral Amino Acid ◽  
Imaging Plate ◽  
Acid Uptake ◽  
Functional Assays ◽  
Neutral Amino Acid Transporter ◽  
Acid Transporter ◽  
Pharmacologically Active

SLC6A19 (B0AT1) is a neutral amino acid transporter, the loss of function of which results in Hartnup disease. SLC6A19 is also believed to have an important role in amino acid homeostasis, diabetes, and weight control. A small-molecule inhibitor of human SLC6A19 (hSLC6A19) was identified using two functional cell-based assays: a fluorescence imaging plate reader (FLIPR) membrane potential (FMP) assay and a stable isotope-labeled neutral amino acid uptake assay. A diverse collection of 3440 pharmacologically active compounds from the Microsource Spectrum and Tocriscreen collections were tested at 10 µM in both assays using MDCK cells stably expressing hSLC6A19 and its obligatory subunit, TMEM27. Compounds that inhibited SLC6A19 activity in both assays were further confirmed for activity and selectivity and characterized for potency in functional assays against hSLC6A19 and related transporters. A single compound, cinromide, was found to robustly, selectively, and reproducibly inhibit SLC6A19 in all functional assays. Structurally related analogs of cinromide were tested to demonstrate structure–activity relationship (SAR). The assays described here are suitable for carrying out high-throughput screening campaigns to identify modulators of SLC6A19.

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