Regulation of amino acid transport

From a physiological point of view, uptake systems make sense to a cell only when their substrates are both available in the medium and useful to the cell. As a matter of fact, the expression of the permease structural genes and the activity of the corresponding permeases are controlled and modulated by different types of regulatory systems. 

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Guidotti, G.G., Borghetti, A.S., Gazzola, G.C. (1978). The regulation of amino acid transport in animal cells. Biochim. Biophys. Acta 515, 329-366. 

Gazzola GC, Franchi R, Saibene V, Ronchi P, Guidotti GG. 1972. Regulation of amino acid transport in chick embryo heart cells. I. Adaptive system of mediation for neutral amino acids. Biochim Biophys Acta 266 407-421. 

Involvement of transporter recruitment as well as gene expression in the substrate-induced adaptive regulation of amino acid transport system A. Biochim Biophys... 

Some of the functions of glutathione depend on the presence of the gamma-glutamyl bond, for instance its role in the regulation of amino acid transport. But the majority of the functions of glutathione are related to its role in redox regulation in cells and in detoxification of xenobiotics. 

Characteristics and Hormonal Regulation of Amino Acid Transport System A in Isolated Rat Hepatocytes... 

Hormonal regulation of the System A activity in liver has been studied extensively. There are several reasons why isolated rat hepatocytes are a popular choice for investigations on the regulation of amino acid transport (1) the cells are isolated easily in high yield and viability (2) cells in... 

In this chapter, we shall focus on the molecular aspects of amino acid transport and its regulation in Saccharomyces cerevisiae. Kinetic, biochemical and genetic aspects of the amino acid transport systems of eukaryotic microorganisms have been reviewed earlier [7,8]. 

Rothstein A, Mack E (1991) Actions of mercurials on cell volume regulation of dissociated MDCK cells. Am J Physiol 260 C113-C121 Schaeffer JF, Preston RL, Curran PF (1973) Inhibition of amino acid transport in rabbit intestine by P-chloromercuriphenyl sulfonic acid. J Gen Physiol 672 131-146... 

The role of glucocorticoids in the regulation of System A activity in isolated hepatocytes has been studied in both cell suspensions and primary monolayer cultures. The inherent differences between these two cell populations with respect to a few of the characteristics of amino acid transport have been repeatedly documented (10, 25, 27, 28). Collectively, the investigations of glucocorticoid action on System A represent one of the best demonstrations that regulatory phenomena in hepatocytes should be tested using cells in suspension and in primary culture. T o illustrate this point and to explain some of the apparent contradictions in the data from different laboratories, the discussion of glucocorticoid action on System A will be presented in relation to the history or age of the hepatocytes. 

From a genetical point of view, Saccharomyces cerevisiae is an ideal organism which may be considered the Escherichia coli of eukaryotic cells [4,5]. This is true in particular for the study of metabolic regulation and for that of membrane transport [6]. Finally, the astonishing resemblance between many yeast proteins and certain mammalian-cell proteins has seriously broadened the scope of interest. Although a few reports have appeared on amino acid transport in some other yeasts, most investigations in this field have used strains of Saccharomyces cerevisiae. 

A rather satisfactory explanation of the irreversibility of amino acid accumulation in yeast cells is that it might result from specific regulatory mechanisms capable of immobilizing the transporters in a closed position. Uptake of amino acids by a number of permeases does indeed appear to be regulated by specific, and possibly allosteric, feedback inhibition. This idea is based on the fact that a number of transport systems seem to be specifically inhibited by their internally accumulated... 

To study the specific regulation of the synthesis of NCR-sensitive amino acid transporters, Saccharomyces cerevisiae cells are grown with proline or urea as the sole source of nitrogen, i.e., in the absence of NCR (see section 6.3). 

The regulation of NCR-sensitive amino acid transporters in Saccharomyces cerevisiae has many points in common with that of catabolic enzymes. Amino acid permeases, as well as some other transporters of nitrogenous nutrients, are integrated into the regulatory circuits, both general and specific, which control catabolic processes. 

Fig. 3. Synaptic localization of the mGluRs. The predominant localizations of the seven mGluR subtypes expressed in the CNS. The typical localizations of iGluRs and excitatory amino acid transporters (EAATs) are given, and the regulation of Glu release, iGluR signaling and ion channel activities mediated by the mGluRs is shown.

Excitatory amino acid transporters (EAATs) are the primary regulators of extracellular glutamate concentrations in the CNS. Glutamate clearance (and consequently glutamate concentration and diffusion in the extracellular space) is associated with the degree of astrocytic coverage of its neurons (Oliet et al. 

Boehmer C., Rajamanickam J., Schniepp R., Kohler K., Wulff P., Kuhl D., Palmada M., and Lang F. (2005). Regulation of the excitatory amino acid transporter EAAT5 by the serum and glucocorticoid dependent kinases SGK1 and SGK3. Biochem. Biophys. Res. Commun. 329 738-742. 

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