Amino acid transport regulation

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. 

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]. 

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.

Rothenberg ME, Doepker MP, Lewkowich IP, Chiaramonte MG, Stringer KF, Finkelman FD, MacLeod CL, Ellies LG, Zimmermann N (2006) Cationic amino acid transporter 2 regulates inflammatory homeostasis in the lung. Proc Natl Acad Sci USA 103(40) 14895-14900... 

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. 

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. 

Saier, M.H. Jr., Daniels, G.A., Boemer, P., Lin, J. (1988). Neutral amino acid transport systems in animal cells. Potential targets of oncogene action and regulators of cellular growth. J. Membr. Biol. 104,1-20. 

Shotwell, M.A., Kilberg, M.S., Oxender, D.L. (1983). The regulation of neutral amino acid transport in mammalian cells. Biochem. Biophys. Acta 737,267-284. 

Lee, W., tlaw kins, K., Peterson, D and Vina, J. R, (1996). Role of oxoproline in the regulation of neutral amino acid transport acros.s the blood-brain barrier. /. Biol. Chem. 271, 19129-19133. 

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