期刊
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
卷 306, 期 1, 页码 156-162出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/S0006-291X(03)00921-5
关键词
glutamine transport; liver; amino acid transport; system N; pH; Na+; insulin
The amino acid transporter SN1 with substrate specificity identical to the amino acid transport system N is expressed mainly in astrocytes and hepatocytes where it accomplishes Na+-coupled glutamine uptake and efflux. To characterize properties and regulation of SN1, substrate-induced currents and/or radioactive glutamine uptake were determined in Xenopus oocytes injected with cRNA encoding SN1, the ubiquitin ligase Nedd4-2, and/or the constitutively active serum and glucocorticoid inducible kinase (S422D)SGK1, its isoform SGK3, and the constitutively active protein kinase B (T308D,S473D) PKB. The substrate-induced currents were enhanced by increasing glutamine and/or Na+ concentrations, hyperpolarization, and alkalinization (pH 8.0). They were inhibited by acidification (pH 6.0). Coexpression of Nedd4-2 downregulated SN1-mediated transport, an effect reversed by coexpression of (S422D)SGK1, SGK3, and T308D,S473D PKB. It is concluded that SN1 is a target for the ubiquitin ligase Nedd4-2, which is inactivated by the serum and glucocorticoid inducible kinase SGK1, its isoform SGK3, and protein kinase B. (C) 2003 Elsevier Science (USA). All rights reserved.
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