Isolation and function of the amino acid transporter PAT1 (slc36a1) from rabbit and discrimination between transport via PAT1 and system IMINO in renal brush-border membrane vesicles

Abstract

Reabsorption of amino acids is an important function of the renal proximal tubule. pH-dependent amino acid transport has been measured previously using rabbit renal brush-border membrane vesicles (BBMV). The purpose of this investigation was to determine whether this pH-dependent uptake represents H(+)/amino acid cotransport via a PAT1-like transport system. The rabbit PAT1 cDNA was isolated (2296bp including both 5' and 3' untranslated regions and poly(A) tail) and the open reading frame codes for a protein of 475 amino acids (92% identity to human PAT1). Rabbit PAT1 mRNA was found in all tissues investigated including kidney. When expressed heterologously in a mammalian cell line, rabbit PAT1 mediates pH-dependent, Na(+)-independent uptake of proline, glycine, l-alanine and alpha-(methylamino)isobutyric acid. Proline uptake was maximal at pH 5.0 (K(m) 2.2+/-0.7 mM). A transport system with identical characteristics (ion dependency, substrate specificity) was detected in rabbit renal BBMV where an overshoot was observed in the absence of Na+ but in the presence of an inwardly directed H+ gradient. In the presence of Na+ and under conditions in which PAT1 transport function was suppressed, a second proline uptake system was detected that exhibited functional characteristics similar to those of the IMINO system. The functional characteristics of rabbit PAT1 in either mammalian cells or renal BBMV suggest that PAT1 is the low-affinity transporter of proline, glycine and hydroxyproline believed to be defective in patients with iminoglycinuria.

The Molecular Mechanism of Intestinal Levodopa Absorption and Its Possible Implications for the Treatment of Parkinson’s Disease

“…B 0 AT1-ACE2 (SLC6A19) transports AAs with close structural homology to levodopa (Phe and Tyr). The IMINO transporter SIT1 (SLC6A20) and the proton-dependent AA transporter PAT1 (SLC36A1) transport neutral AAs to some extent (Miyauchi et al, 2005;Ristic et al, 2006). The AA exchanger ASCT2 (SLC1A5) transports neutral AAs and has been suggested to be localized apically in rabbits (Avissar et al, 2001) and basolaterally in mouse enterocytes (Broer et al, 2011).…”

Proton-dependent glutamine uptake by aphid bacteriocyte amino acid transporter ApGLNT1

“…These results demonstrate that ApGLNT1 is specific for glu-297 tamine, and that extracellular glutamine induces net inward movement 298 of positive charge. 299 In comparison to ApGLNT1, related mammalian AAAP transporters 300 PAT1 and PAT2 have a different and broader substrate selectivity, with 301 both mammalian transporters mediating electrogenic, H + -dependent 302uptake of glycine N alanine N proline[29][30][31][32][33]. In mammals, PAT1 (K m 303 2.8-7.5 mM) is highly expressed in the small intestine, kidney, brain 304…”

“…4a and b). Glutamine and colon [29][30][31][32], whereas PAT2 (K m 0.1-0.6 mM) is predominantly 305 expressed in heart and lung tissues [30,33].…”

Hijacking Solute Carriers for Proton-Coupled Drug Transport

“…Many other H ϩ -coupled transporters are expressed in specific sections of the proximal tubule including the amino acid/ drug transporter PAT1 (see above) (70,107), the related PAT2 (SLC36A2) ( Table 1) (120), and the nicotinate transporter OAT10 (see above) (9). These transporters, and others, may significantly influence the systemic exposure to certain drug substrates.…”