PT  - JOURNAL ARTICLE
AU  - Ekaitz Errasti-Murugarren
AU  - Francisco Javier Casado
AU  - Marcal Pastor-Anglada
TI  - DIFFERENT N-TERMINAL MOTIFS DETERMINE PLASMA MEMBRANE TARGETING OF hCNT3 IN POLARIZED AND NON-POLARIZED CELLS
AID  - 10.1124/mol.110.065920
DP  - 2010 Jan 01
TA  - Molecular Pharmacology
PG  - mol.110.065920
4099  - http://molpharm.aspetjournals.org/content/early/2010/07/19/mol.110.065920.short
4100  - http://molpharm.aspetjournals.org/content/early/2010/07/19/mol.110.065920.full
AB  - hCNT3 is a broad selectivity high affinity concentrative nucleoside transporter protein implicated in the uptake of most nucleoside-derived anticancer and antiviral drugs. Regulated trafficking of hCNT3 has been recently postulated as a suitable way to improve nucleoside-based therapies (Fernandez-Calotti and Pastor-Anglada, 2010). Moreover, the recent identification of a putative novel hCNT3-type transporter lacking the first 69 amino acids and retained at the endoplasmic reticulum anticipated that the N-terminus of hCNT3 contains critical motifs implicated in trafficking (Errasti-Murugarren et al., 2009). In this study we have addressed this issue by using deletions and site-directed mutagenesis and plasma membrane expression and nucleoside uptake kinetic analysis. Data reveal that: 1) a segment between amino acids 50-62 contains plasma membrane sorting determinants in non-polarized cells; 2) in particular, the Val57-Thr58-Val59 tripeptide appears to be the core of the export signal, whereas acidic motifs upstream and downstream of it seem to be important for the kinetics of the process; 3) in polarized epithelia the β-turn forming motif 17VGFQ20 is necessary for proper apical expression of the protein.