Heteromeric amino acid transporters: cystinuria and lysinuric protein intolerance

Abstract

Six families of plasma membrane amino acid transporters have been described in mammals, one of which has a heteromeric structure (Palacon et al. 1998; Chillaron et al. 2001). These heteromeric amino acid transporters (HATs) are composed of a heavy subunit and a ligh t subunit, linked by a disulfide bridge (Table 1, Figure 1). Two homologous heavy subunits (HSHATs) are known, rBAT (re lated to system bO,+ amino acid transport) and 4F2hc (heavy chain of the surface antigen 4F2, also referred to as CD98). Nine light subunits (LSHATs) have been identified. Six of them are partners of 4F2hc (LAT-l, LAT-2, y+LAT-l, y+LAT-2, asc-I, and xCT), one assembles with rBAT (bo,+AT), and two (asc-2 and AGT-l) seem to interact with as yet unknown heavy subunits (Kanai et al. 1998; Mastroberardi no et al. 1998; Torrents et al. 1998; Feliubadalo et al. 1999; Pineda et al. 1999; Rossier et al. 1999; Sato et al. 1999; Broer et al. 2000; Fukasawa et al. 2000; Chairoungdua et al. 2000; Matsuo et al. 2002).