Lysinuric protein intolerance: mechanisms of pathophysiology.
Heteromeric amino acid transporters (HATs) are composed of two subunits, a polytopic membrane protein (the light subunit) and a disulfide-linked type II membrane glycoprotein (the heavy subunit). HATs represent several of the classic mammalian amino acid transport systems (e.g., L isoforms, y(+)L isoforms, asc, xc-, and b(0,+)). The light subunits confer the amino acid transport specificity to the HAT. Two transporters of this family are relevant for inherited aminoacidurias. Mutations in any of the two genes coding for the subunits of system b(0,+) (rBAT and b(0,+)AT) lead to cystinuria (MIM 220100). Transport defects in a system y(+)L isoform, composed of 4F2hc and y(+)LAT-1, result in lysinuric protein intolerance (LPI) (MIM 222700). In this case, only mutations in the light subunit y(+)LAT-1, but not in the heavy chain 4F2hc, cause the disease. LPI, in addition to affecting intestinal and renal reabsorption of amino acids, is a multisystemic disease affecting the urea cycle and presents also with symptoms related to the immune system. The pathogenesis of these alterations is less well, or not understood at all.
Palacín
Manuel
M
Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona and Parc Científic de Barcelona, Avenidda Diagonal 645, Barcelona 08028, Spain. mPalacin@bio.ub.es
Bertran
Joan
J
Chillarón
Josep
J
Estévez
Raúl
R
Zorzano
Antonio
A
D020157:Amino Acid Transport Disorders, Inborn / Q000235:genetics; D027241:Amino Acid Transport System y+L; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003555:Cystinuria / Q000235:genetics / Q000378:metabolism; D027301:Fusion Regulatory Protein 1, Light Chains / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008239:Lysine / Q000235:genetics / Q000378:metabolism* / Q000652:urine; D051379:Mice; D008958:Models, Molecular; D015394:Molecular Structure; D009154:Mutation; D010641:Phenotype; D014508:Urea / Q000378:metabolism
D027241:Amino Acid Transport System y+L; D026905:Amino Acid Transport Systems; D027301:Fusion Regulatory Protein 1, Light Chains; C421261:SLC7A7 protein, human; D014508:Urea; D008239:Lysine