Genetics and mammalian transport systems.
Membranes are organelles of homeostasis that control flux and distribution of molecules in cells. Carriers that mediate flux are gene products; mutations that modify carriers are probes that identify their function. Mutations can provide categorical taxonomies of membrane carriers; in higher organisms they can also identify location and characteristics of carriers. Mendelian human phenotypes reveal at least three different systems for the cationic amino acids (lys, orn, arg) segregated in brush-border (BBM) and basolateral (BLM) membranes of intestinal and renal epithelia; carrier(s) in parenchymal cells (e.g. fibroblasts) are not homologous. At least two gene products for phosphate reabsorption in nephron are revealed by X-linked and autosomal phenotypes; BBM and BLM also contain different forms of the carrier. Mutation reveals two forms of renal glucose reabsorption; the carriers are segregated in different proximal nephron segments. Mutations are potential probes for characterizing both the cellular pathways for synthesis, differentiation, insertion, segregation, turnover, and immobilization of membrane carrier proteins, and the mechanisms by which their function is altered.
D000042:Absorption; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003555:Cystinuria / Q000235:genetics / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000378:metabolism; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008661:Metabolism, Inborn Errors / Q000235:genetics* / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D008954:Models, Biological; D009005:Monosaccharides / Q000378:metabolism; D009154:Mutation; D009399:Nephrons / Q000378:metabolism; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism; D014960:X Chromosome
D000596:Amino Acids; D002352:Carrier Proteins; D009005:Monosaccharides; D010710:Phosphates; D005947:Glucose