Similarities and differences in the subcellular localization of hamartin and tuberin in the kidney.
Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by hamartomas in multiple organs, notably the brain and kidneys. The disease is caused by mutations in TSC1 or TSC2 genes, coding hamartin and tuberin, respectively. Immunofluorescence analysis of tuberin and hamartin performed here demonstrates that both proteins are specifically expressed in the distal urinary tubule, comprising the distal tubules, connecting segment, and collecting ducts. Hamartin, distinct from tuberin, is expressed in the thick ascending limbs of Henle and in juxtaglomerular cells, where it colocalizes with renin. In positive epithelial cells, tuberin localizes to the cytoplasm as well as the apical membrane. Hamartin, however, preferentially localizes to the apical membrane. The two proteins colocalize at the apical membrane of type A intercalated cells and connecting tubule cells, whereas in type B intercalated cells they reveal a variable pattern of expression. The cell-specific expression of tuberin and hamartin described here will provide critical insight into the cell types that give rise to kidney lesions, and the tumor suppressor role of these proteins in TSC.
Murthy
V
V
Molecular Neurogenetics Unit, Charlestown, Massachusetts 02129, USA.
Haddad
L A
LA
Smith
N
N
Pinney
D
D
Tyszkowski
R
R
Brown
D
D
Ramesh
V
V
D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal; D019556:COS Cells; D002460:Cell Line; D006367:HeLa Cells; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D051379:Mice; D009154:Mutation; D011506:Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D014402:Tuberous Sclerosis / Q000235:genetics / Q000378:metabolism; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins
D000911:Antibodies, Monoclonal; D011506:Proteins; D012097:Repressor Proteins; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; C000624651:Tsc1 protein, mouse; C000624652:Tsc1 protein, rat; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins