title: Tuberin regulates E-cadherin localization: implications in epithelial-mesenchymal transition.
abstract: The tuberous sclerosis complex 2 (TSC2) gene encodes the protein tuberin, which functions as a key negative regulator of both mammalian target of rapamycin (mTOR) C1-dependent cell growth and proliferation. Loss-of-function mutations of TSC2 result in mTORC1 hyperactivity and predispose individuals to both tuberous sclerosis and lymphangioleiomyomatosis. These overlapping diseases have in common the abnormal proliferation of smooth muscle-like cells. Although the origin of these cells is unknown, accumulating evidence suggests that a metastatic mechanism may be involved, but the means by which the mTOR pathway contributes to this disease process remain poorly understood. In this study, we show that tuberin regulates the localization of E-cadherin via an Akt/mTORC1/CLIP170-dependent, rapamycin-sensitive pathway. Consequently, Tsc2(-/-) epithelial cells display a loss of plasma membrane E-cadherin that leads to reduced cell-cell adhesion. Under confluent conditions, these cells detach, grow in suspension, and undergo epithelial-mesenchymal transition (EMT) that is marked by reduced expression levels of both E-cadherin and occludin and increased expression levels of both Snail and smooth muscle actin. Functionally, the Tsc2(-/-) cells demonstrate anchorage-independent growth, cell scattering, and anoikis resistance. Human renal angiomyolipomas and lymphangioleiomyomatosis also express markers of EMT and exhibit an invasive phenotype that can be interpreted as consistent with EMT. Together, these results suggest a novel relationship between TSC2/mTORC1 and the E-cadherin pathways and implicate EMT in the pathogenesis of tuberous sclerosis complex-related diseases.
authors.affiliation: Department of Surgery, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Barnes
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Kenerson
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Jiang
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Yeung
mesh_terms: D018207:Angiomyolipoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D023102:Anoikis; D017209:Apoptosis; D015153:Blotting, Western; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007124:Immunoenzyme Techniques; D007680:Kidney Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018192:Lymphangioleiomyomatosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058570:TOR Serine-Threonine Kinases; D014402:Tuberous Sclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: D015820:Cadherins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins; D011506:Proteins; D012333:RNA, Messenger; C000624653:TSC2 protein, human; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C076744:cytoplasmic linker protein 170; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases
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