title: TSC2 modulates actin cytoskeleton and focal adhesion through TSC1-binding domain and the Rac1 GTPase.
abstract: Tuberous sclerosis complex (TSC) 1 and TSC2 are thought to be involved in protein translational regulation and cell growth, and loss of their function is a cause of TSC and lymphangioleiomyomatosis (LAM). However, TSC1 also activates Rho and regulates cell adhesion. We found that TSC2 modulates actin dynamics and cell adhesion and the TSC1-binding domain (TSC2-HBD) is essential for this function of TSC2. Expression of TSC2 or TSC2-HBD in TSC2-/- cells promoted Rac1 activation, inhibition of Rho, stress fiber disassembly, and focal adhesion remodeling. The down-regulation of TSC1 with TSC1 siRNA in TSC2-/- cells activated Rac1 and induced loss of stress fibers. Our data indicate that TSC1 inhibits Rac1 and TSC2 blocks this activity of TSC1. Because TSC1 and TSC2 regulate Rho and Rac1, whose activities are interconnected in a reciprocal fashion, loss of either TSC1 or TSC2 function may result in the deregulation of cell motility and adhesion, which are associated with the pathobiology of TSC and LAM.
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Goncharova
authors.forename: Dmitry
authors.initials: D
authors.lastname: Goncharov
authors.forename: Daniel
authors.initials: D
authors.lastname: Noonan
authors.forename: Vera P
authors.initials: VP
authors.lastname: Krymskaya
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D015536:Down-Regulation; D051379:Mice; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000199:Actins; D011506:Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; 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; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins