The TSC1 tumour suppressor hamartin regulates cell adhesion through ERM proteins and the GTPase Rho

Nat Cell Biol. 2000 May;2(5):281-7. doi: 10.1038/35010550.


Loss of the tumour-suppressor gene TSC1 is responsible for hamartoma development in tuberous sclerosis complex (TSC), which renders several organs susceptible to benign tumours. Hamartin, the protein encoded by TSC1, contains a coiled-coil domain and is expressed in most adult tissues, although its function is unknown. Here we show that hamartin interacts with the ezrin-radixin-moesin (ERM) family of actin-binding proteins. Inhibition of hamartin function in cells containing focal adhesions results in loss of adhesion to the cell substrate, whereas overexpression of hamartin in cells lacking focal adhesions results in activation of the small GTP-binding protein Rho, assembly of actin stress fibres and formation of focal adhesions. Interaction of endogenous hamartin with ERM-family proteins is required for activation of Rho by serum or by lysophosphatidic acid (LPA). Our data indicate that disruption of adhesion to the cell matrix through loss of hamartin may initiate the development of TSC hamartomas and that a Rho-mediated signalling pathway regulating cell adhesion may constitute a rate-limiting step in tumour formation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Actins / metabolism
  • Animals
  • Blood Proteins / metabolism*
  • Blood Proteins / pharmacology
  • Cell Adhesion / physiology
  • Cytoskeletal Proteins / metabolism*
  • Endothelium, Vascular / cytology*
  • Endothelium, Vascular / enzymology
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Genes, Tumor Suppressor / physiology
  • Humans
  • Lysophospholipids / pharmacology
  • Membrane Proteins / metabolism*
  • Mice
  • Microfilament Proteins / metabolism*
  • Peptide Fragments / pharmacology
  • Phosphoproteins / metabolism*
  • Proteins / metabolism*
  • Signal Transduction / physiology
  • Stress, Mechanical
  • Tuberous Sclerosis Complex 1 Protein
  • Tumor Suppressor Proteins
  • Two-Hybrid System Techniques
  • Umbilical Veins / cytology
  • rho GTP-Binding Proteins / metabolism*


  • Actins
  • Blood Proteins
  • Cytoskeletal Proteins
  • Lysophospholipids
  • Membrane Proteins
  • Microfilament Proteins
  • Peptide Fragments
  • Phosphoproteins
  • Proteins
  • TSC1 protein, human
  • Tsc1 protein, mouse
  • Tuberous Sclerosis Complex 1 Protein
  • Tumor Suppressor Proteins
  • ezrin
  • moesin
  • radixin
  • rho GTP-Binding Proteins