The PDZ protein TIP-1 interacts with the Rho effector rhotekin and is involved in Rho signaling to the serum response element

J Biol Chem. 2000 Oct 27;275(43):33962-8. doi: 10.1074/jbc.M000465200.


The human T-cell lymphotrophic virus, type 1 Tax protein can interact via its C terminus with various proteins including a PDZ domain. In this work, one of them, TIP-1, is characterized as a cytoplasmic 14-kDa protein mainly corresponding to one PDZ domain. A two-hybrid screen performed with TIP-1 as bait showed that it interacts with the human homologue of rhotekin that was previously identified in mice as a Rho effector. Both human and mouse rhotekins exhibit at their C termini the sequence QSPV-COOH that matches the X(S/T)XV-COOH consensus known for proteins recognizing PDZ domains. Mutation of the serine and valine residues to alanine impairs interaction of rhotekin with TIP-1. Transient expression experiments with a reporter construct including the c-Fos serum response element (SRE) showed that coexpression of TIP-1 with the constitutively active RhoA.V14 mutant and human rhotekin caused a strong activation of the SRE. A negative mutant of Rho, RhoA.N19, was unable to cooperate with TIP-1 and rhotekin. The positive effect of TIP-1 was also lost when the C terminus of rhotekin was mutated. These data show that the complex of active Rho with its effector rhotekin bound to TIP-1 produces in the cytoplasm a signal that triggers strong activation of the SRE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Carrier Proteins / physiology*
  • Cloning, Molecular
  • DNA-Binding Proteins / physiology
  • Enhancer Elements, Genetic
  • GTP-Binding Proteins
  • Gene Expression Regulation
  • Glutaminase*
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins*
  • Lim Kinases
  • Molecular Sequence Data
  • Protein Kinases
  • Protein-Serine-Threonine Kinases / physiology
  • Proteins / genetics
  • Proteins / physiology*
  • Response Elements*
  • rhoA GTP-Binding Protein / physiology*


  • Carrier Proteins
  • DNA-Binding Proteins
  • Intracellular Signaling Peptides and Proteins
  • Proteins
  • RTKN protein, human
  • Rtkn protein, mouse
  • TAX1BP3 protein, human
  • Protein Kinases
  • LIMK1 protein, human
  • Lim Kinases
  • Limk1 protein, mouse
  • Protein-Serine-Threonine Kinases
  • Glutaminase
  • GTP-Binding Proteins
  • rhoA GTP-Binding Protein