The PDZ protein TIP-1 interacts with the Rho effector rhotekin and is involved in Rho signaling to the serum response element.
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.
Laboratoire de Biologie Moléculaire et Cellulaire, Unité Mixte de Recherche 5665, CNRS-Ecole Normale Supérieure de Lyon, 46, Allée d'Italie, 69364 Lyon Cedex 07, France.
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D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002352:Carrier Proteins / Q000502:physiology*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000502:physiology; D004742:Enhancer Elements, Genetic; D019204:GTP-Binding Proteins; D005786:Gene Expression Regulation; D005972:Glutaminase; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D054461:Lim Kinases; D008969:Molecular Sequence Data; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D020218:Response Elements; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; C100494:RTKN protein, human; C498395:Rtkn protein, mouse; C421249:TAX1BP3 protein, human; D011494:Protein Kinases; C515892:LIMK1 protein, human; D054461:Lim Kinases; C515893:Limk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D005972:Glutaminase; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein