Identification of tetratricopeptide repeat 1 as an adaptor protein that interacts with heterotrimeric G proteins and the small GTPase Ras.
The biological functions of heterotrimeric G proteins and small GTPases are modulated by both extracellular stimuli and intracellular regulatory proteins. Using Saccharomyces cerevisiae two-hybrid screening, we identified tetratricopeptide repeat 1 (TPR1), a 292-amino-acid protein with three TPR motifs, as a Galpha16-binding protein. The interaction was confirmed both in vitro and in transfected mammalian cells, where TPR1 also binds to several other Galpha proteins. TPR1 was found to interact with Ha-Ras preferentially in its active form. Overexpression of TPR1 promotes accumulation of active Ras. TPR1 was found to compete with the Ras-binding domain (RBD) of Raf-1 for binding to the active Ras, suggesting that it may also compete with Ras GTPase-activating protein, thus contributing to the accumulation of GTP-bound Ras. Expression of Galpha16 strongly enhances the interaction between TPR1 and Ras. Removal of the TPR1 N-terminal 112 residues abolishes potentiation by Galpha16 while maintaining the interaction with Galpha16 and the ability to discriminate active Ras from wild-type Ras. We have also observed that LGN, a Galphai-interacting protein with seven TPR motifs, binds Ha-Ras. Thus, TPR1 is a novel adaptor protein for Ras and selected Galpha proteins that may be involved in protein-protein interaction relating to G-protein signaling.
Marty
Caroline
C
Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
Browning
Darren D
DD
Ye
Richard D
RD
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000502:physiology; D020798:Two-Hybrid System Techniques; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; C102754:GPSM2 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; C475144:TTC1 protein, human; D019908:Proto-Oncogene Proteins c-raf; D020962:Heterotrimeric GTP-Binding Proteins; D018631:ras Proteins