The pleckstrin homology domain mediates transformation by oncogenic dbl through specific intracellular targeting.
The pleckstrin homology (PH) domain is an approximately 100 amino acid structural motif found in many cellular signaling molecules, including the Dbl oncoprotein and related, putative guanine nucleotide exchange factors (GEFs). Here we have examined the role of the Dbl PH (dPH) domain in the activities of oncogenic Dbl. We report that the dPH domain is not involved in the interaction of Dbl with small GTP-binding proteins and is incapable of transforming NIH 3T3 fibroblasts. On the other hand, co-expression of the dPH domain with oncogenic Dbl inhibits Dbl-induced transformation. A deletion mutant of Dbl that lacks a significant portion of the PH domain retains full GEF activity, but is completely inactive in transformation assays. Replacement of the PH domain by the membrane-targeting sequence of Ras is not sufficient for the recovery of transforming activity. However, subcellular fractionations of Dbl and Dbl mutants revealed that the PH domain is necessary and sufficient for the association of Dbl with the Triton X-100-insoluble cytoskeletal components. Thus, our results suggest that the dPH domain mediates cellular transformation by targeting the Dbl protein to specific cytoskeletal locations to activate Rho-type small GTP-binding proteins.
Zheng
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Y
Department of Pharmacology, Cornell University, Ithaca, New York 14853-6401, USA.
Zangrilli
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D
Cerione
R A
RA
Eva
A
A
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D001798:Blood Proteins / Q000737:chemistry*; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; D051379:Mice; D009857:Oncogenes; D010750:Phosphoproteins; D011506:Proteins / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D013049:Spectrin / Q000378:metabolism; D051552:beta-Adrenergic Receptor Kinases; D020663:ras Guanine Nucleotide Exchange Factors
D001798:Blood Proteins; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; C512843:Mcf2 protein, mouse; D010750:Phosphoproteins; D011506:Proteins; D015682:Retroviridae Proteins, Oncogenic; C039077:platelet protein P47; D020663:ras Guanine Nucleotide Exchange Factors; D013049:Spectrin; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases