Intersectin activates Ras but stimulates transcription through an independent pathway involving JNK.
Intersectin (ITSN) is a molecular scaffold involved in regulating endocytosis and mitogenic signaling. We previously demonstrated that ITSN transformed rodent fibroblasts, accelerated hormone-induced maturation of Xenopus oocytes, and activated the Elk-1 transcription factor through an MEK- and Erk-independent mechanism. We now demonstrate that ITSN complexes with the Ras guanine nucleotide exchange factor Sos1 leading to increased RasGTP levels. Using fluorescence resonant energy transfer analysis, we demonstrate that ITSN complexes with Ras in living cells leading to Ras activation on intracellular vesicles. These vesicles contain epidermal growth factor receptor but are distinct from transferrin-positive vesicles. However, Ras is not required for ITSN stimulation of transcription. Rather, we demonstrate that ITSN signals through JNK to activate Elk-1. Although ITSN activation of Elk-1 was Ras-independent, ITSN cooperates with Ras to synergistically activate JNK. These findings indicate that ITSN activates multiple intracellular signaling pathways and suggest that this adaptor protein may coordinately regulate the activity of these pathways in vivo.
Mohney
Robert P
RP
Laboratory of Signal Transduction, National Institute of Environmental Health Services, NIH/DHHS, Building 101, Research Triangle Park, NC 27709, USA.
Das
Margaret
M
Bivona
Trever G
TG
Hanes
Richard
R
Adams
Anthony G
AG
Philips
Mark R
MR
O'Bryan
John P
JP
D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins; D015398:Signal Transduction; D014157:Transcription Factors; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D050807:ets-Domain Protein Elk-1; D018631:ras Proteins / Q000378:metabolism*
D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; C494113:Elk1 protein, mouse; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D050807:ets-Domain Protein Elk-1; C115919:intersectin 1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins