Gi proteins use a novel beta gamma- and Ras-independent pathway to activate extracellular signal-regulated kinase and mobilize AP-1 transcription factors in Jurkat T lymphocytes.
Receptors coupled to pertussis toxin (PTX)-sensitive Gi proteins regulate T lymphocyte cytokine secretion, proliferation, and chemotaxis, yet little is known about the molecular mechanisms of Gi protein signaling in mammalian lymphocytes. Using the Jurkat T lymphocyte cell line, we found that a stably expressed Gi protein-coupled receptor (the delta-opioid receptor (DOR1)) stimulates MEK-1 and extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2) and transcriptional activity by an ERK target, Elk-1, via a mechanism requiring a PTX-sensitive Gi protein. Levels of beta-adrenergic receptor kinase-1 C-terminal fragment that inhibited signaling by Gi protein beta gamma subunits in these cells had no effect on DOR1 stimulation of either MEK-1- or Elk-1-dependent transcription, indicating that this pathway is independent of beta gamma. Analysis of this betagamma-independent pathway indicates a role for a herbimycin A-sensitive tyrosine kinase. Unlike beta gamma-mediated pathways, the beta gamma-independent pathway was insensitive to RasN17, inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase), and constitutive PI 3-kinase activity. The beta gamma-independent pathway regulates downstream events, since blocking it abrogated both Elk-1-dependent transcription and mobilization of the mitogenic transcription factor, AP-1, in response to DOR1 signaling. These results characterize a novel, Ras- and PI 3kinase-independent pathway for ERK activation by Gi protein signaling that is distinct from ERK activation by beta gamma and may therefore be mediated by the alphai subunit.
Department of Immunology, The Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA. hedin@mayo.edu
K E
KE
Hedin
M P
MP
Bell
C J
CJ
Huntoon
L M
LM
Karnitz
D J
DJ
McKean
D016227:Benzoquinones; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017465:Receptors, Opioid, delta / Q000378:metabolism; D017828:Rifabutin / Q000031:analogs & derivatives; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases; D050807:ets-Domain Protein Elk-1; D018631:ras Proteins / Q000378:metabolism*
D016227:Benzoquinones; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D004268:DNA-Binding Proteins; D019204:GTP-Binding Proteins; D047029:Lactams, Macrocyclic; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D011809:Quinones; D012333:RNA, Messenger; D017465:Receptors, Opioid, delta; D017828:Rifabutin; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D010566:Virulence Factors, Bordetella; D051552:beta-Adrenergic Receptor Kinases; D050807:ets-Domain Protein Elk-1; D018631:ras Proteins; C494112:ELK1 protein, human; C020754:herbimycin; C482125:MAP2K1 protein, human