Transactivation of Trk neurotrophin receptors by G-protein-coupled receptor ligands occurs on intracellular membranes.
Neurotrophins, such as NGF and BDNF, activate Trk receptor tyrosine kinases through receptor dimerization at the cell surface followed by autophosphorylation and intracellular signaling. It has been shown that activation of Trk receptor tyrosine kinases can also occur via a G-protein-coupled receptor (GPCR) mechanism, without involvement of neurotrophins. Two GPCR ligands, adenosine and pituitary adenylate cyclase-activating polypeptide (PACAP), can activate Trk receptor activity to increase the survival of neural cells through stimulation of Akt activity. To investigate the mechanism of Trk receptor transactivation, we have examined the localization of Trk receptors in PC12 cells and primary neurons after treatment with adenosine agonists and PACAP. In contrast to neurotrophin treatment, Trk receptors were sensitive to transcriptional and translational inhibitors, and they were found predominantly in intracellular locations particularly associated with Golgi membranes. Biotinylation and immunostaining experiments confirm that most of the transactivated Trk receptors are found in intracellular membranes. These results indicate that there are alternative modes of activating Trk receptor tyrosine kinases in the absence of neurotrophin binding at the cell surface and that receptor signaling may occur and persist inside of neuronal cells.
Rajagopal
Rithwick
R
Molecular Neurobiology Program, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA.
Chen
Zhe-Yu
ZY
Lee
Francis S
FS
Chao
Moses V
MV
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006056:Golgi Apparatus / Q000201:enzymology*; D007425:Intracellular Membranes / Q000201:enzymology*; D009025:Morpholines / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009479:Neuropeptides / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D016716:PC12 Cells / Q000187:drug effects / Q000201:enzymology; D010627:Phenethylamines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D016548:Prosencephalon / Q000201:enzymology; D014176:Protein Biosynthesis / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D020917:Receptor, trkA / Q000187:drug effects* / Q000378:metabolism; D020813:Receptor, trkB / Q000187:drug effects* / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects
D000241:Adenosine; D020126:Brefeldin A; D002867:Chromones; D003513:Cycloheximide; D003609:Dactinomycin; D009025:Morpholines; D009414:Nerve Growth Factors; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D019384:Nucleic Acid Synthesis Inhibitors; D010627:Phenethylamines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D017346:Protein Serine-Threonine Kinases; D011500:Protein Synthesis Inhibitors; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020917:Receptor, trkA; D020813:Receptor, trkB; D043562:Receptors, G-Protein-Coupled; C495403:Adcyap1 protein, rat; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494920:Akt1 protein, rat