The long and short isoforms of Ret function as independent signaling complexes.
Ret, the receptor tyrosine kinase for the glial cell line-derived neurotrophic factor family ligands (GFLs), is alternatively spliced to yield at least two isoforms, Ret9 and Ret51, which differ only in their C termini. To identify tyrosines in Ret that are autophosphorylation sites in neurons, we generated antibodies specific to phosphorylated Y905Ret, Y1015Ret, Y1062Ret, and Y1096Ret, all of which are autophosphorylated in cell lines. All four of these tyrosines in Ret became phosphorylated rapidly upon activation by GFLs in sympathetic neurons. These tyrosines remained phosphorylated in sympathetic neurons in the continued presence of GFLs, albeit at a lower level than immediately after GFL treatment. Comparison of GFL activation of Ret9 and Ret51 revealed that phosphorylation of Tyr(905) and Tyr(1062) was greater and more sustained in Ret9 as compared with Ret51. In contrast, Tyr(1015) was more highly phosphorylated over time in Ret51 than in Ret9. Surprisingly, Ret9 and Ret51 did not associate with each other in sympathetic neurons after glial cell line-derived neurotrophic factor stimulation, even though they share identical extracellular domains. Furthermore, the signaling complex associated with Ret9 was markedly different from the Ret51-associated signaling complex. Taken together, these data provide a biochemical basis for the dramatic functional differences between Ret9 and Ret 51 in vivo.
Tsui-Pierchala
Brian A
BA
Departments of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
Ahrens
Rebecca C
RC
Crowder
Robert J
RJ
Milbrandt
Jeffrey
J
Johnson
Eugene M
EM
D000818:Animals; D029721:Drosophila Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D009414:Nerve Growth Factors / Q000494:pharmacology; D051101:Neurturin; D010766:Phosphorylation; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000502:physiology*; D051096:Proto-Oncogene Proteins c-ret; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000502:physiology*; D017783:Superior Cervical Ganglion / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
D029721:Drosophila Proteins; C495041:Gdnf protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D009414:Nerve Growth Factors; D051101:Neurturin; C495057:Nrtn protein, rat; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D014443:Tyrosine; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; C495001:Ret protein, rat