A novel mutation within the extracellular domain of TrkA causes constitutive receptor activation.
The TrkA NGF receptor extracellular region contains three leucine repeats flanked by cysteine clusters and two immunoglobulin-like domains that are required for specific ligand binding. Deletion of the immunoglobulin-like domains abolishes NGF binding and causes ligand independent activation of the receptor. Here we report a specific mutation that increases the binding affinity of the TrkA receptor for NGF. A change of proline 203 to alanine (P203A) in the linker region between the leucine repeats and the first Ig-like domain increased NGF binding by decreasing the ligand rate of dissociation. This mutated receptor was appropriately expressed on the cell surface and promoted ligand-independent neurite outgrowth in PC12nnr5 cells. The mutant receptor was capable of spontaneous dimerization and was constitutively phosphorylated in the absence of ligand. Moreover, expression of TrkA-P203A receptor in fibroblasts induced DNA synthesis and transformation and generated tumours in nude mice. These data suggest that domains outside of the immunoglobulin-like structure contribute to ligand binding and constitutive activation of Trk receptors.
Arevalo
J C
JC
Instituto de Microbiologia Bioquimica, Departamento de Microbiologia y Genetica, CSIC Universidad de Salamanca, 37007 Salamanca, Spain.
Conde
B
B
Hempstead
B I
BI
Chao
M V
MV
Martín-Zanca
D
D
Pérez
P
P
D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D003114:Colony-Forming Units Assay; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D020932:Nerve Growth Factor / Q000378:metabolism*; D016501:Neurites / Q000502:physiology; D016716:PC12 Cells / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D020917:Receptor, trkA / Q000235:genetics* / Q000378:metabolism*; D013329:Structure-Activity Relationship
D008024:Ligands; D020932:Nerve Growth Factor; D020917:Receptor, trkA