PubMed Journals: J Biol Chem
Source: PMID: 9099755
⇦ ⇨ J Biol Chem. 1997 Apr 18;272(16):10957-67.
Autophosphorylation of activation loop tyrosines
regulates signaling by the TRK
nerve growth factor receptor.
Cunningham ME(1), Stephens RM, Kaplan DR,
(1) Department of Pathology and Center of
Neurobiology and Behavior, College of Physicians
and Surgeons, Columbia University, New York,
New York 10032, USA.
Many receptor tyrosine kinases possess an
"activation loop" containing three similarly
placed tyrosine autophosphorylation sites.
To examine their roles in the TRK NGF receptor,
these residues (Tyr-670, Tyr-674, and Tyr-675)
were mutated singly and in all combinations
to phenylalanine and stably expressed in
Trk-deficient PC12nnr5 cells. All mutant
receptors showed significantly diminished
nerve growth factor (NGF)-stimulated
autophosphorylation, indicating impaired
catalytic activity. NGF-induced neurite
outgrowth exhibited dose-responsive behavior
when transfectants were compared by relative
receptor expression and exhibited a functional
hierarchy: wild type > Y670F >/= Y674F >>
Y675F >/= YY670/674FF = YY670/675FF >> YY674/675FF
> YYY670/674/675FFF. NGF-induced tyrosine
phosphorylation of Shc, ERKs, and SNT and
immediate early gene inductions generally
paralleled neurogenic potential. However,
activation of phosphatidylinositol 3'-kinase
and tyrosine phosphorylation of phospholipase
Cgamma-1 was essentially abolished. The
latter effect appears due to selective inability
of the mutated TRKs to autophosphorylate
the tyrosine residue (Tyr-785) required
for binding phospholipase Cgamma-1 and indicates
that the "activation loop" tyrosines participate
in NGF-dependent changes in receptor conformation.
Our findings stress the importance that
expression levels play in assessing the
consequences of receptor mutations and that
all three activation loop tyrosines have
roles regulating both overall and specific
NGF-mediated signaling through TRK.
PMID: 9099755 [Indexed for MEDLINE]