Molecular and Cellular Biology, December 2001, p. 8414-8427, Vol. 21, No. 24
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.24.8414-8427.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Department of Biological Sciences, Auburn University, Auburn, Alabama 36849,1 and Centro de Biologia Molecular `Severo Ochoa' CSIC, Universidad Autonoma, Canto Blanco, 29049 Madrid, Spain2
Received 18 April 2001/Returned for modification 25 May 2001/Accepted 21 September 2001
Atypical protein kinase C (PKC) isoforms are required for nerve
growth factor (NGF)-initiated differentiation of PC12 cells. In the
present study, we report that PKC-
becomes tyrosine phosphorylated in the membrane coincident with activation posttreatment with nerve
growth factor. Tyrosine phosphorylation and activation of PKC-
were
inhibited in a dose-dependent manner by both PP2 and K252a, src and
TrkA kinase inhibitors. Purified src was observed to phosphorylate and
activate PKC-
in vitro. In PC12 cells deficient in src kinase
activity, both NGF-induced tyrosine phosphorylation and activation of
PKC-
were also diminished. Furthermore, we demonstrate activation of
src by NGF along with formation of a signal complex including the TrkA
receptor, src, and PKC-
. Recruitment of PKC-
into the complex was
dependent on the tyrosine phosphorylation state of PKC-
. The
association of src and PKC-
was constitutive but was enhanced by NGF
treatment, with the src homology 3 domain interacting with a PXXP
sequence within the regulatory domain of PKC-
(amino acids 98 to
114). Altogether, these findings support a role for src in regulation
of PKC-
. Tyrosine 256, 271, and 325 were identified as major sites
phosphorylated by src in the catalytic domain. Y256F and Y271F
mutations did not alter src-induced activation of PKC-
, whereas the
Y325F mutation significantly reduced src-induced activation of PKC-
.
The functional relevance of these mutations was tested by determining
the ability of each mutant to support TRAF6 activation of NF-
B, with
significant impairment by the Y325F PKC-
mutant. Moreover, when the
Y352F mutant was expressed in PC12 cells, NGF's ability to promote
survival in serum-free media was reduced. In summary, we have
identified a novel mechanism for NGF-induced activation of atypical PKC
involving tyrosine phosphorylation by c-Src.
Present address: Department of Large Animal Medicine, College of
Veterinary Medicine, University of Georgia, Athens, GA 30602.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|