Mapping of atypical protein kinase C within the nerve growth factor signaling cascade: relationship to differentiation and survival of PC12 cells.
The pathway by which atypical protein kinase C (aPKC) contributes to nerve growth factor (NGF) signaling is poorly understood. We previously reported that in PC12 cells NGF-induced activation of mitogen-activated protein kinase (MAPK) occurs independently of classical and nonclassical PKC isoforms, whereas aPKC isoforms were shown to be required for NGF-induced differentiation. NGF-induced activation of PKC-iota was observed to be dependent on phosphatidylinositol 3-kinase (PI3K) and led to coassociation of PKC-iota with Ras and Src. Expression of dominant negative mutants of either Src (DN2) or Ras (Asn-17) impaired activation of PKC-iota by NGF. At the level of Raf-1, neither PKC-iota nor PI3 kinase was required for activation; however, PKC-iota could weakly activate MEK. Inhibitors of PKC-iota activity and PI3K had no effect on NGF-induced MAPK or p38 activation but reduced NGF-stimulated c-Jun N-terminal kinase activity. Src, PI3K, and PKC-iota were likewise required for NGF-induced NF-kappaB activation and cell survival, whereas Ras was not required for either survival or NF-kappaB activation but was required for differentiation. IKK existed as a complex with PKC-iota, Src and IkappaB. Consistent with a role for Src in regulating NF-kappaB activation, an absence of Src activity impaired recruitment of PKC-iota into an IKK complex and markedly impaired NGF-induced translocation of p65/NF-kappaB to the nucleus. These findings reveal that in PC12 cells, aPKCs comprise a molecular switch to regulate differentiation and survival responses coupled downstream to NF-kappaB. On the basis of these findings, Src emerges as a critical upstream regulator of both PKC-iota and the NF-kappaB pathway.
Wooten
M W
MW
Department of Biological Sciences, Program in Cell and Molecular Biosciences, Auburn University, AL 36849, USA. mwwooten@ag.auburn.edu
Seibenhener
M L
ML
Neidigh
K B
KB
Vandenplas
M L
ML
D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation; D051550:I-kappa B Kinase; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D016716:PC12 Cells / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases; D018631:ras Proteins / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism; D000099293:Protein Kinase C-lambda
D051550:I-kappa B Kinase; D007527:Isoenzymes; D048031:JNK Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D048051:p38 Mitogen-Activated Protein Kinases; D018631:ras Proteins; D019061:src-Family Kinases; D000099293:Protein Kinase C-lambda; C115015:PKC-3 protein