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The protein kinase C (PKC) substrate GAP‐43 is already expressed in neural precursor cells, colocalizes with PKCη and binds calmodulin
Author(s) -
Esdar Christina,
Oehrlein Silke A.,
Reinhardt Sigrid,
Maelicke Alfred,
Herget Thomas
Publication year - 1999
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1999.00455.x
Subject(s) - protein kinase c , microbiology and biotechnology , calmodulin , kinase , substrate (aquarium) , chemistry , biology , biochemistry , enzyme , ecology
Expression of the growth‐associated protein of 43‐kDa (GAP‐43), which is described as a postmitotic, neuron‐specific major protein kinase C (PKC) substrate, was investigated in the murine embryonic carcinoma cell line PCC7‐Mz1 which develops into a brain‐tissue‐like pattern of neuronal, fibroblast‐like and astroglial cells upon stimulation with all‐ trans retinoic acid (RA). GAP‐43 expression was very low in stem cells, but increased on mRNA and protein level within the 12 h after differentiation was initiated. While the P1 promoter of the GAP‐43 gene gave rise to a 1.6‐kb mRNA and was already active at a very low level in PCC7‐Mz1 stem cells, transcription of the P2 promoter, which resulted in a 1.4‐kb mRNA, was completely blocked in stem cells but increased rapidly after RA treatment. Within the first 2 days of neural differentiation, GAP‐43 was localized with the cytoplasmic membrane and the Golgi complex of proliferating neural precursor cells. Then, GAP‐43 was translocated to the growth cones and neurites, and from day 6, when neurons began to acquire polarity, the protein was found in the axons. GAP‐43 was never detected in the non‐neuronal PCC7‐Mz1 derivatives, i.e. in fibroblasts or glial cells. In the foetal rat brain (prenatal day F11), GAP‐43 was expressed in the optic stalk, the lense plakode and in the postmitotic neurons of the marginal zone of the hindbrain. Moreover, in a layer between the ventricular and marginal zone of the hindbrain (F13) and forebrain (F15), GAP‐43 was already expressed in mitotic neural precursor cells. In PCC7‐Mz1 cultures, 2 days after addition of RA, GAP‐43 became phosphorylated upon activation of PKC, and colocalized specifically with the novel PKC isoform η. Phosphorylation of GAP‐43 caused a disruption of its complex with calmodulin. These data demonstrate that GAP‐43 is already a functional PKC substrate in prolific neuronal precursor cells, and may participate in neuronal cell lineage determination.