Cm. Atkins et al., INCREASED PHOSPHORYLATION OF MYELIN BASIC-PROTEIN DURING HIPPOCAMPAL LONG-TERM POTENTIATION, Journal of neurochemistry, 68(5), 1997, pp. 1960-1967
Hippocampal long-term potentiation (LTP) is a long-lasting and rapidly
induced increase in synaptic strength. Previous experiments have dete
rmined that persistent activation of protein kinase C (PKC) contribute
s to the early maintenance phase of LTP (E-LTP). Using the back-phosph
orylation method, we observed an increase in the phosphorylation of a
21-kDa PKC substrate, termed p21, 45 min after LTP was induced in the
CAI region of the hippocampus. p21 was found to have the same apparent
molecular weight as the 18.5-kDa isoform of myelin basic protein (MBP
) and was recognized by an antibody to MBP in western blotting and imm
unoprecipitation. Furthermore, p21 from control and potentiated hippoc
ampal slices and purified MBP have identical phosphopeptide maps when
back-phosphorylated and then digested with either endoproteinase Lys-C
or endoproteinase Asp-N, suggesting that p21 and MBP are identical pr
oteins. As there was no observed change in the amount of MBP in LTP, t
he increase in MBP phosphorylation during LTP cannot be explained by a
change in the amount of protein. From these experiments, we conclude
that the phosphorylation of the 18.5-kDa isoform of MBP is increased d
uring E-LTP.