Notch signalling becomes transiently attenuated during long-term memory consolidation in adult Wistar rats.
Recent evidence has suggested a role for Notch in memory consolidation but the means by which this evolutionarily conserved mechanism serves these plasticity-related processes remains to be established. We have examined a role for this signalling pathway in the hippocampal dentate gyrus of Wistar rats at increasing times following passive avoidance conditioning. Our principal finding is that a transient attenuation of Notch signalling occurs at the 10-12h post-training time. In this period, extracellular Notch-1 protein fragment exhibited a significant 2- to 3-fold increase but, by contrast, Notch-1 mRNA levels were significantly reduced. Moreover, transient inactivation of Notch-1 signalling was further suggested by concomitant reductions in the Notch ligand Jagged-1 and Notch-1 target protein Hes-1 mRNA levels. The C-terminal fragment of PS-1, necessary for gamma-secretase activity, was also significantly reduced at the 12h post-training time. These events were commensurate with the increase of a Notch immunoreactive fragment of 66 kDa in the nuclear fraction of the dentate gyrus. This fragment, identified with two different Notch-1 antisera, was not the expected NICD polypeptide of approximately 110 kDa and its accumulation was found to correlate with a significantly reduced expression of the Hes-1 transcriptional repressor. During the period of reduced Notch activity, a transient increase in soluble beta-catenin and GSK-3beta phosphorylation was observed, indicating a reciprocal activation of the Wnt signalling pathway. As down-regulation of Notch signalling promotes differentiation and neurite outgrowth in post-mitotic neurons, it is proposed that this pathway regulates the integration of synapses transiently produced during memory consolidation.
Conboy
Lisa
L
School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
Seymour
Claire M
CM
Monopoli
Marco P
MP
O'Sullivan
Niamh C
NC
Murphy
Keith J
KJ
Regan
Ciaran M
CM
D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D018891:Dentate Gyrus / Q000378:metabolism*; D045604:Extracellular Fluid / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D053764:Presenilin-1 / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D018709:Statistics, Nonparametric; D013997:Time Factors
C497763:Notch1 protein, rat; D053764:Presenilin-1; D012333:RNA, Messenger; D051881:Receptor, Notch1; D053829:Amyloid Precursor Protein Secretases