Kinase activity is not required for alphaCaMKII-dependent presynaptic plasticity at CA3-CA1 synapses - PubMed (original) (raw)

Kinase activity is not required for alphaCaMKII-dependent presynaptic plasticity at CA3-CA1 synapses

Mohammad Reza Hojjati et al. Nat Neurosci. 2007 Sep.

Abstract

Using targeted mouse mutants and pharmacologic inhibition of alphaCaMKII, we demonstrate that the alphaCaMKII protein, but not its activation, autophosphorylation or its ability to phosphorylate synapsin I, is required for normal short-term presynaptic plasticity. Furthermore, alphaCaMKII regulates the number of docked vesicles independent of its ability to be activated. These results indicate that alphaCaMKII has a nonenzymatic role in short-term presynaptic plasticity at hippocampal CA3-CA1 synapses.

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Figures

Figure 1

Figure 1

Phosphorylation of synapsin I and CaMKII-T286/T287 in synaptosomes obtained from αCaMKII mutants. (a) Phosphorylation of synapsin I S603 was not affected by impaired αCaMKII autophosphorylation, but required αCaMKII protein and its activation by Ca2+/calmodulin. (b) Phosphorylation of αCaMKII-T286 and βCaMKII-T287 was absent in αCaMKII-T305D mice. Graph represents data from βCaMKII-T287 only. Error bars indicate s.e.m. Each sample contains pooled fractions from four independent isolations.

Figure 2

Figure 2

Presynaptic short-term plasticity requires αCaMKII protein, but not its autophosphorylation, activation or activity. (a–c) Increased synaptic augmentation in αCaMKII-KO mutant mice was not caused by the lack of CaMKII kinase activity. fEPSP responses (normalized to pretetanus baseline) of CaMKII-KO (a) and CaMKII-T305D (b) mice were recorded at the indicated time after a 10 theta-burst tetanus. Traces are from baseline response (gray) and the response 5 s post-tetanization (black). Augmentation summary of responses obtained 5 s post-tetanus normalized to baseline is shown in c. Black bars represent mutants or drug-treated slices, white bars represent control slices as indicated. (d–f). Decreased synaptic fatigue during repetitive stimulation in αCaMKII-KO mice was not caused by the lack of αCaMKII kinase activity. (d,e) fEPSP responses (normalized against baseline) of CaMKII-KO (d) and CaMKII-T305D (e) mice were recorded during a 10-Hz tetanus. Only the first and even numbered stimuli are shown for clarity. Traces are from wild-type (gray) and αCaMKII-KO slices (black) recorded from stimulus number 21–30. Depletion summary of the last (100) stimulus of the 10-Hz train is shown in f. Black bars represent mutant or drug-treated slices, normalized against the controls as indicated (white bars, set at 100%). Numbers between brackets indicate the number of slices. Error bars indicate s.e.m.

Figure 3

Figure 3

αCaMKII protein regulates the number of docked vesicles. (a) Quantitative electron microscopy of asymmetric synapses on dendritic spines of CA1 pyramidal neurons showed a 20% increase in the number of docked vesicles in αCaMKII-KO mice. (b) Decreasing the depletion rate by lowering extracellular calcium reversed the phenotype of the αCaMKII-KO mice during repetitive stimulation. Error bars indicate s.e.m.

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