, 2008). Additionally, lateral ventricular injection of sAPPα increased the proliferation of NPCs in the subventricular zone, another neurogenic niche

in mouse brain ( Caillé et al., 2004). All ADAM family proteins contain an N-terminal prodomain, which acts to chaperone and ensure the proper Capmatinib mw folding of this family of metalloproteases. Our results show that the cleaved ADAM10 prodomain appears to be quickly degraded in the brain and that cellular trafficking of ADAM10 is not affected by the prodomain mutations. Interestingly, while the prodomain may be degraded, it may still have the ability to affect the mature enzyme via its intramolecular chaperone function. This phenomenon, dubbed “protein memory,” was reported in mutant subtilysin, a serine protease harboring a mutation in its prodomain (Shinde et al., 1997). The point mutation yielded mature subtilysin that had a different structure and activity via “structural imprinting” during protein folding (Shinde et al., selleck chemicals llc 1997). Improperly chaperoned, mis-folded proteases can be restructured and become active

by ectopic expression of WT prodomain (Cao et al., 2000). In our mammalian cell-based studies, WT but not mutant ADAM10 prodomain rescued the α-secretase activity of inactive ADAM10 expressed from a prodomain-deleted cDNA construct. This indicates impairment of the chaperone function of the prodomain by the LOAD mutations (Figure 8C). In further support of this conclusion, secondary structure predictions showed that the only α-helix in the prodomain can be terminated by the R181G mutation (McGuffin

et al., 2000). To date, a few pathogenic amino acid substitutions, which are why not present in the mature forms, have been associated with diseases. But to our knowledge, the two LOAD ADAM10 mutations are the first to be associated with the etiology of any disease by impairing the intramolecular chaperone function of a prodomain. Increased ADAM10 α-secretase activity could potentially be achieved by multiple different mechanisms, including the activation of ADAM10 gene transcription by retinoic acid, the inhibition of natural ADAM10 inhibitors (e.g., TIMPs, tissue inhibitor of metalloproteases), and the modulation of ADAM10 cellular trafficking (Lichtenthaler, 2011). While dozens of proteins have been reported as ADAM10 substrates (Pruessmeyer and Ludwig, 2009), only a handful are related to brain and neuronal function. Moreover, in contrast to the ADAM10 knockdown, our data and a previous report by Postina et al. (2004) support that modest elevation of ADAM10 is relatively well tolerated and does not affect Notch1 signaling in adult brain.

, 1997). Similar to humans with AS, mice lacking maternal Ube3a (Ube3am−/p+) have

abnormal EEG activity and are susceptible to cortical seizures, suggesting that loss of Ube3a might disrupt the excitatory/inhibitory balance in the neocortex ( Jiang et al., 1998). Loss of maternally inherited Ube3a results in decreased excitatory synaptic drive onto pyramidal neurons in layer 2/3 (L2/3) of neocortex, as evidenced by a loss of dendritic spines ( Yashiro et al., 2009). Decreased Ube3a-mediated PI3K inhibitor proteasomal degradation of Arc and Ephexin5 proteins may lead to excitatory synaptic defects ( Greer et al., 2010 and Margolis et al., 2010). These observations suggest a mechanism for how the loss of Ube3a may cause fewer and/or weaker excitatory synapses. While these deficits may be relevant to cognitive phenotypes in Ube3am−/p+ mice, they would not on their own predict hyperexcitability and increased seizure susceptibility. We hypothesized that Ube3a loss results in more severe inhibitory deficits, with the net outcome favoring cortical

hyperexcitability. Here, we use the visual cortex as a model to study the role of Ube3a in the establishment and function of inhibitory circuits. We show that Ube3am−/p+ mice have an abnormal accumulation of clathrin-coated vesicles at inhibitory axon terminals, indicating a defect in vesicle cycling. Consistent with this observation, inhibitory synaptic transmission MAPK inhibitor onto L2/3 pyramidal neurons recovers slower following vesicle depletion in Ube3am−/p+ mice, compared to wild-types. Recovery following high-frequency stimulation of excitatory synapses onto L2/3 pyramidal neurons, however, is

normal. This discrepancy among synapse types may further contribute to excitatory/inhibitory also imbalance during high levels of activity. Finally, we show that synaptic inputs onto inhibitory neurons in Ube3am−/p+ mice are largely normal. We conclude that neuron type-specific synaptic deficits are likely to underlie neocortical excitatory/inhibitory imbalance in AS. An excitatory/inhibitory imbalance in AS could arise from reduced numbers of inhibitory interneurons, abnormal inhibitory connectivity, and/or decreased inhibitory neurotransmission. To test the first possibility, we performed immunohistochemistry for three markers—parvalbumin, calretinin, and somatostatin—which together label 96% of the total GABAergic interneurons in L2/3 of mouse primary visual cortex (V1) (Gonchar et al., 2007). We compared Ube3am−/p+ mice and their wild-type (WT) 129Sv/Ev strain littermate controls at postnatal day 80 (P80), an age where AS model mice exhibit abnormal EEG patterns and are susceptible to seizures ( Jiang et al., 1998). We found no differences in the density of inhibitory interneurons expressing these markers ( Figures 1A and 1B), implying that the relative number of inhibitory interneurons is normal in L2/3 of V1.