β-Amyloid-induced Dynamin 1 Depletion in Hippocampal Neurons

Abstract

Synaptic dysfunction is one of the earliest events in the pathogenesis of Alzheimer disease (AD). However, the molecular mechanisms underlying synaptic defects in AD are largely unknown. We report here that β-amyloid (Aβ), the main component of senile plaques, induced a significant decrease in dynamin 1, a protein that is essential for synaptic vesicle recycling and, hence, for memory formation and information processing. The Aβ-induced dynamin 1 decrease occurred in the absence of overt synaptic loss and was also observed in the Tg2576 mouse model of AD. In addition, our results provided evidence that the Aβ-induced decrease in dynamin 1 was likely the result of a calpain-mediated cleavage of dynamin 1 protein and possibly the down-regulation of dynamin 1 gene expression. These data suggest a mechanism to explain the early cognitive loss without a major decline in synapse number observed in AD and propose a novel therapeutic target for AD intervention. Synaptic dysfunction is one of the earliest events in the pathogenesis of Alzheimer disease (AD). However, the molecular mechanisms underlying synaptic defects in AD are largely unknown. We report here that β-amyloid (Aβ), the main component of senile plaques, induced a significant decrease in dynamin 1, a protein that is essential for synaptic vesicle recycling and, hence, for memory formation and information processing. The Aβ-induced dynamin 1 decrease occurred in the absence of overt synaptic loss and was also observed in the Tg2576 mouse model of AD. In addition, our results provided evidence that the Aβ-induced decrease in dynamin 1 was likely the result of a calpain-mediated cleavage of dynamin 1 protein and possibly the down-regulation of dynamin 1 gene expression. These data suggest a mechanism to explain the early cognitive loss without a major decline in synapse number observed in AD and propose a novel therapeutic target for AD intervention. Senile plaques, neurofibrillary tangles, synapse loss, and gross neurodegeneration are common findings in the brain of AD 1The abbreviations used are: AD, Alzheimer disease; Aβ, β-amyloid; MEM, minimum essential medium; MDL-28170, benzyloxycarbonyl-Val-Phe-CHO; PBS, phosphate-buffered saline; RT, reverse transcription; WT, wild-type. patients (1Glenner G.G. Wong C.W. Biochem. Biophys. Res. Commun. 1984; 122: 1131-1135Crossref PubMed Scopus (1261) Google Scholar, 2Grundke-Iqbal I. Iqbal K. Quinlan M. Tung Y.C. Zaidi M.S. Wisniewski H.M. J. Biol. Chem. 1986; 261: 6084-6089Abstract Full Text PDF PubMed Google Scholar, 3Terry R.D. Masliah E. Salmon D.P. Butters N. DeTeresa R. Hill R. Hansen L.A. Katzman R. Ann. Neurol. 1991; 30: 572-580Crossref PubMed Scopus (3423) Google Scholar, 4DeKosky S.T. Scheff S.W. Ann. Neurol. 1990; 27: 457-464Crossref PubMed Scopus (1701) Google Scholar). Numerous genetic, biochemical, and animal model studies have implicated the gradual buildup of Aβ, the main component of senile plaques, as the catalyst for AD. However, the mechanistic link between Aβ accumulation and the progressive cognitive impairment associated with this disease has not been elucidated. Synapse loss seems to be the best morphological correlate of the functional deficits observed in the mid-to-late stages of AD (3Terry R.D. Masliah E. Salmon D.P. Butters N. DeTeresa R. Hill R. Hansen L.A. Katzman R. Ann. Neurol. 1991; 30: 572-580Crossref PubMed Scopus (3423) Google Scholar, 4DeKosky S.T. Scheff S.W. Ann. Neurol. 1990; 27: 457-464Crossref PubMed Scopus (1701) Google Scholar). In contrast, patients in the earliest stages of the disease show no significant decline in synapse number (5Tiraboschi P. Hansen L.A. Alford M. Masliah E. Thal L.J. Corey-Bloom J. Neurology. 2000; 55: 1278-1283Crossref PubMed Scopus (118) Google Scholar). Based on these findings, it has been hypothesized that a stage of synaptic dysfunction might precede frank synapse loss, plaque accumulation, and tangle formation in AD (6Selkoe D.J. Science. 2002; 298: 789-791Crossref PubMed Scopus (3438) Google Scholar, 7Yao P.J. Trends Neurosci. 2004; 27: 24-29Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar). The mechanisms underlying such synaptic dysfunction remain unknown. It is tempting to speculate that proteins involved in synaptic vesicle biogenesis and/or recycling might play a critical role in AD. Data obtained recently seem to support this view. Thus, changes in the levels of a number of presynaptic proteins, including SNAP-25, syntaxin, and synaptotagmin, have been reported in AD (8Honer W.G. Neurobiol. Aging. 2003; 24: 1047-1062Crossref PubMed Scopus (116) Google Scholar). More recently, dynamin 1, a protein highly enriched in presynaptic terminals, has been shown to be significantly reduced in AD brains (9Yao P.J. Zhu M. Pyun E.I. Brooks A.I. Therianos S. Meyers V.E. Coleman P.D. Neurobiol. Dis. 2003; 12: 97-109Crossref PubMed Scopus (193) Google Scholar). Dynamin 1, a well studied neuron-specific mechanochemical GTPase, pinches off synaptic vesicles, freeing them from the membrane and allowing them to re-enter the synaptic vesicle pool to be refilled for future release (10Clark S.G. Shurland D.L. Meyerowitz E.M. Bargmann C.I. van der Bliek A.M. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 10438-10443Crossref PubMed Scopus (100) Google Scholar, 11Damke H. Baba T. Warnock D.E. Schmid S.L. J. Cell Biol. 1994; 127: 915-934Crossref PubMed Scopus (1046) Google Scholar). The essential role for dynamin 1 in vesicle scission and synaptic function has been best supported by studies of the Drosophila model shibire, a temperature-sensitive mutant of a dynamin ortholog (12Koenig J.H. Ikeda K. J. Neurosci. 1989; 9: 3844-3860Crossref PubMed Google Scholar, 13van der Bliek A.M. Meyerowitz E.M. Nature. 1991; 351: 411-414Crossref PubMed Scopus (596) Google Scholar). At restrictive temperatures these flies displayed a paralysis phenotype. This functional deficit was accompanied by the depletion of synaptic vesicles and the accumulation of invaginated pits at pre-synaptic membranes adjacent to the synaptic clefts. Collectively, these data suggested that the stressors that induce dynamin 1 loss-of-function could result in the diminution of available synaptic vesicles leading to synaptic dysfunction. In the present study we analyzed whether Aβ was one of such stressors using hippocampal neurons that develop in culture and in an AD animal model system. Our results showed that Aβ induced a significant reduction in dynamin 1 levels that preceded synapse loss in both model systems. In cultured neurons, our data suggested that the Aβ-induced decrease in dynamin 1 was likely the result of a bimodal mechanism that involved calpain-mediated proteolysis and the down-regulation of dynamin 1 gene expression. On the other hand, in the AD mouse model Tg2576 the decrease in dynamin 1 was mainly the result of calpain activation. These mechanisms identify novel therapeutic targets to address the synaptic dysfunction preceding synapse loss and neurodegeneration in the context of AD. Preparation of Hippocampal Cultures—Embryonic day 18 rat embryos were used to prepare primary hippocampal cultures as described previously (14Ferreira A. Li L. Chin L.S. Greengard P. Kosik K.S. Mol. Cell. Neurosci. 1996; 8: 286-299Crossref PubMed Scopus (22) Google Scholar, 15Dawson H.N. Ferreira A. Eyster M.V. Ghoshal N. Binder L.I. Vitek M.P. J. Cell Sci. 2001; 114: 1179-1187PubMed Google Scholar). Briefly, hippocampi were dissected and freed of meninges. The cells were dissociated by trypsinization followed by trituration with a fire-polished Pasteur pipette. For biochemical experiments, hippocampal neurons were plated at high density (500,000 cells per 60-mm dish) in MEM with 10% horse serum (MEM10). After 2 h, the medium was changed to glia-conditioned MEM containing N2 supplements plus ovalbumin (0.1%) and sodium pyruvate (0.1 mm) (16Bottenstein J.E. Sato G.H. Proc. Natl. Acad. Sci. U. S. A. 1979; 76: 514-517Crossref PubMed Scopus (2015) Google Scholar). For immunocytochemistry studies the neurons were plated onto poly-l-lysine-coated coverslips in MEM10. After 2 h, the coverslips were transferred to dishes containing an astroglial monolayer and maintained in MEM containing N2 supplements plus ovalbumin (0.1%) and sodium pyruvate (0.1 mm). These cultures contain ∼95% pyramidal neurons and 5% glial cells. Aβ Treatment—Synthetic Aβ-(1-40) or Aβ-(1-42) (Sigma-Aldrich) was dissolved in N2 medium at 0.1 mg/ml and incubated for 4 days at 37 °C to preaggregate the peptide (17Ferreira A. Lu Q. Orecchio L. Kosik K.S. Mol. Cell. Neurosci. 1997; 9: 220-234Crossref PubMed Scopus (171) Google Scholar). This preaggregated Aβ was added to the culture medium at final concentrations ranging from 0.02 to 20 μm. For some experiments, the aggregated Aβ was centrifuged at 100,000 × g for 1 h to separate the oligomeric (supernatant) from the fibrillar (pellet) forms of the peptide. The oligomeric fraction was obtained by removing the supernatant. The fibrillar fraction was obtained by resuspending the pellet in a volume of N2 medium equal to the supernatant. These fractions were added directly to the neurons at final Aβ concentrations calculated using the initial concentration of the monomeric form of the peptide. Monomeric Aβ were by the peptide in N2 medium Hippocampal neurons were in the of the peptide for to and in of including the and the calpain and were added to the medium of hippocampal neurons been in culture 1 h to and for the of the Aβ For using (Sigma-Aldrich) and calpain from cultured hippocampal neurons or from the hippocampal were incubated with or calpain for 1 h at 37 were used at final concentrations ranging from to and were from hippocampal neurons that in culture or in prepare these hippocampal neurons in culture for were in PBS, and in a for were also dissected from and The used for these were Tg2576 Tg2576 and Tg2576 were in and for were on and transferred to membranes was using the 1 an to 1 from 2 A. A. J. Neurosci. Res. PubMed Scopus Google and to followed by were used for the of were and using a of the was using were using as an neurons cultured for were for 20 with in containing were in in for and in The cells were in 10% serum in for 1 h at 37 °C and to the primary at 4 The neurons were in and incubated with for 1 h at 37 The primary used for were 1 and The used were the and and cultured hippocampal neurons were using dynamin 1 and as described were for the of dynamin 1 and was at a using For the of the Aβ the and oligomeric fractions were on a with and in The fractions were in 10% serum in for 1 h at 37 °C and to at 4 The fractions were in and incubated with for 1 h at 37 cultured hippocampal neurons and hippocampi obtained from and Tg2576 were in was by to the was in containing 1 of of reverse 1 of 1 1 1 1 and 2 of number were incubated at °C for at °C for and at °C for was using 18 as and dynamin as the target were in using of and with as the were in and analyzed as of dynamin 1 in cultured hippocampal neurons cultured hippocampal neurons and Tg2576 hippocampi hippocampi using the Aβ a Dynamin 1 in Hippocampal whether the of Aβ could a depletion of dynamin 1, we analyzed dynamin 1 protein levels in cultured hippocampal neurons with We have this model the is one of the brain in AD. In addition, synaptic in the is to memory we and have shown previously in culture for hippocampal neurons the molecular and functional of neurons in (17Ferreira A. Lu Q. Orecchio L. Kosik K.S. Mol. Cell. Neurosci. 1997; 9: 220-234Crossref PubMed Scopus (171) Google Scholar, J. Neurosci. 1984; PubMed Google Scholar, J. Neurosci. 1984; PubMed Google Scholar). The of Aβ-(1-40) to the culture medium of these hippocampal neurons induced a significant decrease in dynamin 1 as by Dynamin a dynamin as well as a pre-synaptic were also in neurons However, the loss of dynamin 1 and 2 was that of is a synaptic vesicle protein with that it to synaptic vesicles in the presynaptic of Cell. Full Text PDF PubMed Scopus Google Scholar). levels correlate with synapse and are used to for loss of (5Tiraboschi P. Hansen L.A. Alford M. Masliah E. Thal L.J. Corey-Bloom J. Neurology. 2000; 55: 1278-1283Crossref PubMed Scopus (118) Google Scholar, Corey-Bloom J. P. R. Masliah E. Thal L.J. Neurol. PubMed Scopus Google Scholar). On the other hand, no changes in the levels of dynamin a dynamin also in the were in neurons with in to the changes in dynamin 1 levels described a dynamin 1 was in the neurons results were obtained cultured hippocampal neurons were incubated with preaggregated Aβ-(1-42) described were with whether Aβ induced the decrease of dynamin levels in a hippocampal neurons were incubated with Aβ at final concentrations ranging from 0.02 to 20 for The of dynamin 1, and as well as in was by of 1, and Our results showed a decrease in the levels of dynamin 1 and not of dynamin in neurons as with However, levels were cultured hippocampal neurons were incubated with Aβ at concentrations 20 μm. These results suggested that synapse were not at these On the other hand, the of the dynamin 1 was in from hippocampal neurons cultured in the of Aβ at of the concentrations analyzed we whether Aβ dynamin levels in a For these experiments, hippocampal neurons in culture for were incubated with Aβ for to h 1, and The of Aβ on dynamin 1 and 2 levels was as early as h the of the peptide. In contrast, no changes in dynamin and levels were the analyzed 1, and the of Aβ has been to play a critical role in we form of the Aβ peptide was these on dynamin The preaggregated Aβ likely both fibrillar forms and oligomeric forms of the peptide. we these forms of Aβ by whether we the fibrillar Aβ from the oligomeric Aβ, we fraction with an Aβ The showed with the oligomeric fraction showed the fibrillar fraction showed mainly whether these separate forms of Aβ on dynamin 1, we incubated cultured hippocampal neurons with the and fibrillar forms of Aβ for showed a decrease in dynamin 1 levels in obtained from hippocampal neurons incubated with the and oligomeric forms of Aβ and We also observed the of the in the and oligomeric with Aβ also the of dynamin 1 in hippocampal In neurons, dynamin 1 was highly enriched in the In addition, dynamin 1 was the by these pyramidal neurons in a the dynamin 1 with at synaptic and However, dynamin 1 was also in The of hippocampal neurons with Aβ for h the the of In contrast, dynamin 1 was the and was mainly to the and adjacent of the by hippocampal neurons a not with that of dynamin 1 in and of the dynamin 1 and showed a number of by in dynamin 1 and On the other hand, a significant decrease in the number of dynamin 1 not was in These data suggested that Aβ levels of dynamin 1 in the present the of the by hippocampal Aβ Dynamin 1 by a to and/or down-regulation of the of dynamin 1 to the Aβ-induced decrease in protein levels observed in cultured hippocampal The results described previously the of a molecular in neurons suggested that a was involved in the decrease of dynamin 1 to play a role in the pathogenesis of AD are and calpain K. J.E. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, T. S. J. K. Neurosci. PubMed Scopus Google Scholar, Zhu J. A. M. M.S. H. S. S. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, V.E. Ann. Neurol. 2003; PubMed Scopus Google Scholar, T. T. P. A. A. N. Li J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). we the of these to dynamin 1 in from cultured hippocampal neurons were incubated with of or to dynamin 1 at of the concentrations used in our in On the other hand, showed a decrease of dynamin 1 incubated with In addition, calpain cleavage a dynamin 1 to the one hippocampal neurons were incubated with Aβ whether Aβ could induce the proteolysis of dynamin 1 in hippocampal neurons, we the neurons with of or calpain to Aβ The not the dynamin 1 decrease induced by calpain and the cleavage of dynamin 1 in a we the of Aβ on dynamin 1 in cultured hippocampal were incubated with Aβ for and h, and was for showed a decrease in dynamin 1 from cultured hippocampal neurons that were incubated with Aβ for and h showed a significant decrease of dynamin 1 from hippocampal neurons incubated in the of Aβ for and h as with and these data suggested that Aβ induced the decrease of dynamin 1 in cultured hippocampal neurons by a bimodal both calpain-mediated proteolysis and a decrease in dynamin 1 expression. Dynamin 1 in the of Tg2576 we studied whether Aβ on dynamin 1 in the AD animal model Tg2576 a in the protein that of the Aβ peptide K. P. S. S. Science. 1996; PubMed Scopus Google Scholar). These of AD including Aβ plaque at of K. P. S. S. Science. 1996; PubMed Scopus Google Scholar). On the other hand, cognitive deficits were as early as 4 in Tg2576 M. H. S.G. M. R. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). changes in the number of were not in Tg2576 D.L. Res. 2002; PubMed Scopus Google Scholar, J. Neurosci. 2002; PubMed Google Scholar). The cognitive observed in these in the absence of suggested a mechanism Dynamin 1 might play a role in such a this we dynamin 1 and protein levels in from the hippocampi of and Tg2576 with of and Dynamin 1 and levels were using neuron-specific as an in dynamin 1 protein levels were in the Tg2576 as with 2 and On the other hand, at of Tg2576 showed a significant decline in dynamin 1 This in dynamin 1 levels at of Tg2576 show an decrease in dynamin 1 levels with no changes in protein levels were in the Tg2576 with the analyzed and These data that a decrease in dynamin 1 protein occurred from synapse loss both in neurons that in culture and in of Dynamin 1 in Tg2576 to calpain in the cleavage of dynamin 1 and the of a of in cultured hippocampal calpain was in the of Tg2576 we to a dynamin 1 at the molecular dynamin 1 were in the or Tg2576 contrast, were directly dynamin 1 in and Tg2576 whether calpain was for this dynamin 1 we incubated hippocampal obtained from Tg2576 with calpain for 1 showed the of a dynamin 1 in incubated with calpain and from Tg2576 On the other hand, no such was in obtained from calpain in the of these we analyzed the of a common calpain R. M. Proc. Natl. Acad. Sci. U. S. A. 1984; PubMed Scopus Google Scholar). of calpain results in the cleavage of to of and molecular S. J. Google Scholar). in the of was in Tg2576 with and at and calpain in these seems to correlate with the decrease in dynamin 1 and the of the dynamin 1 We studied dynamin 1 levels in the hippocampi of these showed that at 2 and Tg2576 have no significant in dynamin 1 levels with and significant in dynamin 1 was in Tg2576 with The results that Aβ induced a decrease of dynamin 1 in hippocampal In addition, our findings suggested that this Aβ-induced dynamin 1 decrease was the result of a bimodal mechanism that involved calpain-mediated proteolysis and down-regulation of dynamin 1 gene in cultured hippocampal In Tg2576 on the other hand, the decrease in the dynamin 1 protein was likely to calpain-mediated the of dynamin 1 to synaptic these results the molecular mechanisms underlying the cognitive decline observed in the early stages of AD. to an between our of the mechanisms leading to Aβ accumulation in brain and synaptic deficits in AD Synaptic dysfunction has been a tempting for the cognitive deficits observed at early stages of the disease no significant decline in the synapse number could be (5Tiraboschi P. Hansen L.A. Alford M. Masliah E. Thal L.J. Corey-Bloom J. Neurology. 2000; 55: 1278-1283Crossref PubMed Scopus (118) Google Scholar). However, the mechanisms underlying these functional deficits are not These results that changes in dynamin 1 could at in these Thus, concentrations of Aβ Aβ levels in AD L. L. T. J.H. J. J. Full Text Full Text PDF PubMed Scopus Google significantly reduced dynamin 1 protein levels in a and in cultured hippocampal used at these concentrations Aβ induced the reduction in dynamin 1 to synapse loss and/or in cultured hippocampal results were obtained the levels of dynamin 1 were analyzed in the hippocampal of Tg2576 the used AD animal These have of Aβ-(1-40) and Aβ-(1-42) in showed a significant reduction in dynamin 1 protein levels in the absence of synapse loss as using as a synaptic Our results suggested that dynamin 1 levels might to changes in synaptic vesicle recycling and the accumulation of vesicles at the synaptic function in the of the This on synaptic vesicle in of for memory Cell. 1994; Full Text PDF PubMed Scopus Google Scholar, 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). Our data support studies that Aβ-induced cognitive decline is a or in animal D.J. Neurosci. 8: PubMed Scopus Google Scholar, K.S. S. Neurosci. 2002; PubMed Scopus Google Scholar). These studies have suggested that decline to Aβ is not of frank synapse loss or neurodegeneration a stage of synaptic dysfunction that not in to and It is tempting to speculate that this stage of synaptic dysfunction is by a decrease in dynamin 1, leading to the depletion of synaptic vesicles to the to from the presynaptic it has been that the synaptic in the and was significantly in AD brains in P. M. J. Res. PubMed Scopus Google Scholar, S.W. S.T. Neurobiol. Aging. 1990; PubMed Scopus Google Scholar). This could be a result of the accumulation of synaptic vesicles at the have been described in temperature-sensitive of a dynamin ortholog in Drosophila (12Koenig J.H. Ikeda K. J. Neurosci. 1989; 9: 3844-3860Crossref PubMed Google Scholar, 13van der Bliek A.M. Meyerowitz E.M. Nature. 1991; 351: 411-414Crossref PubMed Scopus (596) Google Scholar). This study also provided the mechanisms leading to Aβ-induced decrease in dynamin 1 Our in and in suggested that calpain dynamin 1 proteolysis in hippocampal The of this in the of Aβ is in with that AD patients levels of calpain in K. J.E. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, T. S. J. K. Neurosci. PubMed Scopus Google Scholar, T. T. P. A. A. N. Li J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). has also been to the of leading to of of AD M.S. Li M. J. Nature. 2000; PubMed Scopus Google Scholar). initial studies using calpain in a mouse model of AD showed an of cognitive function in that were with a calpain at an early S. S. J. Mol. Neurosci. 2003; PubMed Scopus Google Scholar). The mechanisms by Aβ the of this have not been elucidated. is a by in P. Biochem. Biophys. Res. Commun. 2004; PubMed Scopus Google Scholar). Thus, one mechanism of could the of The molecular mechanism by Aβ is to be this have been for membrane and M.P. K. I. J. Neurosci. 12: PubMed Google Scholar, A. E. R. I. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. J. 2003; PubMed Scopus Google Scholar). Our results obtained using cultured hippocampal neurons support the that Aβ also dynamin 1 expression. This Aβ-induced decrease in dynamin 1 might the of of the dynamin 1 gene is and the J. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). is by protein S. J. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). in the could have significant on the of dynamin 1 gene and synaptic for this has been provided by a study that Aβ protein and in cultured hippocampal neurons A. M. Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google Scholar). dynamin 1 levels were in the hippocampi of Tg2576 The results obtained using this AD animal model are in with a report an in dynamin 1 from brains of these (9Yao P.J. Zhu M. Pyun E.I. Brooks A.I. Therianos S. Meyers V.E. Coleman P.D. Neurobiol. Dis. 2003; 12: 97-109Crossref PubMed Scopus (193) Google Scholar). This between the of Aβ on the of dynamin 1 in neurons that develop in culture or in could be to mechanisms leading to an in dynamin 1 could be by the cleavage of this protein in Tg2576 These mechanisms might not play the leading to dynamin 1 cleavage the observed in cultured the in dynamin 1 observed in the hippocampal of the Tg2576 could be the result of of to It is that cells from the from our cultures from the of dynamin 1 in to the of the proteins present in these it is that our results obtained using cultured hippocampal neurons the decrease in dynamin 1 observed in the brains of AD patients (9Yao P.J. Zhu M. Pyun E.I. Brooks A.I. Therianos S. Meyers V.E. Coleman P.D. Neurobiol. Dis. 2003; 12: 97-109Crossref PubMed Scopus (193) Google Scholar). our results suggest that Aβ a decrease of dynamin 1 in hippocampal This on dynamin 1 is an early that synapse loss both in cultured hippocampal neurons and in hippocampal neurons obtained from Tg2576 These findings support a study that showed the decrease of dynamin 1 in AD brains (9Yao P.J. Zhu M. Pyun E.I. Brooks A.I. Therianos S. Meyers V.E. Coleman P.D. Neurobiol. Dis. 2003; 12: 97-109Crossref PubMed Scopus (193) Google Scholar). In addition, these results present a molecular for the cognitive decline in absence of synapse loss in the early stages of AD. The that are an for therapeutic is Thus, that calpain and/or protein targets to synaptic could therapeutic for AD. We and for We for the of a dynamin 1 We also for with