Drebrin Protein Research Articles

The actin binding protein drebrin helps to protect against the development of seizure-like events in the entorhinal cortex

The actin binding protein drebrin plays a key role in dendritic spine formation and synaptic plasticity. Decreased drebrin protein levels have been observed in temporal lobe epilepsy, suggesting the involvement of drebrin in the disease. Here we investigated the effect of drebrin knockout on physiological and pathophysiological neuronal network activities in mice by inducing gamma oscillations, involved in higher cognitive functions, and by analyzing pathophysiological epileptiform activity. We found that loss of drebrin increased the emergence of spontaneous gamma oscillations suggesting an increase in neuronal excitability when drebrin is absent. Further analysis showed that although the kainate-induced hippocampal gamma oscillations were unchanged in drebrin deficient mice, seizure like events measured in the entorhinal cortex appeared earlier and more frequently. The results suggest that while drebrin is not essential for normal physiological network activity, it helps to protect against the formation of seizure like activities during pathological conditions. The data indicate that targeting drebrin function could potentially be a preventive or therapeutic strategy for epilepsy treatment.

Lactobacillus rhamnosus GG and Bifidobacterium bifidum TMC3115 Can Affect Development of Hippocampal Neurons Cultured In Vitro in a Strain-Dependent Manner.

This study examined whether Lactobacillus rhamnosus GG (LGG) and Bifidobacterium bifidum TMC3115 (TMC3115) could morphologically or physiologically influence hippocampal neuronal development in vitro. Hippocampal neurons cultured in vitro were exposed to live or heat-inactivated LGG or TMC3115 for either 6 or 24h. Neuronal morphological changes and drebrin (DRB) and synaptophysin (SYP) protein levels were monitored using immunofluorescence. And the levels of DRB, SYP, and brain-derived neurotrophic factor (BDNF), and cAMP-response element binding protein (CREB) mRNA were detected using RT-PCR. The BDNF, CREB, and phosphorylated-CREB (P-CREB) protein levels were detected by extraction-enzyme-linked immunosorbent assay (ELISA) or Western blot assays. Heat-inactivated LGG and TMC3115 could enhance neuron viability, DRB and SYP protein levels, and BDNF mRNA level were significantly altered after exposure to the tested bacteria with 6h or 24h. There were no significant differences in neuronal morphology or DRB, SYP, or CREB mRNA levels among the groups following bacterial exposure. However, following exposure of live TMC3115 for 24h, the neuronal BDNF and P-CREB protein levels were both significantly up-regulated as detected by western blot assays. These results demonstrated that LGG and TMC3115 could affect neuronal viability, along with hippocampal synaptic and functional development, in a strain-dependent manner, which may also be closely associated with the physiological and culture conditions of each strain. Up-regulated P-CREB may be one of the underlying mechanisms by which the bacteria, especially neurons following exposure of live TMC3115 for 24h, are able to regulate neuronal BDNF protein production.

Elevated Plasma Levels of Drebrin in Glaucoma Patients With Neurodegeneration.

Glaucoma is an optic neuropathy characterized by progressive degeneration of retinal ganglion cells (RGCs). Aberrations in several cytoskeletal proteins, such as tau have been implicated in the pathogenesis of neurodegenerative diseases, could be initiating factors in glaucoma progression and occurring prior to axon degeneration. Developmentally regulated brain protein (Drebrin or DBN1) is an evolutionarily conserved actin-binding protein playing a prominent role in neurons and is implicated in neurodegenerative diseases. However, the relationship between circulating DBN1 levels and RGC degeneration in glaucoma patients remains unclear. In our preliminary study, we detected drebrin protein in the plasma of glaucoma patients using proteomic analysis. Subsequently, we recruited a total of 232 patients including primary angle-closure glaucoma (PACG), primary open-angle glaucoma (POAG) and Posner-Schlossman syndrome (PS) and measured its DBN1 plasma levels. We observed elevated DBN1 plasma levels in patients with primary glaucoma but not in patients with PS compared to nonaxonopathic controls. Interestingly, in contrast to tau plasma levels increased in all groups of patients, elevated drebrin plasma levels correlated with retinal nerve fiber layer defect (RNFLD) in glaucoma patients. To further explore the expression of DBN1 in neurodegeneration, we conducted experiment of optic nerve crush (ONC) models, and observed increased expression of DBN1 in the serum as well as in the retina and then decreased after ONC. This result reinforces the potentiality of circulating DBN1 levels are increased in glaucoma patients with neurodegeneration. Taken together, our findings suggest that circulating DBN1 levels correlated with RNFLD and may reflect the severity of RGCs injury in glaucoma patients. Combining measurement of circulating drebrin and tau levels may be a useful indicator for monitoring progression of neurodegenerative diseases.

Isoform-dependent Regulation of Drebrin Dynamics in Dendritic Spines

Dendritic spines have stable filamentous actin (F-actin) and dynamic F-actin. The formation of stable F-actin plays a pivotal role in spine formation. Drebrin binds to and stabilizes F-actin in dendritic spines. Interestingly, the conversion of the drebrin E isoform to drebrin A occurs in parallel with synapse formation, suggesting that this conversion promotes synapse formation via F-actin accumulation. In this study, we measured the dynamics of GFP-tagged drebrin E (GFP-DE) and drebrin A (GFP-DA) in cultured hippocampal neurons by fluorescence recovery after photobleaching analysis. We found that GFP-DA has a larger stable fraction than GFP-DE. The stable drebrin fraction reflects its accumulation in dendritic spines, therefore the isoform conversion may increase the amount of stable F-actin in dendritic spines. The stable fraction was dependent on the drebrin A-specific sequence “Ins2”, located in the middle of the drebrin protein. In addition, F-actin depolymerization with latrunculin A significantly reduced the stable GFP-DA fraction. These findings indicate that preferential binding of drebrin A to F-actin than drebrin E causes higher stable fraction of drebrin A in dendritic spines, although the F-actin-binding ability of purified drebrin E and drebrin A are comparable. Therefore, we suggest that a drebrin isoform conversion from drebrin E to drebrin A in dendritic spines results in the accumulation of drebrin-bound stable F-actin, which plays a pivotal role in synapse formation.

Effective expression of Drebrin in hippocampus improves cognitive function and alleviates lesions of Alzheimer's disease in APP (swe)/PS1 (ΔE9) mice

Alzheimer's disease (AD), a progressive development dementia, is increasingly impacting patients' living conditions worldwide. Despite medical care and funding support, there are still no highly individualized drugs and practical strategies for clinical prevention and treatment. Developmentally regulated brain protein (abbreviated as Drebrin or Dbn, also known as Dbn1 in mouse) exists in neurons, especially in dendrites, and is an actin-binding protein that modulates synaptic morphology and long-term memory. However, the majority of previous studies have focused on its upstream proteins and neglected the impact Drebrin has on behavior and AD in vivo. Here, we tracked the behavioral performances of 4-, 8-, 12-, and 16-month-old AD mice and investigated the expression level of Drebrin in their hippocampi. A Pearson correlation analysis between Drebrin levels and behavioral data was performed. Subsequently, 2-month-old AD mice were injected with rAAV-zsGreen-Dbn1 vector, composing the APP/PS1-Dbn1 group, and sex- and age-matched AD mice were injected with rAAV-tdTomato vector to serve as the control group. All mice were conducted behavioral tests and molecular detection 6months later. (i) The expression of Drebrin is decreased in the hippocampus of aged AD mice compared with that of age-matched WT and young adult AD mice; (ii) cognitive ability of APP/PS1 mice decreases with age; (iii) Drebrin protein expression in the hippocampus correlates with behavioral performance in different aged AD mice; (iv) cognitive ability improved significantly in APP/PS1-Dbn1 mice; (v) the expression level of Drebrin in APP/PS1-Dbn1 mouse hippocampus was significantly increased; (vi) the pathological lesion of AD was alleviated in APP/PS1-Dbn1 mice; (vii) the filamentous actin (F-actin) and microtubule-associated protein 2(MAP-2) in APP/PS1-Dbn1 mice were notably more than control mice. In this study, an effective expression of Drebrin improves cognitive abilities and alleviates lesions in an AD mouse model. These results may provide some valid resources for therapy and research of AD.

Early growth response‐1‐mediated down‐regulation of drebrin correlates with loss of dendritic spines

Post-synaptic dendritic spines are structurally composed of actin cytoskeleton, which undergoes dynamic morphological changes to accommodate incoming synaptic activity. Drebrin is an actin-binding protein highly expressed in dendritic spines that serves an important role in regulating spine morphology. Functionally, loss of drebrin directly correlates with deficits in learning and memory, as is the case observed in Alzheimer's disease. Despite these findings, the regulatory factor responsible for drebrin loss remains unclear. Here, we show that early growth response-1 (Egr-1), an inducible zinc finger transcription factor, down-regulates drebrin expression. Chromatin immunoprecipitation analyses identified Egr-1 binding sites upstream of the drebrin start site in neuronal cells. Over-expression of Egr-1 invitro in primary hippocampal neurons or invivo in homogenates prepared from the hippocampi of an inducible mouse model of Egr-1 show reduced drebrin mRNA and protein levels. Conversely, increased drebrin was detected in hippocampal samples isolated from Egr-1-deficient brain. These data demonstrate that Egr-1 interacts with the drebrin promoter and negatively regulates drebrin expression. Furthermore, immunocytochemical and Golgi staining analyses revealed reduced drebrin protein and dendritic spine density as well as reduced expression of synaptic markers in invitro hippocampal neurons over-expressing Egr-1 and invivo inducible mouse model of Egr-1. In contrast, increased drebrin expression correlated with increased dendritic spine density was detected in samples from Egr-1-deficient mice. These data provide evidence that Egr-1 is a novel regulator of drebrin expression, which is linked to changes in dendritic spine density.

Investigation of hippocampal synaptic transmission and plasticity in mice deficient in the actin-binding protein Drebrin

The dynamic regulation of the actin cytoskeleton plays a key role in controlling the structure and function of synapses. It is vital for activity-dependent modulation of synaptic transmission and long-term changes in synaptic morphology associated with memory consolidation. Several regulators of actin dynamics at the synapse have been identified, of which a salient one is the postsynaptic actin stabilising protein Drebrin (DBN). It has been suggested that DBN modulates neurotransmission and changes in dendritic spine morphology associated with synaptic plasticity. Given that a decrease in DBN levels is correlated with cognitive deficits associated with ageing and dementia, it was hypothesised that DBN protein abundance instructs the integrity and function of synapses. We created a novel DBN deficient mouse line. Analysis of gross brain and neuronal morphology revealed no phenotype in the absence of DBN. Electrophysiological recordings in acute hippocampal slices and primary hippocampal neuronal cultures showed that basal synaptic transmission, and both long-term and homeostatic synaptic plasticity were unchanged, suggesting that loss of DBN is not sufficient in inducing synapse dysfunction. We propose that the overall lack of changes in synaptic function and plasticity in DBN deficient mice may indicate robust compensatory mechanisms that safeguard cytoskeleton dynamics at the synapse.

Molecular Cloning of Drebrin: Progress and Perspectives.

Chicken drebrin isoforms were first identified in the optic tectum of developing brain. Although the time course of protein expression was different in each drebrin isoform, the similarity between their protein structures was suggested by biochemical analysis of purified protein. To determine their protein structures, the cloning of drebrin cDNAs was conducted. Comparison between the cDNA sequences shows that all drebrin cDNAs are identical except that the internal insertion sequences are present or absent in their sequences. Chicken drebrin are now classified into three isoforms, namely, drebrins E1, E2, and A. Genomic cloning demonstrated that the three isoforms are generated by an alternative splicing of individual exons encoding the insertion sequences from single drebrin gene. The mechanism should be precisely regulated in cell-type-specific and developmental stage-specific fashion. Drebrin protein, which is well conserved in various vertebrate species, although mammalian drebrin has only two isoforms, namely, drebrin E and drebrin A, is different from chicken drebrin that has three isoforms. Drebrin belongs to an actin-depolymerizing factor homology (ADF-H) domain protein family. Besides the ADF-H domain, drebrin has other domains, including the actin-binding domain and Homer-binding motifs. Diversity of protein isoform and multiple domains of drebrin could interact differentially with the actin cytoskeleton and other intracellular proteins and regulate diverse cellular processes.

Do synaptic changes occur before old age in people at high genetic risk of Alzheimer's disease?

BackgroundPossession of an ɛ4 allele of the APOE gene is the main known genetic risk factor for late-onset Alzheimer's disease. Neuropathological changes of Alzheimer's disease can be found much earlier and are more pronounced in people with an ɛ4 allele than in those without this allele. When or how these changes begin are not known. We tested our hypothesis that ɛ4 allele possession in adults aged under 75 years is associated with alterations in concentrations of synaptic proteins. MethodsWe obtained samples from UK brain banks of superior temporal gyrus and hippocampus from 103 individuals aged 75 years or younger with no evidence of dementia. The proteins synaptophysin, PSD-95, drebrin, septin-7, and SNAP-25 were measured by ELISA and corresponding gene expression—SYP, DLG4, DBN1, SEPT7, and SNAP-25 with RT-PCR. APOE genotyping was performed by liquid phase two single nucleotide polymorphism genotyping. We corrected for neuronal content by ELISA measurement of neuron-specific enolase. Regression models controlled for important confounders. FindingsThere were five genotypes (one e22, 15 e32, 57 e33, 22 e34, five e44). The ɛ33 group was the reference group in all regressions. There was a significant increase in gene expression of SNAP-25 (difference between geometric means 0·2, p=0·038) and SYP (0·3, p=0·018) in the superior temporal gyrus in ɛ4 carriers but only a non-significant trend in the protein concentrations. Drebrin protein was increased in the hippocampi of the ɛ32 group (difference between means 3·4 ng/μL, p=0·019). There was a non-significant trend towards PSD-95 being increased in the hippocampus in the ɛ32 group (difference between means 0·6 ng/μL, p=0·079). Since each protein measure is a crude proxy measure of post-synaptic density and has measurement error, a summary z-score was also used. The summary score supported a per genotype difference in post-synaptic density in the hippocampus (difference from reference group 2·3, p=0·02). Expression of these genes was not increased in the ɛ32 group, but PSD-95 expression was increased in ɛ4 carriers (difference between geometric means 0·3, p=0·017) despite no protein differences. InterpretationOur finding that the ɛ32 group had an increase in post-synaptic proteins despite a lower risk of Alzheimer's disease than the other groups is intriguing. Low numbers in our study prevent a definitive conclusion, despite our procurement of tissue from multiple UK brain banks. FundingWellcome Trust Research Training Fellowship.

Experimental research on the effect of lateral ventricle transplantation of neurotrophic factor-transfected cells derived from Glia cell line on vascular dementia in rats

Objective To investigate the effect of lateral ventricle transplantation of neurotrophic factor-transfected cells derived from Glia cell line on vascular dementia in rats and gene expression of Drebrin in hippocampal region. Methods By using gene clone technique, the GDNF gene was transfected into SH-SY5Y cell lines. 104 adult male Sprague-Dawley rats weighing (200±20) gram were divided into groups: transplanted group, injected group, control group, all of which accepted operation by permanent ligation of left common carotid artery and clipping right common carotid artery repeatedly to build up model of vascular dementia, and sham operation group which accepted no ligation or clipping. 6 rats from each group were decapitated on the third day, seventh day and tenth day after transplanting treatment were for fluorescence detection. The rest 20 rats in each group were used to detect learning and memory functions by Morris water maze on the third day and decapitated on the fourth day after transplanting treatment. Then GDNF level in temporal lobe were detected by enzyme-linked immunosorbent assay (ELISA), while Drebrin mRNA and protein levels in hippocampal region were detected by real time-PCR and Westernblot respectively. Results There was strong fluorescent light detected around lateral ventricle of rats in transplanted group on the third day after transplantation, which faded on the seventh day and disappeared on the tenth day. The learning and memory functions of rats in transplanted group were improved significantly. The escape latency was shorter in transplanted group than in injected group and control group〔(34.89±4.15) s vs. (43.86±6.95) s, (50.89±3.66) s, both P<0.05〕, while shuttle times through the third quadrant were more often in transplanted group than in injected group and control group〔(11.00±1.49) vs. (9.26±1.38), (8.04±1.12), both P<0.05〕. GDNF level and Drebrin mRNA and protein levels were higher in transplanted group than in injected group and control group〔GDNF: (315.71±27.43) vs. (256.26±19.90), (141.95±21.33), Drebrin mRNA: (5.54±0.35) vs. (3.10±0.33), (1.32±0.23), Drebrin protein: (0.55±0.05) vs. (0.43±0.06), (0.26±0.06), all P<0.05〕. Conclusions GDNF-transfected cells could survive in the lateral cerebral ventricle of rats for about seven days. The method for treating vascular dementia through the technique of transplanting GDNF-transfected cells is certain feasible, which has a better therapeutic effect than GDNF-injection directly into lateral cerebral ventricle. The therapeutic effect of GDNF on vascular dementia may be related to its action of regulating neural plasticity. Key words: Glial cell line-derived neurotrophic factor; Dementia, vascular; Trans-plantation

Ameliorative effects of physcion 8-O-β-glucopyranoside isolated from Polygonum cuspidatum on learning and memory in dementia rats induced by Aβ1–40

Context: Polygonum cuspidatum Sieb. Et Zucc. (Polygonaceae) has been traditionally used in folk medicine to treat various diseases.Objective: This study investigates the ameliorative effects of physcion 8-O-β-glucopyranoside (PSG) isolated from P. cuspidatum on learning and memory in dementia rats induced by Aβ1–40.Materials and methods: Dementia rats were prepared by intracerebroventricular injection of Aβ1–40. PSG (5, 10, 20, and 40 mg/kg/d, for 5 d) was administered orally. Ameliorative activity of PSG in dementia rats was evaluated by the Morris water maze (MWM) test, and its mechanisms were explored by evaluating AchE activity, levels of DA, NE, and 5-HT in hippocampus, and drebrin protein expressions in hippocampus.Results: Our results indicated that PSG (5, 10, 20, and 40 mg/kg/d) significantly inhibited the prolonged latency in dementia rats (p < 0.05), and inhibitory rates were 16.5, 22.7, 33.0, and 44.8% after 5 d of learning, indicating that PSG improves learning and memory of dementia rats. Furthermore, PSG significantly decreased AchE activity (10, 20, and 40 mg/kg/d; p < 0.05), increased 5-HT (20 and 40 mg/kg/d, p < 0.05), NE (10, 20, and 40 mg/kg/d; p < 0.05), and DA levels (5, 10, 20, and 40 mg/kg; p < 0.05) in the hippocampus. Additionally, PSG obviously decreased the Aβ contents in hippocampus (10, 20, and 40 mg/kg/d; p < 0.05), and up-regulated drebrin protein expressions (5, 10, 20, and 40 mg/kg/d; p < 0.05).Conclusions: PSG can significantly enhance learning and memory in Aβ1–40-induced dementia rats, and the mechanisms may be related to increase levels of Ach, 5-HT, NE, and DA, decrease Aβ contents, and up-regulation of drebrin proteins in hippocampus.

P4‐031: Suppression of drebrin gene expression causes Alzheimer's‐like synapse loss in primary hippocampal neurons in culture

Alzheimer's disease (AD) is characterized by the progressive neuronal and synapse loss in brain regions associated with cognitive dysfunction as well as the deposition of amyloid plaques and neurofibrillary tangles. Synapse loss occurs early in the pathogenesis of AD and is regarded as the basis of dementia as observed in both patients and related transgenic mouse models. Therefore, restoration, prevention and/or reduction of synapse loss represents a major therapeutic target for AD. Excitatory (glutamatergic) synapses are formed between presynaptic axon terminals and highly specialized protrusions on the postsynaptic dendrites known as dendritic spines. In AD, a significant reduction of spine density and number has been observed. Filamentous actin (F-actin) is the major structural element of dendritic spines. Drebrin, a neuron-specific F-actin binding protein, is concentrated in dendritic spines and is known to play a role in dendritic spine morphology via modulation of actin dynamics. In AD, a significant downregulation of drebrin has been observed. Loss of drebrin has been suggested to destabilize actin cytoskeleton leading to dendritic pathology. The mechanism responsible for drebrin loss remains to be elucidated. Western blotting analysis has been used to measure drebrin protein level in Egr-1 KO mice as well primary hippocampal nuerons overexpressing Egr-1 via lentivirus-mediated infection. Drebrin mRNA level in primary hippocampal neurons was measured using qRT-PCR. In this study, we have found significant elevation of drebrin protein level in mice brain deficient in Early Growth Response 1 (Egr-1) transcription factor known to be upregulated in AD brain. When overexpression in primary hippocampal neurons in culture, Egr-1 causes reduction in drebrin level and decrease in the number of dendritic spines. In silico RVista analysis revealed three putative Egr-1 binding sites within the drebrin promoter. In vitro qRT-PCR showed a dose-dependent decrease of drebrin mRNA level in Egr-1 overexpressing neurons. Our data demonstrate that Egr-1 is an in vivo transcription suppressor of drebrin gene expression and suggest that Egr-1 plays a role in AD synaptic pathology by reducing drebrin level in the brain.

Chemico-genetic identification of drebrin as a regulator of calcium responses

Store-operated calcium channels are plasma membrane Ca2+ channels that are activated by depletion of intracellular Ca2+ stores, resulting in an increase in intracellular Ca2+ concentration, which is maintained for prolonged periods in some cell types. Increases in intracellular Ca2+ concentration serve as signals that activate a number of cellular processes, however, little is known about the regulation of these channels. We have characterized the immuno-suppressant compound BTP, which blocks store-operated channel mediated calcium influx into cells. Using an affinity purification scheme to identify potential targets of BTP, we identified the actin reorganizing protein, drebrin, and demonstrated that loss of drebrin protein expression prevents store-operated channel mediated Ca2+ entry, similar to BTP treatment. BTP also blocks actin rearrangements induced by drebrin. While actin cytoskeletal reorganization has been implicated in store-operated calcium channel regulation, little is known about actin-binding proteins that are involved in this process, or how actin regulates channel function. The identification of drebrin as a mediator of this process should provide new insight into the interaction between actin rearrangement and store-operated channel mediated calcium influx.

Decreased drebrin mRNA expression in Alzheimer disease: Correlation with tau pathology

To investigate the mRNA expression of the dendritic spine protein drebrin in Alzheimer's disease (AD), we performed post-mortem in situ hybridization studies in brain sections from 20 AD patients and 21 controls. AD diagnosis was confirmed by decreased drebrin protein and increased Abeta(40) (+464%; P < 0.05), Abeta(42) (+369%; P < 0.0001), Abeta(42/40) ratio (+226%; P < 0.01), total tau (+2,725%; P < 0.0001), and paired helical filament tau (PHFtau; +867%; P < 0.001) compared with controls. We found significant decreases in drebrin mRNA in the parietal cortex (-27%; P < 0.01), the temporal cortex (-22%; P < 0.05), and the hippocampus (-25%; P < 0.05) of AD patients compared with controls. Cortical levels of drebrin mRNA correlated positively with soluble total tau (r(2) = +0.244) but negatively with duration of symptoms (r(2) = -0.357) and PHFtau (r(2) = -0.248). Drebrin mRNA levels were correlated to a lesser degree with the drebrin protein content (r(2) = +0.136) and with sim2 (r(2) = +0.176), a potential modulator of drebrin transcription. Our results suggest that the down-regulation of drebrin mRNA expression plays an important role in AD and is closely related to the progression of the disease.

Isoform specific expression of the neuronal F-actin binding protein, drebrin, in specialized cells of stomach and kidney epithelia.

To further understand the functional role that the F-actin binding protein, drebrin (developmentally regulated brain protein), plays in the regulation of F-actin, we characterized its expression in non-neuronal cells. Using nanoelectrospray mass spectrometry methods, we initially identified drebrin in non-neuronal cultured cells. Using a drebrin-specific monoclonal antibody, we were able to detect drebrin protein in several different cell lines derived from fibroblasts, astrocytomas, and simple epithelia, but not in cell lines derived from stratified epithelia. Double-label immunofluorescence experiments of cultured cell monolayers revealed the localization of drebrin at the apical plasma membrane together with a pool of submembranous F-actin. Immunoblot analysis of mouse organs revealed that, in addition to its high levels of expression in brain, drebrin was present in stomach and to a lesser degree in kidney, colon, and urinary bladder. Drebrin protein detected in the non-brain organs migrated faster through SDS-PAGE gels, indicating that the lower molecular weight embryonic brain isoform (E2) may be the prominent isoform in these organs. RT-PCR experiments confirmed the specific expression of the E2 isoform in adult stomach, kidney, and cultured cells. In situ immunofluorescence experiments revealed a cell-type specific pattern in both stomach and kidney. In stomach, drebrin was specifically expressed in the acid-secreting parietal cells of the fundic glands, where it accumulated at the extended apical membrane of the canaliculi. In kidney, drebrin was expressed in acid-secreting type A intercalated cells, where it localized specifically to the apical plasma membrane. Drebrin was expressed as well in the distal tubule epithelial cells where the protein was concentrated at the luminal surface and present at the interdigitations of the basolateral membranes.

Molecular-Cloning of cDNA Encoding Human Drebrin E and Chromosomal Mapping of Its Gene

Drebrins are novel actin-binding proteins in the brain which are developmentally regulated. Three isoforms: two embryonic types (El and E2) and an adult type (A) are generated by alternative RNA splicing from a single drebrin gene in the chicken brain. A full length cDNA clone of human drebrin E has been isolated from a cDNA library of human fetus brain. The clone is 2596 base pairs in length and contains an open reading frame of 1947 nucleotides encoding a protein of 649 amino acids. The deduced amino acid sequence, except for the internal 138-nucleotide sequence (ins2), exhibits 88% homology with rat drebrin A. Spot blot hybridization using flow-sorted human chromosomes provides evidence that the gene encoding human drebrin protein locates on human chromosome 5.

Changes of drebrin protein in subcellular localization induced by neuronal differentiation

Changes of drebrin protein in subcellular localization induced by neuronal differentiation