The Par polarity complex consisting of the evolutionarily conserved proteins mPar3, mPar6, and aPKC regulates cell polarity in many cell types including neurons. Here we show that mPar3 is required for the establishment of neuronal polarity and links the Smurf2 to Kinesin-2. The HECT domain E3 ubiquitin ligase Smurf2 ensures that neurons extend only a single axon by initiating the degradation of inactive Rap1B through the ubiquitin/ proteasome system. Its interaction with mPar3 is required to localize Smurf2 to growth cones and restrict Rap1B to the axon. Interfering with the binding of mPar3 to Kinesin-2 or Smurf2 to mPar3 and knockdown of mPar3 by RNAi disrupt the establishment of neuronal polarity through the failure to restrict Rap1B to a single neurite.During the differentiation of hippocampal neurons, unpolarized cells initially form several equivalent neurites, all of which have the potential to become an axon (stage 2) (1). Neuronal polarity is established when one of these is selected as the axon (stage 3) by a signaling pathway that includes PI3K, 4 the GTPases Rap1B, Cdc42, and Rac, the Par polarity complex, and GSK3␤ (2-8). The Par complex consisting of mPar3, mPar6, and aPKCs (PKC and PKC) plays an essential role in determining polarity in many cell types (9). mPar3 promotes axon extension downstream of Cdc42 through the STEF-dependent activation of Rac and the stimulation of aPKC. mPar6 interacts specifically with GTP-bound Cdc42 and Rac1 (10, 11). Binding of Cdc42 enhances the activity of mPar6-associated aPKCs (11,12). In addition, mPar3 interacts with the Rac-specific guanine nucleotide-exchange factors (GEFs) STEF and Tiam1 to control tight junction assembly and to mediate the activation of Rac by Cdc42 through the Par complex to promote axon growth (5,13,14). In neurons, mPar3 and mPar6 are present in all processes of non-polarized stage 2 neurons and become restricted to the axon of polarized stage 3 neurons (6, 7). Overexpression of mPar3 or mPar6 disrupts neuronal polarity and induces the extension of several long but Tau-1 negative processes instead of a single axon (4, 7). The mPar3 C terminus interacts with the Kinesin-2 subunit KIF3A (4). This interaction is essential for the transport of mPar3 and aPKCs into neurites and the establishment of neuronal polarity.We have shown that the sequential activity of the GTPases Rap1B and Cdc42 directs the establishment of polarity in hippocampal neurons downstream of PI3K (6). Initially, Rap1B is present at the tips of all neurites of unpolarized stage 2 neurons but, concomitant with the appearance of mPar3 in all processes, is restricted to a single neurite before the axon becomes distinguishable, and the Par complex is localized exclusively to the axon (6, 7). Rap1B is necessary and sufficient to specify axonal identity. Therefore, the restriction of Rap1B to a single neurite is an essential step in the establishment of neuronal polarity. This restriction is mediated by the selective degradation of Rap1B by the UPS and prevents the formation of ...

The Aurora kinases are a family of serine/threonine protein kinases that perform important functions during the cell cycle. Recently, it was shown that Drosophila Aurora A also regulates the asymmetric localization of Numb to the basal and the partitioning-defective (Par) complex to the apical cortex of neuroblasts by phosphorylating Par6. Here, we show that Aurora A is required for neuronal polarity. Suppression of Aurora A by RNA interference results in the loss of neuronal polarity. Aurora A interacts directly with the atypical protein kinase C binding domain of Par3 and phosphorylates it at serine 962. The phosphorylation of Par3 at serine 962 contributes to its function in the establishment of neuronal polarity.

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Nonenzymatic glycation results in the formation of advanced glycation end products (AGEs) through a nonenzymatic multistep reaction of reducing sugars with proteins. AGEs have been suspected to be involved in the pathogenesis of several chronic clinical neurodegenerative complications including Alzheimer's disease, which is characterized with the activation of microglial cells in neuritic plaques. To find out the consequence of this activation on microglial cells, we treated the cultured microglial cells with different glycation levels of Bovine Serum Albumin (BSA) which were prepared in vitro. Extent of glycation of protein has been characterized during 16 weeks of incubation with glucose. Treatment of microglial cells with various levels of glycated albumin induced nitric oxide (NO) production and consequently cell death. We also tried to find out the mode of death in AGE-activated microglial cells. Altogether, our results suggest that AGE treatment causes microglia to undergo NO-mediated apoptotic and necrotic cell death in short term and long term, respectively. NO production is a consequence of iNOS expression in a JNK dependent RAGE signalling after activation of RAGE by AGE-BSA.

Alteration in the expression level of peripheral myelin protein 22 (PMP22) is the most frequent cause for demyelinating neuropathies of Charcot‐Marie‐Tooth type. Here, we demonstrate a loss of motoneurons (MNs) in the spinal cords from transgenic mice over‐expressing Pmp22 (Pmp22tg) while mice lacking Pmp22 [Pmp22ko; knockout (ko)] exhibited normal MN numbers at the symptomatic age of 60 days. In order to describe the molecular changes in affected MNs, these cells were isolated from lumbar spinal cords by laser‐capture microdissection. Remarkably, the MNs of the Pmp22ko and Pmp22tg mice showed different expression profiles because of the altered Pmp22 expression. The changes in the expression profile of MNs from Pmp22ko mice resemble those described in MNs from mice after nerve injury and included genes that had been described in neuronal growth and regeneration like Gap43 and Sprr11a. The changes detected in the expression pattern of MNs from Pmp22tg mice exhibited fewer similarities to other expression patterns. The specific expression pattern in the MNs of the Pmp22ko mice might contribute to the better survival of the MNs. Our study also revealed induction of genes like brain‐expressed X‐linked 1 (Bex1) and desmoplakin (Dsp) that had recently been found up‐regulated in MNs of human amyotrophic lateral sclerosis patients.

Breast cancer (BC) is the most common malignancy in women with 18% prevalence and 1 million new cases each year. This cancer showed the highest mortality in the United States and claimed a mortality rate of 89.2 per 100,000 in the world in 2000 (Aurit, Devesa, Soliman, & Schairer, 2019). BC tumors present a heterogeneous phenotype regarding the expressions of different cellular receptors (estrogen receptors [ER], progesterone receptor [PR], and epidermal growth factor receptor 2 [HER2]) in tumor cells. Studies

Protein glycation has been implicated to play an important role in the pathogenesis of Alzheimer's disease and other neurological disorders. Glycation induces extensive change in the structure of proteins and leads to the formation of cross beta-structures which are detected by the receptor of AGE. Activation of these receptors by glycated proteins transduces the signaling pathways which contribute to neuronal malfunctions and death. Glycated proteins can induce activation of microglia, which exacerbate the pathology of Alzheimer's disease by causing chronic inflammation. Compounds which can decelerate glycation or prevent the structural change of proteins during glycation should be of therapeutic interest. In this study the effect of nicotine on protein glycation and structural alterations of the glycated protein were investigated. Bovine serum albumin, as a model protein, was glycated by glucose in the presence or absence of nicotine and structural changes in the protein together with the effect of glycated proteins on the activation of microglia via receptor of AGE were studied. Nicotine not only could not prevent glycation, but even increased protein glycation. However, proteins glycated in the presence of nicotine did not form beta-structures. In the absence of this secondary structure glycated proteins cannot bind to the receptor of AGE on microglia. Here we showed that glycated proteins prepared in the presence of nicotine could not activate microglial cells.

Therapeutic strategies against triple‐negative breast cancer (TNBC) are associated with drug‐induced toxicities. The tropical edible red clover (Trifolium pratense L.) is rich in polyphenolic compounds which confer the plant potential anticancer properties. The aim of this study was to investigate the effects of T. pratense and doxorubicin (DOX) on the apoptosis and proliferation of 4T1 tumor cells in an allograft model of tumor‐bearing BALB/c mice. Fifty‐six female 4T1‐tumor bearing‐ BALB/c mice were randomly divided into 7 groups (n = 8/group) to receive different doses and combinations of DOX and T. pratense extract for 35 days. On the 36th day, serum estradiol (E2), IL‐12 and IFN‐γ cytokines, and glutathione peroxidase (GPx) activity were measured. Tumor's ferric reducing antioxidant power (FRAP) and the expressions of apoptosis‐related genes (p53, Bax, Bcl‐2, and caspase‐3) were also evaluated. Immunohistochemical staining for Ki‐67 and p53 were performed. Our results showed that the co‐treatment of DOX and T. pratense (100–400 mg/kg) inhibited the proliferation of 4T1 tumor cells in dose‐ and time‐dependent manners. The co‐treatment of DOX and T. pratense (especially at the dose of 400 mg/kg) decreased the serum level of E2 (as a stimulant for breast tumor growth) and increased the serum levels of IL‐12 and IFN‐γ along with significant increments in serum GPx and tumor FRAP activities. The co‐administration of DOX and T. pratense also decreased the expression of Ki‐67 proliferation marker and increased the number p53 positive (i.e., apoptotic) cells within tumors. This was accompanied with the upregulation of pro‐apoptotic and down‐regulation of antiapoptotic genes. The key findings indicated the synergistic effects of DOX and T. pratense against TNBC xenografts.