Rab11 and Its Role in Neurodegenerative Diseases.

Vesicles mediate the trafficking of membranes/proteins in the endocytic and secretory pathways. These pathways are regulated by small GTPases of the Rab family. Rab proteins belong to the Ras superfamily of GTPases, which are significantly involved in various intracellular trafficking and signaling processes in the nervous system. Rab11 is known to play a key role especially in recycling many proteins, including receptors important for signal transduction and preservation of functional activities of nerve cells. Rab11 activity is controlled by GEFs (guanine exchange factors) and GAPs (GTPase activating proteins), which regulate its function through modulating GTP/GDP exchange and the intrinsic GTPase activity, respectively. Rab11 is involved in the transport of several growth factor molecules important for the development and repair of neurons. Overexpression of Rab11 has been shown to significantly enhance vesicle trafficking. On the other hand, a reduced expression of Rab11 was observed in several neurodegenerative diseases. Current evidence appears to support the notion that Rab11 and its cognate proteins may be potential targets for therapeutic intervention. In this review, we briefly discuss the function of Rab11 and its related interaction partners in intracellular pathways that may be involved in neurodegenerative processes.

Trappc9 deficiency in mice impairs learning and memory by causing imbalance of dopamine D1 and D2 neurons.

Genetic mutations in the gene encoding transport protein particle complex 9 (trappc9), a subunit of TRAPP that acts as a guanine nucleotide exchange factor for rab proteins, cause intellectual disability with brain structural malformations by elusive mechanisms. Here, we report that trappc9-deficient mice exhibit a broad range of behavioral deficits and postnatal delay in growth of the brain. Contrary to volume decline of various brain structures, the striatum of trappc9 null mice was enlarged. An imbalance existed between dopamine D1 and D2 receptor containing neurons in the brain of trappc9-deficient mice; pharmacological manipulation of dopamine receptors improved performances of trappc9 null mice to levels of wild-type mice on cognitive tasks. Loss of trappc9 compromised the activation of rab11 in the brain and resulted in retardation of endocytic receptor recycling in neurons. Our study elicits a pathogenic mechanism and a potential treatment for trappc9-linked disorders including intellectual disability.

Amyloid-ß1-42 dynamically regulates the migration of neural stem/progenitor cells via MAPK-ERK pathway.

Neural stem/progenitor cell (NSPC) based therapy represents an attractive treatment for Alzheimer's disease (AD), the most common neurodegenerative disorder with no effective treatment to date. This can be achieved by stimulating endogenous NSPCs and/or administrating exogenously produced NSPCs. Successful repair requires the migration of NSPCs to the loci where neuronal loss occurs, differentiation and integration into neural networks. However, the progressive loss of neurons in the brain of AD patients suggests that the repair by endogenous NSPCs in the setting of AD may be defective. The production and deposition of amyloid-ß1-42 (Aß1-42) peptides is thought to be a central event in the pathogenesis of AD. Here we report that Aß1-42 peptides inhibit the migration of in vitro cultured NSPCs by disturbing the ERK-MAPK signal pathway. We found that the migratory capacity of NSPCs was compromised upon treatment with oligomeric Aß1-42; the inhibitory effect occurred in a dose-dependent manner. Our previous studies have shown that Aß1-42 triggers the expression of GRK2 by unknown mechanism. Herein we found that the Aß1-42 evoked upregulation of GRK2 expression was attenuated upon treatment with the ERK inhibitor SCH772984 at 2.5 µM, but not with inhibitors for p38 or JNK. We detected a dose-dependent increase in levels of phosphorylated ERK1/2 after incubation of cells with oligomeric Aß1-42 peptides for 3 days. We observed that an increase in the phosphorylation of p38 and JNK coincided with reduced phosphorylation of ERK1/2 upon treatment with Aß1-42 for 6 and/or 9 days. We hypothesize that the divergence of the activation of the MAPK family of pathways may contribute to the inhibition of NSPCs migration after the long-term incubation with Aß1-42. Pretreatment with 1  µM MEK inhibitor U0126 reversed the effects of Aß1-42 on GRK2 expression of and NSPC migration. Together, our results suggest that Aß1-42 oligomers compromise the migratory capacity of NSPCs through the MEK-ERK pathway.

The Landscape of Protein Tyrosine Phosphatase (Shp2) and Cancer.

Role of Shp2: The dysregulation of cell signaling cascades associated with the cell differentiation and growth, due to the deletion, insertion or point mutation in specific amino acids which alters the intrinsic conformation of the protein, can ultimately lead to a fatal cancer disease. The protein tyrosine phosphatase has been recognized as a key regulator of extracellular stimuli such as cytokine receptor and receptor tyrosine kinase signaling. In the last era, the PTPN11 gene (encode a Shp2 protein) and its association with acute myeloid, juvenile myelomonocytic, and B-cell acute lymphoblastic leukemia, Noonan syndrome, and myelodysplastic have been recognized as the cause of such deadly disease due to the occurrence of germline mutations in the interface of PTP and SH2 domain. Conclusion: The current study was designed to focus on the allosteric regulation (autoinhibition) of the of Shp2 protein. Subsequently, it will cover the last 10-year recap of Shp2 protein, their role in cancer, and regulation in numerous ways (allosteric regulation).