Rab6 regulates transport and targeting of exocytotic carriers.
ABSTRACT Constitutive exocytosis delivers newly synthesized proteins, lipids, and other molecules from the Golgi apparatus to the cell surface. This process is mediated by vesicles, which bud off the trans-Golgi network, move along cytoskeletal filaments, and fuse with the plasma membrane. Here, we show that the small GTPase Rab6 marks exocytotic vesicles and, together with the microtubule plus-end-directed motor kinesin-1, stimulates their processive microtubule-based transport to the cell periphery. Furthermore, Rab6 directs targeting of secretory vesicles to plasma-membrane sites enriched in the cortical protein ELKS, a known Rab6 binding partner. Our data demonstrate that although Rab6 is not essential for secretion, it controls the organization of exocytosis within the cellular space.
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ABSTRACT: AVL9, DENND5A and NUPL1 are among the cancer driver candidate genes previously identified via dog-human comparison, and may function in epithelial cell polarity as indicated by bioinformatics analysis. To better understand their cellular functions and roles in cancer, we knocked down each gene in MDCKII cells through shRNA and performed three-dimensional culture. Compared to the control, the knockdown clones developed significantly more abnormal cysts, e.g., cysts with the lumen harboring dead and/or live cells, or cysts having multiple lumens. Further analysis revealed that abnormalities initiated at the first cell division and persisted throughout the entire cystogenesis process. For NUPL1-knockdown cells, abnormal cytogenesis largely arose from faulty cell divisions, notably monopolar spindles or spindles with poorly separated poles. For AVL9- or DENND5A-knockdown cells, abnormalities originated from both aberrant intracellular trafficking and defective mitosis. Moreover, while all knockdown clones displayed an accelerated rate of both cell proliferation and death, only AVL9- and DENND5A-knockdowns, but not NUPL1-knockdown, promoted cell migration. These observations indicate that NUPL1 contributes to bipolar spindle formation, whereas AVL9 and DENND5A participate in both intracellular trafficking and cell cycle progression. Our study shed lights on these genes' normal cellular functions and on how their alteration contributes to carcinogenesis.
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ABSTRACT: Transcranial magnetic stimulation (TMS) is a non invasive technique of brain stimulation which could be an interesting therapeutic tool in addictive disorders, being offline repetitive TMS (rTMS) the main strategy used due to it allows to disrupt underlying brain areas and examine behavioral consequences, (Knoch et al., 2006).There are some evidences that rTMS over the dorso-lateral prefrontal (DLPF) cortex is effective reducing craving in several drugs, such as cocaine, tobacco and alcohol (Camprodon et al., 2007; Amiaz et al., 2009; Mishra et al. 2010). In fact, a decrease on cocaine craving could be observed with a single session of rTMS. Complementary, the application of single and paired-pulse TMS in controlled paradigms is a novel and promising strategy in this area: recent results showed that reward modulated TMS-induced motor-evoked potentials, showing greater cortical inhibition during reward expectation (Gupta and Aron, 2010).Regarding alcohol abuse, there is a narrow relation between alcohol consumption and impulsiveness. On one hand, alcohol consumption produces impulsive behavior and desinhibition (Marinkovic et al. 2011); and on the other hand, impulsiveness personality trait predisposes to abusive alcohol consumption (Magid et al. 2007).Considering these evidences and the effectiveness of rTMS as therapeutic tool, use rTMS to reduce impulsivity could be a new approach to alcohol disorders treatment. Prefrontal cortex is a good candidate for this purpose since its pivotal role in impulsiveness behavior (Crews and Boettinger, 2009). Thus, we suggest that high frequency rTMS stimulation could improve the ability of alcohol abusers for control their drinking impulse.European Psychiatry 01/2012; 27:1. DOI:10.1016/S0924-9338(12)74247-5 · 3.21 Impact Factor
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ABSTRACT: A hallmark of the neuromuscular junction (NMJ) is the high density of acetylcholine receptors (AChRs) in the postsynaptic muscle membrane. The postsynaptic apparatus of the NMJ is organized by agrin secreted from motor neurons. The mechanisms that underlie the focal delivery of AChRs to the adult NMJ are not yet understood in detail. We previously showed that microtubule (MT) capture by the plus-end tracking protein CLASP2 regulates AChR density at agrin-induced AChR clusters in cultured myotubes via PI3 kinase acting through GSK3β. Here, we show that knock-down of the CLASP2-interaction partner LL5β by RNAi and forced expression of a CLASP2 fragment blocking the CLASP2/LL5β interaction inhibit microtubule capture. The same treatments impair focal vesicle delivery to the clusters. Consistent with these findings, knock-down of LL5β at the NMJ in vivo reduces the density and insertion of AChRs into the postsynaptic membrane. MT capturing and focal vesicle delivery to agrin-induced AChR clusters are also inhibited by microtubule and actin depolymerizing drugs, invoking both cytoskeletal systems in MT capture and in the fusion of AChR vesicles with the cluster membrane. Combined our data identify a transport system, organized by agrin through PI3 kinase, GSK3β, CLASP2 and LL5β, for precise delivery of AChR vesicles from the subsynaptic nuclei to the overlying synaptic membrane. © 2015 by The American Society for Cell Biology.