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Results for “Small interfering RNA”

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At least 595 records · Page 33Linked to original sources

PubMed2006

Aquaporin-1 transports NO across cell membranes.

NO plays a role in the regulation of blood pressure through its effects on renal, cardiovascular, and central nervous system function. It is generally thought to freely diffuse through cell membranes without need for a specific transporter. The water channel aquaporin-1 transports low molecular weight gases in addition to water and is expressed in cells that produce or are the targets of NO. Consequently, we tested the hypothesis that aquaporin-1 transports NO. In cells expressing aquaporin-1, NO permeability correlated with water permeability. NO transport was reduced by 71% by HgCl2, an inhibitor of aquaporin-1. Transport of NO by aquaporin-1 saturated at 3 micromol/L NO and displayed a K(1/2) (the concentration of NO that produces half of the maximum transport rate) of 0.54 micromol/L. Reconstitution of purified aquaporin-1 into lipid vesicles increased NO influx by 316%. In endothelial cells, lowering aquaporin-1 expression with a small interfering RNA (siRNA) blunted aquaporin-1 expression by 54% and NO release by 44%. We conclude that NO transport by aquaporin-1 may allow cells to control intracellular NO levels and effects. NO transport by aquaporin-1 may play a role in central nervous system, vascular and renal function, and consequently blood pressure. Disruption of NO transport by aquaporin-1 offers an alternate cause for diseases currently explained by inadequate NO bioavailability.

Animals↗

PubMed2006

Downregulation of SnoN expression in obstructive nephropathy is mediated by an enhanced ubiquitin-dependent degradation.

Smad transcriptional co-repressor SnoN acts as an antagonist that tightly controls the trans-activation of TGF-beta/Smad target genes. SnoN protein is reduced progressively in the fibrotic kidney after obstructive injury, suggesting that the loss of Smad antagonist is a critical event that leads to an uncontrolled fibrogenic signaling. However, the mechanism underlying SnoN downregulation remains unknown. This study investigated the regulation and mechanism of renal SnoN expression in vivo. Whereas SnoN protein was markedly diminished, its mRNA levels remained relatively constant in the obstructed kidney after ureteral ligation. An increased ubiquitination and proteasome-dependent degradation of SnoN was found in obstructed kidney, compared with sham controls. Smad ubiquitination regulatory factor-2, an E3 ubiquitin ligase, was induced and formed a complex with SnoN in vivo. In vitro, TGF-beta1 promoted SnoN protein degradation, which was mediated by ubiquitination and a proteasome-dependent mechanism. SnoN constitutively interacted with another Smad co-repressor, Ski, and they formed ternary complex with Smad2/3 upon TGF-beta1 stimulation. However, ectopic expression of Ski did not alter the degradation rate of SnoN. Blockage of SnoN degradation by proteasome inhibitor abolished TGF-beta1-mediated alpha-smooth muscle actin and fibronectin induction, suggesting that SnoN degradation could be necessary for TGF-beta1 to exert its fibrogenic action. Furthermore, knockdown of Smad ubiquitination regulatory factor-2 expression by small interfering RNA strategy led to an increase in SnoN abundance and inhibited the TGF-beta1-mediated gene transcription. These results indicate that downregulation of SnoN expression in the obstructed kidney is mediated by an enhanced ubiquitin-dependent degradation. Preservation of SnoN by inhibiting its degradation may be a novel strategy for targeting hyperactive Smad signaling in renal fibrotic diseases.

Actins↗

PubMed2005

Blockage of NF-kappaB induces serine 15 phosphorylation of mutant p53 by JNK kinase in prostate cancer cells.

The p53 tumor suppressor gene plays an important role during induction of apoptosis in cancer. In contrast, NF-kappaB prevents apoptosis in response to chemotherapeutic agents and is a critical regulator of cell survival. Despite the riches of information on the regulation of wild-type p53 function by phosphorylation, nothing is known about the modulation of mutant p53 activity by phosphorylation. Here we report that inhibition of NF-kappaB in DU145 prostate cancer cells results in p53 mutant phosphorylation at serine 15 (Ser15), leading to an increase of p53 stability, DNA binding and gain of function. Serine 15-phosphorylation is due to GADD45alpha-dependent induction of JNK kinase, which can be blocked by SP600125, a JNK kinase inhibitor. Furthermore, inhibition of GADD45alpha by small interfering RNA blocks JNK activation and abrogates Ser15 phosphorylation. Together, these results highlight the importance of Ser15 phosphorylation in regulating the oncogenic function of mutant p53 and apoptosis induction in the context of the NF-kappaB/IkappaB signaling pathway.

Adenoviridae↗

PubMed2007

Statins induce S1P1 receptors and enhance endothelial nitric oxide production in response to high-density lipoproteins.

BACKGROUND AND PURPOSE: Sphingosine 1-phosphate (S1P) is a serum-borne naturally occurring sphingolipid, specifically enriched in high-density lipoprotein (HDL) fractions. S1P binds to G-protein-coupled S1P1 receptors to activate endothelial NO synthase (eNOS) in vascular endothelial cells. We explored whether and how statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, modulate expression of S1P1 receptors and endothelial responses for subsequent stimulation with S1P or with HDL. EXPERIMENTAL APPROACH: Protein expression and phosphorylation and mRNA expression in cultured bovine aortic endothelial cells (BAEC) were determined using immunoblots and reverse transcription PCR analyses, respectively. NO synthesis was assessed as nitrite production. KEY RESULTS: Stimulation of BAEC with pitavastatin or atorvastatin led to significant increases in S1P1-receptors, at levels of protein and mRNA, in a dose-dependent manner. When BAEC were treated with pitavastatin prior to stimulation with S1P or with normal human HDL, phosphorylation and activation of eNOS evoked by S1P or by HDL was enhanced. These effects of statins were counteracted by L-mevalonate and were mimicked by an inhibitor of geranylgeranyl transferase I, suggesting that inhibition of HMG-CoA reductase activity and subsequent decreases in protein geranylgeranylation may contribute to these actions of statins. Specific knock down of S1P1 receptors by small interfering RNA led to attenuation of eNOS responses to HDL. CONCLUSIONS AND IMPLICATIONS: Statins induce S1P1 receptors and potentiate responses of endothelial cells to HDL-associated sphingolipids, identifying a novel aspect of the pleiotropic actions of statins through which they may exert NO-dependent vascular protective effects.

Alkyl and Aryl Transferases↗

PubMed2003

Cell cycle-dependent regulation of the Skp2 promoter by GA-binding protein.

Skp2 is the F-box protein component of an SCF-type ubiquitin ligase that interacts specifically with p27(Kip1) and thereby promotes its ubiquitylation and degradation. The abundance of Skp2 mRNA oscillates in a cell cycle-dependent manner, being maximal in S and G(2) phases. The regulation of Skp2 transcription was investigated by cloning the promoter region of the mouse gene and determination of its activity in a luciferase reporter assay. Deletion analysis identified a minimal approximately 0.3-kb promoter region with marked transcriptional activity and a 105-bp essential sequence within this region. Electrophoretic mobility shift assays indicated the presence in nuclear extracts of proteins that bind to this sequence. Site-directed mutagenesis revealed that the core binding motif, CACTTCCG, which is similar to that of GA-binding protein (GABP), is essential for Skp2 transcription. "Supershift" analysis indicated that the protein-probe complexes detected by electrophoretic mobility shift assays contain GABP. Endogenous GABP bound to Skp2 promoter element in a cell cycle-dependent manner. Furthermore, overexpression of GABPbeta increased Skp2 promoter activity, and suppression of GABPalpha or GABPbeta by a small interfering RNA resulted in the reduction of Skp2 promoter activity. These data suggest that the cell cycle-dependent binding of GABP to the Skp2 promoter plays an important role in the regulation of Skp2 expression and cell cycle progression from G(1) to S phase.

3T3 Cells↗

PubMed2005

PU.1 silencing leads to terminal differentiation of erythroleukemia cells.

The transcription factor PU.1 plays a central role in development and differentiation of hematopoietic cells. Evidence from PU.1 knockout mice indicates a pivotal role for PU.1 in myeloid lineage and B-lymphocyte development. In addition, PU.1 is a key player in the development of Friend erythroleukemia disease, which is characterized by proliferation and differentiation arrest of proerythrocytes. To study the role of PU.1 in erythroleukemia, we have used murine erythroleukemia cells, isolated from Friend virus-infected mice. Expression of PU.1 small interfering RNA in these cells led to significant inhibition of PU.1 levels. This was accompanied by inhibition of proliferation and restoration in the ability of the proerythroblastic cells to produce hemoglobin, i.e., reversion of the leukemic phenotype. The data suggest that overexpression of PU.1 gene is the immediate cause for maintaining the leukemic phenotype of the disease by retaining the self-renewal capacity of transformed erythroblastic cells and by blocking the terminal differentiation program towards erythrocytes.

Animals↗

PubMed2003

Nitric oxide switches on glycolysis through the AMP protein kinase and 6-phosphofructo-2-kinase pathway.

After inhibition of cytochrome c oxidase by nitric oxide, astrocytes maintain energy production by upregulating glycolysis--a response which does not seem to be available to neurons. Here, we show that in astrocytes, after inhibition of respiration by nitric oxide, there is a rapid, cyclic GMP-independent increase in the activity of 6-phosphofructo-1-kinase (PFK1), a master regulator of glycolysis, and an increase in the concentration of its most powerful positive allosteric activator, fructose-2,6-bisphosphate (F2,6P(2)). In neurons, nitric oxide failed to alter F2,6P(2) concentration or PFK1 activity. This failure could be accounted for by the much lower amount of 6-phosphofructo-2-kinase (PFK2, the enzyme responsible for F2,6P(2) biosynthesis) in neurons. Indeed, full activation of neuronal PFK1 was achieved by adding cytosol from nitric oxide-treated astrocytes. Furthermore, using the small interfering RNA (siRNA) strategy, we demonstrated that the rapid activation of glycolysis by nitric oxide is dependent on phosphorylation of the energy charge-sensitive AMP-activated protein kinase, resulting in activation of PFK2 and protection of cells from apoptosis. Thus the virtual absence of PFK2 in neurons may explain their extreme sensitivity to energy depletion and degeneration.

AMP-Activated Protein Kinases↗

PubMed2002

Biological models and genes of tumor reversion: cellular reprogramming through tpt1/TCTP and SIAH-1.

Tumor reversion is the process by which some cancer cells lose their malignant phenotype. This study was aimed at defining some of the molecular and phenotypic properties of this process. Biological models of tumor reversion were isolated from human leukemia and breast cancer cell lines by using the H-1 parvovirus as a selective agent. Differential gene expression analysis was performed between the parental malignant cells and their revertants or alternatively between these parental cells and their SIAH-1 transfectant counterparts. These SIAH-1 transfectants have a suppressed malignant phenotype and were used as a control for a viral-free system. Two hundred sixty-three genes were found to be either activated or inhibited during the reversion process, as confirmed by Northern blot analysis or quantitative PCR. Of these, 32% were differentially expressed in all systems, irrespective of whether parvovirus-selected, SIAH-1 overexpressing, or p53 mutant or wild-type cell lines were used, suggesting the existence of a universal mechanism underlying tumor reversion. Translationally Controlled Tumor Protein (tpt1/TCTP) has the strongest differential expression, down-regulated in the reversion of U937- and SIAH-1-overexpressing cells. Inhibition of TCTP expression by anti-sense cDNA or small interfering RNA molecules results in suppression of the malignant phenotype and in cellular reorganization, similar to the effect of SIAH-1. Hence, tumor reversion can be defined at the molecular level, not just as the reversal of malignant transformation, but as a biological process in its own right involving a cellular reprogramming mechanism, overriding genetic changes in cancer, by triggering an alternative pathway leading to suppression of tumorigenicity.

Basement Membrane↗

PubMed2003

The cell cycle-regulated protein human GTSE-1 controls DNA damage-induced apoptosis by affecting p53 function.

GTSE-1 (G2 and S phase-expressed-1) protein is specifically expressed during S and G2 phases of the cell cycle. It is mainly localized to the microtubules and when overexpressed delays the G2 to M transition. Here we report that human GTSE-1 (hGTSE-1) protein can negatively regulate p53 transactivation function, protein levels, and p53-dependent apoptosis. We identified a physical interaction between the C-terminal regulatory domain of p53 and the C-terminal region of hGTSE-1 that is necessary and sufficient to down-regulate p53 activity. Furthermore, we provide evidence that hGTSE-1 is able to control p53 function in a cell cycle-dependent fashion. hGTSE-1 knock-down by small interfering RNA resulted in a S/G2-specific increase of p53 levels as well as cell sensitization to DNA damage-induced apoptosis during these phases of the cell cycle. Altogether, this work suggests a physiological role of hGTSE-1 in apoptosis control after DNA damage during S and G2 phases through regulation of p53 function.

Antibodies, Monoclonal↗

PubMed2003

Role of the pleckstrin homology domain of PLCgamma1 in its interaction with the insulin receptor.

A thiol-reactive membrane-associated protein (TRAP) binds covalently to the cytoplasmic domain of the human insulin receptor (IR) beta-subunit when cells are treated with the homobifunctional cross-linker reagent 1,6-bismaleimidohexane. Here, TRAP was found to be phospholipase C gamma1 (PLCgamma1) by mass spectrometry analysis. PLCgamma1 associated with the IR both in cultured cell lines and in a primary culture of rat hepatocytes. Insulin increased PLCgamma1 tyrosine phosphorylation at Tyr-783 and its colocalization with the IR in punctated structures enriched in cortical actin at the dorsal plasma membrane. This association was found to be independent of PLCgamma1 Src homology 2 domains, and instead required the pleckstrin homology (PH)-EF-hand domain. Expression of the PH-EF construct blocked endogenous PLCgamma1 binding to the IR and inhibited insulin-dependent phosphorylation of mitogen-activated protein kinase (MAPK), but not AKT. Silencing PLCgamma1 expression using small interfering RNA markedly reduced insulin-dependent MAPK regulation in HepG2 cells. Conversely, reconstitution of PLCgamma1 in PLCgamma1-/- fibroblasts improved MAPK activation by insulin. Our results show that PLCgamma1 is a thiol-reactive protein whose association with the IR could contribute to the activation of MAPK signaling by insulin.

Animals↗

PubMed2006

CDK2-dependent phosphorylation of FOXO1 as an apoptotic response to DNA damage.

The function of cyclin-dependent kinase 2 (CDK2) is often abolished after DNA damage. The inhibition of CDK2 plays a central role in DNA damage-induced cell cycle arrest and DNA repair. However, whether CDK2 also influences the survival of cells under genotoxic stress is unknown. Forkhead box O (FOXO) transcription factors are emerging as key regulators of cell survival. CDK2 specifically phosphorylated FOXO1 at serine-249 (Ser249) in vitro and in vivo. Phosphorylation of Ser249 resulted in cytoplasmic localization and inhibition of FOXO1. This phosphorylation was abrogated upon DNA damage through the cell cycle checkpoint pathway that is dependent on the protein kinases Chk1 and Chk2. Moreover, silencing of FOXO1 by small interfering RNA diminished DNA damage-induced death in both p53-deficient and p53-proficient cells. This effect was reversed by restored expression of FOXO1 in a manner depending on phosphorylation of Ser249. Functional interaction between CDK2 and FOXO1 provides a mechanism that regulates apoptotic cell death after DNA strand breakage.

Animals↗

PubMed2006

Hepatitis C virus core protein inhibits tumor necrosis factor alpha-mediated apoptosis by a protective effect involving cellular FLICE inhibitory protein.

We have previously shown that hepatitis C virus (HCV) core protein modulates multiple cellular processes, including those that inhibit tumor necrosis factor alpha (TNF-alpha)-mediated apoptosis. In this study, we have investigated the signaling mechanism for inhibition of TNF-alpha-mediated apoptosis in human hepatoma (HepG2) cells expressing core protein alone or in context with other HCV proteins. Activation of caspase-3 and the cleavage of DNA repair enzyme poly(ADP-ribose) polymerase were inhibited upon TNF-alpha exposure in HCV core protein-expressing HepG2 cells. In vivo protein-protein interaction studies displayed an association between TNF receptor 1 (TNFR1) and TNFR1-associated death domain protein (TRADD), suggesting that the core protein does not perturb this interaction. A coimmunoprecipitation assay also suggested that HCV core protein does not interfere with the TRADD-Fas-associated death domain protein (FADD)-procaspase-8 interaction. Further studies indicated that HCV core protein expression inhibits caspase-8 activation by sustaining the expression of cellular FLICE (FADD-like interleukin-1beta-converting enzyme)-like inhibitory protein (c-FLIP). Similar observations were also noted upon expression of core protein in context to other HCV proteins expressed from HCV full-length plasmid DNA or a replicon. A decrease in endogenous c-FLIP by specific small interfering RNA induced TNF-alpha-mediated apoptotic cell death and caspase-8 activation. Taken together, our results suggested that the TNF-alpha-induced apoptotic pathway is inhibited by a sustained c-FLIP expression associated with the expression of HCV core protein, which may play a role in HCV-mediated pathogenesis.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Identification of SK3 channel as a new mediator of breast cancer cell migration.

Potassium channels have been involved in epithelial tumorigenesis but the role of small-conductance Ca(2+)-activated K(+) channels is unknown. We report here that small-conductance Ca(2+)-activated K(+) channels are expressed in a highly metastasizing mammary cancer cell line, MDA-MB-435s. Patch-clamp recordings showed typical small-conductance Ca(2+)-activated K(+) channel-mediated currents sensitive to apamin, 4-aminopyridine, and tetraethylammonium. Moreover, the cells displayed a high intracellular calcium concentration, which was decreased after 24 hours of apamin treatment. By regulating membrane potential and intracellular calcium concentration, these channels were involved in MDA-MB-435s cell migration, but not in proliferation. Only SK3 protein expression was observed in these cells in contrast to SK2, which was expressed both in cancer and noncancer cell lines. Whereas small interfering RNA directed against SK3 almost totally abolished MDA-MB-435s cell migration, transient expression of SK3 increased migration of the SK3-deficient cell lines, MCF-7 and 184A1. SK3 channel was solely expressed in tumor breast biopsies and not in nontumor breast tissues. Thus, SK3 protein channel seems to be a new mediator of breast cancer cell migration and represents a potential target for a new class of anticancer agents.

Biomarkers, Tumor↗

PubMed2005

A new cellular signaling mechanism for angiotensin II activation of NF-kappaB: An IkappaB-independent, RSK-mediated phosphorylation of p65.

OBJECTIVE: Angiotensin II (Ang II) promotes vascular inflammation and remodeling via activation of nuclear factor kappaB (NF-kappaB)-mediated transcription of proinflammatory genes such as interleukin-6 (IL-6). We examined the signaling mechanism whereby Ang II activates NF-kappaB in vascular smooth muscle cells (VSMCs). METHODS AND RESULTS: Ang II treatment did not increase phosphorylation of inhibitor of kappaBalpha (IkappaBalpha) or IkappaBbeta or decrease their levels. In contrast, mitogen-activated protein kinase kinase-1 (MEK1) inhibition (dominant-negative MEK1 adenovirus or inhibitor U0126) suppressed Ang II-induced NF-kappaB promoter activity, NF-kappaB DNA-binding activity, p65 phosphorylation, and led to 70% reduction in IL-6 transcription/production. The mechanism involved Ang II activation of Ras and MEK1. Signaling distal to MEK1 involved extracellular signal-regulated kinase (ERK) because inhibition of MEK1 suppressed the Ang II-induced activation of ribosomal S6 kinase (RSK), a substrate of ERK. Downregulation of RSK by small interfering RNA (SiRNA) in VSMCs was found to suppress Ang II-induced activation of NF-kappaB and p65 phosphorylation. Immunopurified RSK from Ang II-treated VSMCs phosphorylated recombinant glutathione S-transferase-p65 in vitro. CONCLUSIONS: We uncovered a nonclassical signaling pathway (Ras/MEK1/ERK/RSK) from Ang II to activation of NF-kappaB, a mechanism by which Ang II stimulates RSK-mediated phosphorylation of p65 to participate in vascular inflammation.

Angiotensin II↗

PubMed2006

Statins protect human aortic smooth muscle cells from inorganic phosphate-induced calcification by restoring Gas6-Axl survival pathway.

Vascular calcification is clinically important in the development of cardiovascular disease. It is reported that hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (statins) inhibited vascular calcification in several clinical trials. However, the mechanism is poorly understood. Recently, it has been suggested that apoptosis is one of the important processes regulating vascular smooth muscle cell (VSMC) calcification. In this study, we investigated the effect of statins on VSMC calcification by testing their effect on apoptosis, focusing in particular on regulation of the survival pathway mediated by growth arrest-specific gene 6 (Gas6), a member of the vitamin K-dependent protein family, and its receptor, Axl. In human aortic smooth muscle cells (HASMC), statins significantly inhibited inorganic phosphate (Pi)-induced calcification in a concentration-dependent manner (reduced by 49% at 0.1 micromol/L atorvastatin). The inhibitory effect of statins was mediated by preventing apoptosis, which was increased by Pi in a concentration-dependent manner, and not by inhibiting sodium-dependent phosphate cotransporter (NPC) activity, another mechanism regulating HASMC calcification. Furthermore, the antiapoptotic effect of statins was dependent on restoration of Gas6, whose expression was downregulated by Pi. Restoration of Gas6 mRNA by statins was mediated by mRNA stabilization, and not by an increase in transcriptional activity. Suppression of Gas6 using small interfering RNA and the Axl-extracellular domain abolished the preventive effect of statins on Pi-induced apoptosis and calcification. These data demonstrate that statins protected HASMC from Pi-induced calcification by inhibiting apoptosis via restoration of the Gas6-Axl pathway.

Aorta↗

PubMed2004

Neuronal roles of the integrin-associated protein (IAP/CD47) in developing cortical neurons.

Little is known about the role of the integrin-associated protein (IAP, or CD47) in neuronal development and its function in the central nervous system. We investigated neuronal responses in IAP-overexpressing cortical neurons using a virus-gene transfer system. We found that dendritic outgrowth was significantly enhanced in IAP (form 4)-transfected neurons. Furthermore, synaptic proteins including synaptotagmin, syntaxin, synapsin I, and SNAP25 (25-kDa synaptosomal associated protein) were up-regulated. In accordance with this finding, the release of the excitatory transmitter glutamate and the frequencies of Ca2+ oscillations (glutamate-mediated synaptic transmission) were increased. Interestingly, the overexpression of IAP activated mitogen-activated protein kinase (MAPK), and this activation was required for the IAP-dependent biological effects. After down-regulation of the endogenous IAP by small interfering RNA, MAPK activity, synaptic protein levels, and glutamate release decreased. These observations suggest that the IAP plays important roles in dendritic outgrowth and synaptic transmission in developing cortical neurons through the activation of MAPK.

Adenoviridae↗

PubMed2005

The tumor suppressor PTEN is necessary for human Sprouty 2-mediated inhibition of cell proliferation.

Sprouty family proteins are novel regulators of growth factor actions. Human Sprouty 2 (hSPRY2) inhibits the proliferation of a number of different cell types. However, the mechanisms involved in the anti-proliferative actions of hSPRY2 remain to be elucidated. Here we have demonstrated that hSPRY2 increases the amount of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and decreases its phosphorylation. The resultant increase in PTEN activity is reflected in decreased activation of Akt by epidermal growth factor and serum. Consistent with increased PTEN activity, in hSPRY2-expressing cells, the progression of cells from the G1 to S phase is decreased. By using PTEN null primary mouse embryonic fibroblasts and their isogenic controls as well as small interfering RNA against PTEN, we demonstrated that PTEN is necessary for hSPRY2 to inhibit Akt activation by epidermal growth factor as well as cell proliferation. Overall, we concluded that hSPRY2 mediates its anti-proliferative actions by altering PTEN content and activity.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Coordinated transport of phosphorylated amyloid-beta precursor protein and c-Jun NH2-terminal kinase-interacting protein-1.

The transmembrane protein amyloid-beta precursor protein (APP) and the vesicle-associated protein c-Jun NH(2)-terminal kinase-interacting protein-1 (JIP-1) are transported into axons by kinesin-1. Both proteins may bind to kinesin-1 directly and can be transported separately. Because JIP-1 and APP can interact, kinesin-1 may recruit them as a complex, enabling their cotransport. In this study, we tested whether APP and JIP-1 are transported together or separately on different vesicles. We found that, within the cellular context, JIP-1 preferentially interacts with Thr(668)-phosphorylated APP (pAPP), compared with nonphosphorylated APP. In neurons, JIP-1 colocalizes with vesicles containing pAPP and is excluded from those containing nonphosphorylated APP. The accumulation of JIP-1 and pAPP in neurites requires kinesin-1, and the expression of a phosphomimetic APP mutant increases JIP-1 transport. Down-regulation of JIP-1 by small interfering RNA specifically impairs transport of pAPP, with no effect on the trafficking of nonphosphorylated APP. These results indicate that the phosphorylation of APP regulates the formation of a pAPP-JIP-1 complex that accumulates in neurites independent of nonphosphorylated APP.

Adaptor Proteins, Signal Transducing↗