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  • Noncell-autonomous photoreceptor degeneration in a zebrafish model of choroideremia. 17360570

    Choroideremia is an X-linked hereditary retinal degeneration resulting from mutations in the Rab escort protein-1 (REP1). The Rep1 protein facilitates posttranslational modification of Rab proteins, which regulate intracellular trafficking in the retinal pigment epithelium (RPE) and photoreceptors and are likely involved in the removal of outer segment disk membranes by the RPE. A critical question for potential treatment of choroideremia is whether photoreceptor degeneration results from autonomous defects in opsin transport within the photoreceptor or as a nonautonomous and secondary consequence of RPE degeneration. To address this question, we have characterized the retinal pathology in zebrafish rep1 mutants, which carry a recessive nonsense mutation in the REP1 gene. Zebrafish rep1 mutants exhibit degeneration of the RPE and photoreceptors and complete loss of visual function as measured by electroretinograms. In the mutant RPE, photoreceptor outer segment material was not effectively eliminated, and large vacuoles were observed. However, opsin trafficking in photoreceptors occurred normally. Mosaic analysis revealed that photoreceptor degeneration was nonautonomous and required contact with the mutant RPE as mutant photoreceptors were rescued in wild-type hosts and wild-type photoreceptors degenerated in mutant hosts. We conclude that mutations in REP1 disrupt cellular processes in the RPE, which causes photoreceptor death as a secondary consequence. These results suggest that therapies that correct the RPE may successfully rescue photoreceptor loss in choroideremia.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB1783
    Nombre del producto:
    Anti-Glutamate Transporter Antibody, Glial
  • AS160 deficiency causes whole-body insulin resistance via composite effects in multiple tissues. 23078342

    AS160 (Akt substrate of 160 kDa) is a Rab GTPase-activating protein implicated in insulin control of GLUT4 (glucose transporter 4) trafficking. In humans, a truncation mutation (R363X) in one allele of AS160 decreased the expression of the protein and caused severe postprandial hyperinsulinaemia during puberty. To complement the limited studies possible in humans, we generated an AS160-knockout mouse. In wild-type mice, AS160 expression is relatively high in adipose tissue and soleus muscle, low in EDL (extensor digitorum longus) muscle and detectable in liver only after enrichment. Despite having lower blood glucose levels under both fasted and random-fed conditions, the AS160-knockout mice exhibited insulin resistance in both muscle and liver in a euglycaemic clamp study. Consistent with this paradoxical phenotype, basal glucose uptake was higher in AS160-knockout primary adipocytes and normal in isolated soleus muscle, but their insulin-stimulated glucose uptake and overall GLUT4 levels were markedly decreased. In contrast, insulin-stimulated glucose uptake and GLUT4 levels were normal in EDL muscle. The liver also contributes to the AS160-knockout phenotype via hepatic insulin resistance, elevated hepatic expression of phosphoenolpyruvate carboxykinase isoforms and pyruvate intolerance, which are indicative of increased gluconeogenesis. Overall, as well as its catalytic function, AS160 influences expression of other proteins, and its loss deregulates basal and insulin-regulated glucose homoeostasis, not only in tissues that normally express AS160, but also by influencing liver function.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-741
    Nombre del producto:
    Anti-AS160 (Rab-GAP) Antibody
  • Calmodulin binds to the Rab GTPase activating protein required for insulin-stimulated GLUT4 translocation. 16055084

    Recently, we described a 160 kDa protein with a Rab GTPase activating protein domain that is phosphorylated on multiple sites by the protein kinase Akt (designated AS160). Phosphorylation of AS160 in adipocytes is required for insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane. In the present study, we searched for proteins that interact with the GTPase activating protein (GAP) domain region of AS160 by the yeast two-hybrid screen. This search indicated that calmodulin bound to a small domain just amino terminal to the GAP domain of AS160, and this association has been confirmed by three other methods, including co-immunoprecipitation from lysates of adipocytes. The association was Ca ion dependent. The role of calmodulin binding to AS160 in insulin-stimulated GLUT4 translocation was examined through the generation of a point mutant of AS160 that did not bind calmodulin. This mutation did not interfere with the capacity of AS160 lacking Akt phosphorylation sites to inhibit GLUT4 translocation. Consequently, calmodulin binding is probably not required for the participation of AS160 in insulin-stimulated GLUT4 translocation.
    Tipo de documento:
    Referencia
    Referencia del producto:
    05-173
    Nombre del producto:
    Anti-Calmodulin Antibody
  • Family-wide characterization of the DENN domain Rab GDP-GTP exchange factors. 20937701

    A key requirement for Rab function in membrane trafficking is site-specific activation by GDP-GTP exchange factors (GEFs), but the majority of the 63 human Rabs have no known GEF. We have performed a systematic characterization of the 17 human DENN domain proteins and demonstrated that they are specific GEFs for 10 Rabs. DENND1A/1B localize to clathrin patches at the plasma membrane and activate Rab35 in an endocytic pathway trafficking Shiga toxin to the trans-Golgi network. DENND2 GEFs target to actin filaments and control Rab9-dependent trafficking of mannose-6-phosphate receptor to lysosomes. DENND4 GEFs target to a tubular membrane compartment adjacent to the Golgi, where they activate Rab10, which suggests a function in basolateral polarized sorting in epithelial cells that compliments the non-DENN GEF Sec2 acting on Rab8 in apical sorting. DENND1C, DENND3, DENND5A/5B, MTMR5/13, and MADD activate Rab13, Rab12, Rab39, Rab28, and Rab27A/27B, respectively. Together, these findings provide a basis for future studies on Rab regulation and function.
    Tipo de documento:
    Referencia
    Referencia del producto:
    CBL47
  • PKB-Mediated Thr649 Phosphorylation of AS160/TBC1D4 Regulates the R-Wave Amplitude in the Heart. 25923736

    The Rab GTPase activating protein (RabGAP), AS160/TBC1D4, is an important substrate of protein kinase B (PKB), and regulates insulin-stimulated trafficking of glucose transporter 4. Besides, AS160/TBC1D4 has also been shown to regulate trafficking of many other membrane proteins including FA translocase/CD36 in cardiomyocytes. However, it is not clear whether it plays any role in regulating heart functions in vivo. Here, we found that PKB-mediated phosphorylation of Thr649 on AS160/TBC1D4 represented one of the major PAS-binding signals in the heart in response to insulin. Mutation of Thr649 to a non-phosphorylatable alanine increased the R-wave amplitude in the AS160Thr649Ala knockin mice. However, this knockin mutation did not affect the heart functions under both normal and infarct conditions. Interestingly, myocardial infarction induced the expression of a related RabGAP, TBC1D1, in the infarct zone as well as in the border zone. Together, these data show that the Thr649 phosphorylation of AS160/TBC1D4 plays an important role in the heart's electrical conduction system through regulating the R-wave amplitude.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-741
    Nombre del producto:
    Anti-AS160 (Rab-GAP) Antibody
  • Rab14 and its exchange factor FAM116 link endocytic recycling and adherens junction stability in migrating cells. 22595670

    Rab GTPases define the vesicle trafficking pathways underpinning cell polarization and migration. Here, we find that Rab4, Rab11, and Rab14 and the candidate Rab GDP-GTP exchange factors (GEFs) FAM116A and AVL9 are required for cell migration. Rab14 and its GEF FAM116A localize to and act on an intermediate compartment of the transferrin-recycling pathway prior to Rab11 and after Rab5 and Rab4. This Rab14 intermediate recycling compartment has specific functions in migrating cells discrete from early and recycling endosomes. Rab14-depleted cells show increased N-cadherin levels at junctional complexes and cannot resolve cell-cell junctions. This is due to decreased shedding of cell-surface N-cadherin by the ADAM family protease ADAM10/Kuzbanian. In FAM116A- and Rab14-depleted cells, ADAM10 accumulates in a transferrin-positive endocytic compartment, and the cell-surface level of ADAM10 is correspondingly reduced. FAM116 and Rab14 therefore define an endocytic recycling pathway needed for ADAM protease trafficking and regulation of cell-cell junctions.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo
  • Transport to late endosomes is required for efficient reovirus infection. 22674975

    Rab GTPases play an essential role in vesicular transport by coordinating the movement of various types of cargo from one cellular compartment to another. Individual Rab GTPases are distributed to specific organelles and thus serve as markers for discrete types of endocytic vesicles. Mammalian reovirus binds to cell surface glycans and junctional adhesion molecule-A (JAM-A) and enters cells by receptor-mediated endocytosis in a process dependent on β1 integrin. Within organelles of the endocytic compartment, reovirus undergoes stepwise disassembly catalyzed by cathepsin proteases, which allows the disassembly intermediate to penetrate endosomal membranes and release the transcriptionally active viral core into the cytoplasm. The pathway used by reovirus to traverse the endocytic compartment is largely unknown. In this study, we found that reovirus particles traffic through early, late, and recycling endosomes during cell entry. After attachment to the cell surface, reovirus particles and JAM-A codistribute into each of these compartments. Transfection of cells with constitutively active and dominant-negative Rab GTPases that affect early and late endosome biogenesis and maturation influenced reovirus infectivity. In contrast, reovirus infectivity was not altered in cells expressing mutant Rab GTPases that affect recycling endosomes. Thus, reovirus virions localize to early, late, and recycling endosomes during entry into host cells, but only those that traverse early and late endosomes yield a productive infection.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB2253Z
    Nombre del producto:
    Anti-Integrin β1 Antibody, clone 6S6, Azide Free
  • Rab proteins mediate Golgi transport of caveola-internalized glycosphingolipids and correct lipid trafficking in Niemann-Pick C cells. 12070301

    We recently showed that human skin fibroblasts internalize fluorescent analogues of the glycosphingolipids lactosylceramide and globoside almost exclusively by a clathrin-independent mechanism involving caveolae. In contrast, a sphingomyelin analogue is internalized approximately equally via clathrin-dependent and caveolar routes. Here, we further characterized the caveolar pathway for glycosphingolipids, showing that Golgi targeting of sphingolipids internalized via caveolae required microtubules and phosphoinositol 3-kinases and was inhibited in cells expressing dominant-negative Rab7 and Rab9 constructs. In addition, overexpression of wild-type Rab7 or Rab9 (but not Rab11) in Niemann-Pick type C (NP-C) lipid storage disease fibroblasts resulted in correction of lipid trafficking defects, including restoration of Golgi targeting of fluorescent lactosylceramide and endogenous GM(1) ganglioside, and a dramatic reduction in intracellular cholesterol stores. Our results demonstrate a role for Rab7 and Rab9 in the Golgi targeting of glycosphingolipids and suggest a new therapeutic approach for restoring normal lipid trafficking in NP-C cells.
    Tipo de documento:
    Referencia
    Referencia del producto:
    05-853