The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform

Robert Zorec - One of the best experts on this subject based on the ideXlab platform.

  • Rosiglitazone Balances Insulin-Induced Exo- And Endocytosis In Single 3t3-L1 Adipocytes
    Molecular and Cellular Endocrinology, 2011
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Rosiglitazone (Rosi) improves insulin sensitivity and increases the translocation of glucose transporter 4 (GLUT4) to the plasma Membrane (PM). This involves the fusion of Membrane-bound compartments with the plasma Membrane, thus increasing the plasma Membrane Area. However, recent work has shown that in Rosi-pretreated 3T3-L1 adipocytes Membrane Area did not increase following insulin application, suggesting that the rates of exo- and endocytosis are balanced. Here we examined whether Rosi differentially affects the rates of exo- and endocytosis in 3T3-L1 adipocytes. The immunolabelling of GLUT4 revealed the 3.1-fold increase in PM-resident GLUT4 in Rosi-pretreated, insulin-stimulated cells. By monitoring cumulative exocytosis and endocytosis we found that in Rosi-pretreated cells insulin substantially stimulated the rate of exocytosis and to a similar extent also the rate of endocytosis. We conclude that Rosi-pretreatment balances insulin-stimulated exocytosis and endocytosis, which may prevent insulin-mediated adipocyte cell size increase.

  • Rosiglitazone Modulates Insulin-Induced Plasma Membrane Area Changes in Single 3T3-L1 Adipocytes
    The Journal of membrane biology, 2008
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Sonja Grilc, Petra Brina Kovacic, Mateja Prebil, Marko Kreft, Jørgen Jensen, Esma R. Isenovic, Robert Zorec
    Abstract:

    In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator–activated receptor γ, affects the plasma Membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in Membrane capacitance (Cm), a parameter linearly related to the PM Area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O–stained Area (11.4 ± 1.2%) vs. controls (3.1 ± 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 ± 1.1 μm in controls was reduced to 17.5 ± 0.5 μm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of Cm increase to 2.34 ± 0.10%/min, which was significantly different from controls (0.12 ± 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of Cm increase. These data support the involvement of insulin in the modulation of Membrane Area and show that treatment by rosiglitazone reduced the insulin-mediated Membrane Area increase in 3T3-L1 adipocytes.

  • Endocytosis-dominated Membrane Area decrease requires Rab5 protein in rat melanotrophs.
    Annals of the New York Academy of Sciences, 2005
    Co-Authors: Simon Sedej, Marjan Rupnik, Robert Zorec
    Abstract:

    Eukaryotic cells internalize extracellular macromolecules by en- docytosis and it was shown that Rab5 protein is required for this process. While it is clear that endocytosis consists of vesicle fission from the plasma mem- brane, the role of Rab5 protein in the plasma Membrane surface Area changes is still unclear. Here we studied whether Rab5 is required for Membrane sur- face Area changes in rat melanotrophs—cells deriving from the pituitary pars intermedia. The presence of this protein in melanotrophs was probed by immu- nocytochemistry and its putative role in Membrane Area dynamics was moni- tored electrophysiologically with Membrane capacitance measurements as this parameter directly reflects changes in Membrane surface Area. We found that Rab5 protein exists in melanotrophs. At (Ca 2+ )i < 3 M, endocytosis-dominat- ed Membrane capacitance decrease was found to be blocked by microinjection of specific Rab5 antibody. At high (Ca 2+ )i, Rab5 antibody did not affect the steady-state increase in Membrane capacitance, while it elevated the rate of Membrane capacitance increase, which is consistent with an inhibition of en- docytosis.

  • Correlated ATP-induced changes in Membrane Area and Membrane conductance in single rat adipocytes.
    Annals of the New York Academy of Sciences, 2005
    Co-Authors: Helena H. Chowdhury, Sonja Grilc, Robert Zorec
    Abstract:

    In the past few years it has been shown that, like many other non-neuroendocrine cells, adipocytes possess a mechanism for triggered exocytosis. Endocytosis and exocytosis affect the plasma Membrane surface Area, which can be directly monitored with electrophysiological patch-clamp techniques by measuring Membrane capacitance, a parameter linearly related to the plasma Membrane Area. In this study we used the whole-cell mode of the patch-clamp technique to measure changes in Membrane capacitance to monitor the effect of extracellular adenosine triphosphate (ATP) on the dynamics of Membrane Area changes in single adipocytes. Experimental evidence shows that extracellular application of ATP (100 microM) increases Membrane capacitance for 30 +/- 2%. In controls a significantly smaller increase of 3 +/- 2% was measured, which is due to a slow exocytic-endocytic Membrane cycling rate of 0.3%/min. We found that ATP induces a transient increase in Membrane current, temporally associated with the peak rate in Membrane capacitance increase. These results show directly the presence of ATP-induced increase in Membrane Area correlated to the increase in Membrane current in single adipocytes.

  • Rapid insulin-induced exocytosis in white rat adipocytes.
    Pflugers Archiv : European journal of physiology, 2002
    Co-Authors: Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Insulin is believed to increase glucose permeability of adipocytes by regulating the incorporation of glucose transporters into the plasma Membrane by exocytosis. This process involves fusion of Membrane-bound cellular compartments with the plasma Membrane, thus influencing the plasma Membrane Area. However, insulin-induced changes in plasma Membrane Area have not yet been demonstrated. In the present study we monitored fluorescence intensity with a confocal microscope to study the effect of insulin on adipocyte plasma Membrane Area. After cell isolation and adhesion to a glass cover-slip, adipocytes were stained with the dye FM1-43, a Membrane Area reporter. At rest, the rate of fluorescence intensity increase was initially high, but gradually stabilized at 2%/min. This steady increase in fluorescence is due to a slow rate of exocytosis coupled to endocytosis, since the removal of FM1-43 from the bath did not abolish FM1-43 fluorescence. Insulin addition caused an abrupt increase of fluorescence intensity of 4%/min, which was significantly higher than in controls. These results suggest rapid, insulin-induced incorporation of new Membrane into the plasma Membrane by exocytosis.

Helena H. Chowdhury - One of the best experts on this subject based on the ideXlab platform.

  • Rosiglitazone Balances Insulin-Induced Exo- And Endocytosis In Single 3t3-L1 Adipocytes
    Molecular and Cellular Endocrinology, 2011
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Rosiglitazone (Rosi) improves insulin sensitivity and increases the translocation of glucose transporter 4 (GLUT4) to the plasma Membrane (PM). This involves the fusion of Membrane-bound compartments with the plasma Membrane, thus increasing the plasma Membrane Area. However, recent work has shown that in Rosi-pretreated 3T3-L1 adipocytes Membrane Area did not increase following insulin application, suggesting that the rates of exo- and endocytosis are balanced. Here we examined whether Rosi differentially affects the rates of exo- and endocytosis in 3T3-L1 adipocytes. The immunolabelling of GLUT4 revealed the 3.1-fold increase in PM-resident GLUT4 in Rosi-pretreated, insulin-stimulated cells. By monitoring cumulative exocytosis and endocytosis we found that in Rosi-pretreated cells insulin substantially stimulated the rate of exocytosis and to a similar extent also the rate of endocytosis. We conclude that Rosi-pretreatment balances insulin-stimulated exocytosis and endocytosis, which may prevent insulin-mediated adipocyte cell size increase.

  • Rosiglitazone Modulates Insulin-Induced Plasma Membrane Area Changes in Single 3T3-L1 Adipocytes
    The Journal of membrane biology, 2008
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Sonja Grilc, Petra Brina Kovacic, Mateja Prebil, Marko Kreft, Jørgen Jensen, Esma R. Isenovic, Robert Zorec
    Abstract:

    In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator–activated receptor γ, affects the plasma Membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in Membrane capacitance (Cm), a parameter linearly related to the PM Area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O–stained Area (11.4 ± 1.2%) vs. controls (3.1 ± 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 ± 1.1 μm in controls was reduced to 17.5 ± 0.5 μm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of Cm increase to 2.34 ± 0.10%/min, which was significantly different from controls (0.12 ± 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of Cm increase. These data support the involvement of insulin in the modulation of Membrane Area and show that treatment by rosiglitazone reduced the insulin-mediated Membrane Area increase in 3T3-L1 adipocytes.

  • Correlated ATP-induced changes in Membrane Area and Membrane conductance in single rat adipocytes.
    Annals of the New York Academy of Sciences, 2005
    Co-Authors: Helena H. Chowdhury, Sonja Grilc, Robert Zorec
    Abstract:

    In the past few years it has been shown that, like many other non-neuroendocrine cells, adipocytes possess a mechanism for triggered exocytosis. Endocytosis and exocytosis affect the plasma Membrane surface Area, which can be directly monitored with electrophysiological patch-clamp techniques by measuring Membrane capacitance, a parameter linearly related to the plasma Membrane Area. In this study we used the whole-cell mode of the patch-clamp technique to measure changes in Membrane capacitance to monitor the effect of extracellular adenosine triphosphate (ATP) on the dynamics of Membrane Area changes in single adipocytes. Experimental evidence shows that extracellular application of ATP (100 microM) increases Membrane capacitance for 30 +/- 2%. In controls a significantly smaller increase of 3 +/- 2% was measured, which is due to a slow exocytic-endocytic Membrane cycling rate of 0.3%/min. We found that ATP induces a transient increase in Membrane current, temporally associated with the peak rate in Membrane capacitance increase. These results show directly the presence of ATP-induced increase in Membrane Area correlated to the increase in Membrane current in single adipocytes.

  • Rapid insulin-induced exocytosis in white rat adipocytes.
    Pflugers Archiv : European journal of physiology, 2002
    Co-Authors: Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Insulin is believed to increase glucose permeability of adipocytes by regulating the incorporation of glucose transporters into the plasma Membrane by exocytosis. This process involves fusion of Membrane-bound cellular compartments with the plasma Membrane, thus influencing the plasma Membrane Area. However, insulin-induced changes in plasma Membrane Area have not yet been demonstrated. In the present study we monitored fluorescence intensity with a confocal microscope to study the effect of insulin on adipocyte plasma Membrane Area. After cell isolation and adhesion to a glass cover-slip, adipocytes were stained with the dye FM1-43, a Membrane Area reporter. At rest, the rate of fluorescence intensity increase was initially high, but gradually stabilized at 2%/min. This steady increase in fluorescence is due to a slow rate of exocytosis coupled to endocytosis, since the removal of FM1-43 from the bath did not abolish FM1-43 fluorescence. Insulin addition caused an abrupt increase of fluorescence intensity of 4%/min, which was significantly higher than in controls. These results suggest rapid, insulin-induced incorporation of new Membrane into the plasma Membrane by exocytosis.

Jelena Velebit - One of the best experts on this subject based on the ideXlab platform.

  • Rosiglitazone Balances Insulin-Induced Exo- And Endocytosis In Single 3t3-L1 Adipocytes
    Molecular and Cellular Endocrinology, 2011
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Rosiglitazone (Rosi) improves insulin sensitivity and increases the translocation of glucose transporter 4 (GLUT4) to the plasma Membrane (PM). This involves the fusion of Membrane-bound compartments with the plasma Membrane, thus increasing the plasma Membrane Area. However, recent work has shown that in Rosi-pretreated 3T3-L1 adipocytes Membrane Area did not increase following insulin application, suggesting that the rates of exo- and endocytosis are balanced. Here we examined whether Rosi differentially affects the rates of exo- and endocytosis in 3T3-L1 adipocytes. The immunolabelling of GLUT4 revealed the 3.1-fold increase in PM-resident GLUT4 in Rosi-pretreated, insulin-stimulated cells. By monitoring cumulative exocytosis and endocytosis we found that in Rosi-pretreated cells insulin substantially stimulated the rate of exocytosis and to a similar extent also the rate of endocytosis. We conclude that Rosi-pretreatment balances insulin-stimulated exocytosis and endocytosis, which may prevent insulin-mediated adipocyte cell size increase.

  • Rosiglitazone Modulates Insulin-Induced Plasma Membrane Area Changes in Single 3T3-L1 Adipocytes
    The Journal of membrane biology, 2008
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Sonja Grilc, Petra Brina Kovacic, Mateja Prebil, Marko Kreft, Jørgen Jensen, Esma R. Isenovic, Robert Zorec
    Abstract:

    In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator–activated receptor γ, affects the plasma Membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in Membrane capacitance (Cm), a parameter linearly related to the PM Area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O–stained Area (11.4 ± 1.2%) vs. controls (3.1 ± 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 ± 1.1 μm in controls was reduced to 17.5 ± 0.5 μm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of Cm increase to 2.34 ± 0.10%/min, which was significantly different from controls (0.12 ± 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of Cm increase. These data support the involvement of insulin in the modulation of Membrane Area and show that treatment by rosiglitazone reduced the insulin-mediated Membrane Area increase in 3T3-L1 adipocytes.

Marko Kreft - One of the best experts on this subject based on the ideXlab platform.

  • Rosiglitazone Balances Insulin-Induced Exo- And Endocytosis In Single 3t3-L1 Adipocytes
    Molecular and Cellular Endocrinology, 2011
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Rosiglitazone (Rosi) improves insulin sensitivity and increases the translocation of glucose transporter 4 (GLUT4) to the plasma Membrane (PM). This involves the fusion of Membrane-bound compartments with the plasma Membrane, thus increasing the plasma Membrane Area. However, recent work has shown that in Rosi-pretreated 3T3-L1 adipocytes Membrane Area did not increase following insulin application, suggesting that the rates of exo- and endocytosis are balanced. Here we examined whether Rosi differentially affects the rates of exo- and endocytosis in 3T3-L1 adipocytes. The immunolabelling of GLUT4 revealed the 3.1-fold increase in PM-resident GLUT4 in Rosi-pretreated, insulin-stimulated cells. By monitoring cumulative exocytosis and endocytosis we found that in Rosi-pretreated cells insulin substantially stimulated the rate of exocytosis and to a similar extent also the rate of endocytosis. We conclude that Rosi-pretreatment balances insulin-stimulated exocytosis and endocytosis, which may prevent insulin-mediated adipocyte cell size increase.

  • Rosiglitazone Modulates Insulin-Induced Plasma Membrane Area Changes in Single 3T3-L1 Adipocytes
    The Journal of membrane biology, 2008
    Co-Authors: Jelena Velebit, Helena H. Chowdhury, Sonja Grilc, Petra Brina Kovacic, Mateja Prebil, Marko Kreft, Jørgen Jensen, Esma R. Isenovic, Robert Zorec
    Abstract:

    In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator–activated receptor γ, affects the plasma Membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in Membrane capacitance (Cm), a parameter linearly related to the PM Area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O–stained Area (11.4 ± 1.2%) vs. controls (3.1 ± 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 ± 1.1 μm in controls was reduced to 17.5 ± 0.5 μm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of Cm increase to 2.34 ± 0.10%/min, which was significantly different from controls (0.12 ± 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of Cm increase. These data support the involvement of insulin in the modulation of Membrane Area and show that treatment by rosiglitazone reduced the insulin-mediated Membrane Area increase in 3T3-L1 adipocytes.

  • Rapid insulin-induced exocytosis in white rat adipocytes.
    Pflugers Archiv : European journal of physiology, 2002
    Co-Authors: Helena H. Chowdhury, Marko Kreft, Robert Zorec
    Abstract:

    Insulin is believed to increase glucose permeability of adipocytes by regulating the incorporation of glucose transporters into the plasma Membrane by exocytosis. This process involves fusion of Membrane-bound cellular compartments with the plasma Membrane, thus influencing the plasma Membrane Area. However, insulin-induced changes in plasma Membrane Area have not yet been demonstrated. In the present study we monitored fluorescence intensity with a confocal microscope to study the effect of insulin on adipocyte plasma Membrane Area. After cell isolation and adhesion to a glass cover-slip, adipocytes were stained with the dye FM1-43, a Membrane Area reporter. At rest, the rate of fluorescence intensity increase was initially high, but gradually stabilized at 2%/min. This steady increase in fluorescence is due to a slow rate of exocytosis coupled to endocytosis, since the removal of FM1-43 from the bath did not abolish FM1-43 fluorescence. Insulin addition caused an abrupt increase of fluorescence intensity of 4%/min, which was significantly higher than in controls. These results suggest rapid, insulin-induced incorporation of new Membrane into the plasma Membrane by exocytosis.

Galina V. Beznoussenko - One of the best experts on this subject based on the ideXlab platform.

  • Membrane Curvature, Trans-Membrane Area Asymmetry, Budding, Fission and Organelle Geometry.
    International journal of molecular sciences, 2020
    Co-Authors: Alexander A. Mironov, Anna Mironov, Jure Derganc, Galina V. Beznoussenko
    Abstract:

    In biology, the modern scientific fashion is to mostly study proteins. Much less attention is paid to lipids. However, lipids themselves are extremely important for the formation and functioning of cellular Membrane organelles. Here, the role of the geometry of the lipid bilayer in regulation of organelle shape is analyzed. It is proposed that during rapid shape transition, the number of lipid heads and their size (i.e., due to the change in lipid head charge) inside lipid leaflets modulates the geometrical properties of organelles, in particular their Membrane curvature. Insertion of proteins into a lipid bilayer and the shape of protein trans-Membrane domains also affect the trans-Membrane asymmetry between surface Areas of luminal and cytosol leaflets of the Membrane. In the cases where lipid molecules with a specific shape are not predominant, the shape of lipids (cylindrical, conical, or wedge-like) is less important for the regulation of Membrane curvature, due to the flexibility of their acyl chains and their high ability to diffuse.

  • Trans-Membrane Area Asymmetry Controls the Shape of Cellular Organelles
    International Journal of Molecular Sciences, 2015
    Co-Authors: Galina V. Beznoussenko, Jure Derganc, Sergei Pilyugin, Willie Geerts, Michael Kozlov, Koert Burger, Alberto Luini, Alexander Mironov
    Abstract:

    Membrane organelles often have complicated shapes and differ in their volume, surface Area and Membrane curvature. The ratio between the surface Area of the cytosolic and luminal leaflets (trans-Membrane Area asymmetry (TAA)) determines the Membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface Area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of Membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of Membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface Area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these Membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant