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  • 1.
    Li, Jia
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Shuai, Hongyan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Gylfe, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Oscillations of sub-membrane ATP in glucose-stimulated beta cells depend on negative feedback from Ca2+2013In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 56, no 7, p. 1577-1586Article in journal (Refereed)
    Abstract [en]

    ATP links changes in glucose metabolism to electrical activity, Ca2+ signalling and insulin secretion in pancreatic beta cells. There is evidence that beta cell metabolism oscillates, but little is known about ATP dynamics at the plasma membrane, where regulation of ion channels and exocytosis occur. The sub-plasma-membrane ATP concentration ([ATP](pm)) was recorded in beta cells in intact mouse and human islets using total internal reflection microscopy and the fluorescent reporter Perceval. Glucose dose-dependently increased [ATP](pm) with half-maximal and maximal effects at 5.2 and 9 mmol/l, respectively. Additional elevations of glucose to 11 to 20 mmol/l promoted pronounced [ATP](pm) oscillations that were synchronised between neighbouring beta cells. [ATP](pm) increased further and the oscillations disappeared when voltage-dependent Ca2+ influx was prevented. In contrast, K+-depolarisation induced prompt lowering of [ATP](pm). Simultaneous recordings of [ATP](pm) and the sub-plasma-membrane Ca2+ concentration ([Ca2+](pm)) during the early glucose-induced response revealed that the initial [ATP](pm) elevation preceded, and was temporarily interrupted by the rise of [Ca2+](pm). During subsequent glucose-induced oscillations, the increases of [Ca2+](pm) correlated with lowering of [ATP](pm). In beta cells, glucose promotes pronounced oscillations of [ATP](pm), which depend on negative feedback from Ca2+ (.) The bidirectional interplay between these messengers in the sub-membrane space generates the metabolic and ionic oscillations that underlie pulsatile insulin secretion.

  • 2.
    Tian, Geng
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Sol, Eri Maria
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Xu, Yunjian
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Shuai, Hongyan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Impaired cAMP generation contributes to defective glucose-stimulated insulin secretion after long-term exposure to palmitate2015In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 64, no 3, p. 904-915Article in journal (Refereed)
    Abstract [en]

    Chronic palmitate exposure impairs glucose-stimulated insulin secretion and other aspects of β-cell function but the underlying mechanisms are not known. Using various live-cell fluorescence imaging approaches we show here that long-term palmitate treatment influences cAMP signaling in pancreatic β-cells. Glucose stimulation of mouse and human β-cells induced oscillations of the sub-plasma-membrane cAMP concentration but after 48 h exposure to palmitate, most β-cells failed to increase cAMP in response to glucose. In contrast, GLP-1-triggered cAMP formation and glucose- and depolarization-induced increases in cytoplasmic Ca2+ concentration were unaffected by the fatty acid treatment. Insulin secretion from control β-cells was pulsatile but the response deteriorated after long-term palmitate exposure. Palmitate-treated mouse islets showed reduced expression of adenylyl cyclase 9 and knockdown of this protein in insulinoma cells reduced the glucose-stimulated cAMP response and insulin secretion. We conclude that impaired glucose-induced generation of cAMP is an important determinant of defective insulin secretion after chronic palmitate exposure.

  • 3.
    Tian, Geng
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Sågetorp, Jenny
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Xu, Yunjian
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Shuai, Hongyan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Degerman, Eva
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Role of phosphodiesterases in the shaping of sub-plasma-membrane cAMP oscillations and pulsatile insulin secretion2012In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 125, no 21, p. 5084-5095Article in journal (Refereed)
    Abstract [en]

    Specificity and versatility in cyclic AMP (cAMP) signalling are governed by the spatial localisation and temporal dynamics of the signal. Phosphodiesterases (PDEs) are important for shaping cAMP signals by hydrolyzing the nucleotide. In pancreatic β-cells, glucose triggers sub-plasma-membrane cAMP oscillations, which are important for insulin secretion, but the mechanisms underlying the oscillations are poorly understood. Here, we investigated the role of different PDEs in the generation of cAMP oscillations by monitoring the concentration of cAMP in the sub-plasma-membrane space ([cAMP](pm)) with ratiometric evanescent wave microscopy in MIN6 cells or mouse pancreatic β-cells expressing a fluorescent translocation biosensor. The general PDE inhibitor IBMX increased [cAMP](pm), and whereas oscillations were frequently observed at 50 µM IBMX, 300 µM-1 mM of the inhibitor caused a stable increase in [cAMP](pm). The [cAMP](pm) was nevertheless markedly suppressed by the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine, indicating IBMX-insensitive cAMP degradation. Among IBMX-sensitive PDEs, PDE3 was most important for maintaining a low basal level of [cAMP](pm) in unstimulated cells. After glucose induction of [cAMP](pm) oscillations, inhibitors of PDE1, PDE3 and PDE4 inhibitors the average cAMP level, often without disturbing the [cAMP](pm) rhythmicity. Knockdown of the IBMX-insensitive PDE8B by shRNA in MIN6 cells increased the basal level of [cAMP](pm) and prevented the [cAMP](pm)-lowering effect of 2',5'-dideoxyadenosine after exposure to IBMX. Moreover, PDE8B-knockdown cells showed reduced glucose-induced [cAMP](pm) oscillations and loss of the normal pulsatile pattern of insulin secretion. It is concluded that [cAMP](pm) oscillations in β-cells are caused by periodic variations in cAMP generation, and that several PDEs, including PDE1, PDE3 and the IBMX-insensitive PDE8B, are required for shaping the sub-membrane cAMP signals and pulsatile insulin release.

  • 4.
    Yu, Qian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Shuai, Hongyan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Ahooghalandari, Parvin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Gylfe, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Glucose lowers cAMP to inhibit glucagon secretion by a direct effect on alpha cells2016In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 59, p. S266-S267Article in journal (Refereed)
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